Surface electromyography (sEMG) has been the subject of thousands of scientific articles, but many barriers limit its clinical applications. Previous work has indicated that the lack of time, competence, training, and teaching is the main barrier to the clinical application of sEMG. This work follows up and presents a number of analogies, metaphors, and simulations using physical and mathematical models that provide tools for teaching sEMG detection by means of electrode pairs  and electrode grids . The basic mechanisms of sEMG generation are summarized and the features of the sensing system  are illustrated (mostly by animations) with examples that teachers can use. The most common, as well as some potential, applications are illustrated in the areas of signal presentation, gait analysis, the optimal injection of botulinum toxin, neurorehabilitation, ergonomics, obstetrics, occupational medicine, and sport sciences. The work is primarily focused on correct sEMG detection and on crosstalk. Issues related to the clinical transfer of innovations are also discussed, as well as the need for training new clinical and/or technical operators in the field of sEMG. Bioelectric signals are the results of the activity of organs that are made of excitable cells, such as the brain, the heart or a muscle. Electrical currents flow through the membranes of these cells and generate action potentials that travel along axons or muscle fibers, triggering other events within or between the cells . The electric fields generated by these action potentials produce a distribution of electric potential in space, on the skin, that evolves over time, as with a movie.Our eyes cannot see these distributions of voltage or their time evolution on the scalp , on the chest  or on a muscle , but instruments can and they can visualize them as colored images that we can see and interpret in the same way as thermal images describing temperature distributions over surfaces. To obtain images of voltage distribution, grids of contact points (electrodes) are applied to the chest, scalp or on a muscle, as indicated in Bioelectric signals and images provide an extraordinary opportunity to discover and quantify a wealth of physiological and pathological phenomena that are associated with the organs that generate them. In addition, they provide valuable information to clinicians for functional diagnosis, treatment planning, and the evaluation of the effectiveness of interventions and patient recovery. The role of EEG mapping for studying brain rhythms, the spatial distribution of evoked potentials, epilepsy foci, etc., and the role of ECG mapping in studying atrio-ventricular conduction problems, arrhythmias, etc., are both well known to specialists. The role of sEMG in clinical medicine is less recognized, despite the potential benefits it may offer, mostly because of limited academic teaching . SurfaceThe purpose of this work is to illustrate in a simple way several fundamental concepts that should be understood and recommendations that should be followed concerning the detection modalities of sEMG , electrode locations, etc.) in order to (a) be able to extract the information of interest and (b) apply it clinically. The applications of interest range from gait analysis in neurorehabilitation  to the l(a)overcoming some of the barriers that currently limit the widespread application of sEMG in the clinical world ,18;(b)responding to the persistent demand for the simplification of teaching these concepts;(c)making users aware of the tutorials and teaching materials that are available.This work does not aim to present or discuss advances in sEMG technology. Its goal is to illustrate the current technology, in terms of teaching material, tutorials, and consensus papers, concerning the detection and interpretation of sEMG. This work is aimed at teachers, clinical tutors, and students with the objectives of:https://www.robertomerletti.it/en/emg/material/teaching, where further details can be found. They are presented with the intention of promoting teaching and outlining the improper or incorrect acquisition/interpretation of sEMG.Teaching tools and models are illustrated for this purpose. Some of them were derived from published tutorials ,20 or moThis paper is structured in six sections with the following purposes: Fundamental physiological concepts about sEMG signals, events, and phenomena are reviewed here, together with sEMG modeling techniques that are suitable for teaching, as well as demonstrations.The sEMG voltage distribution on the skin is the sum of the propagating MU action potentials (MUAPs) produced by the recruited MUs. The MU is the basic muscle building block, consisting of one motor neuron and all of the muscle fibers that it innervates. Every time an axonal action potential reaches the neuromuscular junction (NMJ), acetylcholine is released and a muscle fiber action potential is triggered. As indicated in A fundamental difference between sEMG and ECG or EEG is that electrodes placed on the skin, parallel to the muscle fibers, detect the MUAPs that are propagating bidirectionally from the IZs of the MUs to the muscle–tendon junctions. Since the fibers of an MU are of the same histological type and have about the same diameter, their action potentials travel at the same velocity (CV) along the fibers and their contributions add up, on the skin, as MUAPs that provide a “signature” or “fingerprint” for each MU.These MUAPs are the basic building blocks of the sEMG. Understanding sEMG implies the understanding of its generation mechanisms. For this reason, our explanations of the physiological concepts focus mostly on single fiber action potentials and/or on single MUAPs whose sum is the sEMG. It should be noted that with progressively stronger voluntary contractions of a muscle, the information about the individual MUAPs becomes progressively more difficult to extract .Although this may seem a simple and straightforward mechanism that is easy to describe and to teach students, a much deeper analysis is needed to fully understand its details. This is necessary to properly pose and answer the following questions: “What information about the MU properties and their central control strategy can be obtained from the sEMG?” and “When can this information be useful?”.For teaching purposes, simple metaphors and examples may be appropriate. One such example is provided in https://www.robertomerletti.it/en/emg/material/teaching/module9. As is indicated also in Figure 10, the central arrow of the tripole represents positive ions entering the fiber through the open channels and the two lateral arrows represent the positive ions exiting the fiber or negative ions entering it. For the ease of representation and calculation, these ionic currents are modeled as concentrated at three specific points (the tripole).In practice, each muscle fiber can be considered as a line and an action potential moving along it can be approximated by three point-like current sources (a tripole), as described in detail in ,25,26 anA single fiber action potential, or MUAP, produces a two-dimensional wave of electric potential over the skin that moves along the muscle . To summWe now look at the skin from above as the surface of a liquid containing light sources. For simplicity, we now consider a point-like light source that is at some depth in this liquid, which causes a halo to appear on the surface. In the same way, the source of an electric field at some depth below the skin produces a voltage distribution on the skin surface due to diffusion in the “conductive volume” (or “volume conductor”) of the tissue, as indicated in Two point-like light sources (one blue and one red) produce the two partially overlapping halos, as represented in A = V1 − V2V, B = V2 − V3V, … up to Q = V15 − V16V are presented as output signals. Note that these differences are calculated by the 15 differential amplifiers that compute + − V−V. If the linear electrode array were inverted (with Electrode 16 at the top and Electrode 1 at the bottom), the polarity of all signals would be inverted. Note that the two MUs have different IZs, located below Electrodes 7–8 (Channel G) and Electrodes 8–9 (Channel H), and their fibers terminate under the two ends of the linear electrode array. Therefore, it is possible to estimate the MU fiber length, as well as the CVs and the IZs. Note, for MU1, the lack of propagation in the action potentials that are detected by Amplifier A (compared to B) and Amplifier Q (compared to P). This lack of propagation indicates the end of the fibers (better defined later in this subsection) and, therefore, their length spans the distance between Amplifiers B and P. Additionally, note that the channels on one side of the IZ have a polarity while those on the other side have the opposite polarity. The amplitudes of the single differential (SD) signals detected above the IZs are near zero.The electrical image describing the instantaneous distribution of the sEMG voltage is called “monopolar” when the voltage of each point is referred to a remote reference taken as zero  + (V2 − V3)V. Double differential (DD) signals can be obtained from the difference between adjacent SD signals.Note that signals from double (or multiple) IED values may be obtained either by taking the difference between the corresponding monopolar signals or by adding adjacent SD signals, since These are useful properties of differential detection and allow for the easy identification of the IZ of an MU as the region where the action potentials change polarity. This information can have clinical applications see .https://www.robertomerletti.it/en/emg/material/teaching/module5 and https://www.robertomerletti.it/en/emg/material/teaching/module9. This phenomenon is modeled by describing the transmembrane current distribution with a tripole that is made of two opposing dipoles (d1 and d2), as indicated in 1 and t2) and disappears (3), leaving the second dipole d2 whose field is stronger because it is no longer partially canceled by d1. In turn, d2 shrinks (4) and disappears (5). This model explains the presence of non-traveling waves in the monopolar signals, as indicated in When the action potential reaches the end of a muscle fiber, it stops generating a transient signal; this is referred to as the end-of-fiber (EOF) effect, which is described in detail in https://www.robertomerletti.it/en/emg/material/teaching/module9.Despite their many limitations, models of sEMG are powerful teaching tools because they can show, with some approximation, the effects that changing individual fiber (or MU) parameters have on the sEMG signal ,25,27,28According to the model, the decrement of sEMG amplitude  with increasing depth within the muscle is similar to that due to the increasing thickness of subcutaneous tissue. Experimental findings from obese subjects have indicated that sEMG is still detectable with subcutaneous tissue thicknesses of 20–30 mm .Simulations of pathological fibers and MU alterations are lacking in the literature and provide an interesting research field for clinical application, the improvement of the available models, and application in the teaching and clinical interpretation of sEMG signals. A review of the use of sEMG in neuromuscular pathologies is provided by Hogrel .The only potential map that is generated on the skin by a biological signal is the monopolar map. Other maps may be obtained using analogue or numerical combinations of monopolar electrode potentials, as indicated in With respect to linear electrode arrays, bi-dimensional electrode arrays or grids provide additional information in the muscle fiber transversal direction and allows for the better discrimination between MU “signatures” and orientation, thereby facilitating the decomposition of the sEMG into the constituent MUAPs, as well as the localization of the active MUs in space and the size of the MU territory .https://www.robertomerletti.it/en/emg/material/books/ for a more complete list), which provide a comprehensive mathematical analysis of these problems. The concepts presented in this section raise a number of practical questions, such as “What should the size  of the electrodes and the IED be to allow for the correct reconstruction of a sampled image by interpolation?”, “Are there optimal values for the size and IED for maximal information extraction?”, “How big should an electrode grid be?”, “Where should it be located?”, “What are the advantages and disadvantages of monopolar versus SD images?”, and “When is a single electrode pair preferable to HDsEMG?”. These and many other issues are addressed in Electrodes that are applied to the skin are not point-like, as is often assumed in modeling. From the theoretical signal processing point of view, the full information that is contained in the superficial distribution of EMG potential can only be obtained when proper sampling in space is performed  and a large IED  introduce the attenuation of the highest harmonics in the signal , as expIn sport applications, sEMG can be used to compute the so-called localized myoelectric manifestations of muscle fatigue. Since this indicator is based on the spectral features of the signals, the filtering effect of the detection system  cannot be ignored. Users must be aware that their results depend on the electrode configuration and cannot be compared to those obtained using different electrode geometries, e.g., in the literature. The user must also be aware that the electrode size is the electrical contact area (possibly mediated by gel) and does not include the surface of the external adhesive disks that keep the electrode in place when present.An electrode has a highly conductive surface, which forces all of the points below it to have the same voltage. This voltage is approximately the mean value of the voltages at the points below the electrode surface (without the electrode). This averaging effect is a form of low-pass filtering, which reduces the “sharpness”, or high-frequency content, of the detected voltage. To understand the relevance of this effect using a simple example, consider the animation in As indicated in the literature , sEMG elAgain, it is clear that electrodes that have diameters of 5 mm are barely acceptable, while electrodes that have diameters of ≥10 mm introduce substantial filtering and modify the waveshape, amplitude, and spectral features of the MUAPs and, with that, the interferential sEMG signal, particularly in lean subjects with many MUs that are located close to the skin surface see . Neverth1, and C–D, spaced by an IED of e2, is provided as a teaching example. The results in time are very different. If e2 were equal to the wavelength of the propagating signal, the output in time would be zero at all times, thereby generating an artificial “dip” in the amplitude and power spectrum of the time signal for that particular frequency. For this reason, the IED must be smaller than half of the shortest wavelength that contributes to the sEMG signal, which is about 10 mm (corresponding to 100 cycles/m) for MUs that are close to the skin surface [The ubiquitous differential detection (SD) provides the voltage difference (versus time) between two electrodes that are spaced by an IED in the fiber direction.  surface . AccordiIn clinical practice, SD (bipolar) sEMG detection is often performed using electrodes that have diameters of 10 mm or more and an IED of 20 mm or more. The combined effect of these values has been discussed in a tutorial and a textbook . Of The above considerations apply in general and also specifically in the case of muscles that are located very close to the skin surface with thin skin and subcutaneous tissue. In the case of more distantly located muscles or subjects with a higher body mass index, these considerations may be somewhat relaxed because of the low-pass filtering effect introduced by the increased distance between the source and detection points. This factor reduces the bandwidth of the sEMG signal in space and time. This issue has been investigated by Minetto et al. , who conSimilar considerations apply to the issue of electrode size. The option to select IED implies adjustable selectivity, which is not possible with coaxial needles. The issue of electrode location, size, and IED becomes particularly important when electrode grids are used, spatial interpolation is applied or individual MUAPs are to be analyzed.The distribution of sEMG potential is a time-evolving monopolar image (a movie) whose full information content can only be recovered and used when the image is properly sampled in space and time. However, most current clinical applications are based on traditional bipolar (SD) readings since the obtained information is, in general, appropriate for answering clinical questions with an adequate compromise between the in-field feasibility of the activity detection of many muscles and the reduction in information on the active MUs.It is important to understand that a bipolar recording is nothing more than taking two samples in space out of the monopolar map and plotting their instantaneous voltage difference versus time. When using bipolar detection, some of the strict requirements concerning the electrode size and IED of an electrode grid can be somewhat relaxed in favor of a larger detection volume and lower noise, at the price of lower selectivity and a greater risk of crosstalk. Electrodes that are located improperly or have large sizes and distances cause waveform changes  and an oIn addition, during dynamic contractions, the muscle moves under the electrodes and this may cause changes in the sEMG amplitude that are only due to the changes in the relative IZ position. These issues are rarely discussed in the clinical literature or addressed in schools or courses and sEMG users seem not to be aware of them. Consequently, incorrect conclusions may be reached by unaware users.Proper skin treatment is important for both bipolar and HDsEMG recordings. In HDsEMG, the relatively large number of electrodes increases the likelihood of bad contact and requires the accurate treatment of the skin , preferably without using alcohol, which leaves skin dry . This reThe identification of the IZ by means of linear electrode arrays or HDsEMG, as reported in When the toxin is applied to the IZ, a lower dose can be highly effective ,5,42. ThThe identification of the IZ is also a useful tool for planning surgery, for example, in the case of episiotomy during child delivery. The innervation to the external anal sphincter muscle may be damaged due to episiotomy, thereby increasing the chances of future fecal incontinence . The EurDespite the literature in this field ,46,47, tA comprehensive overview of all of the clinically possible applications of single channel and HDsEMG in neurology exceeds the purpose of this paper. Therefore, only a few relevant examples are highlighted in the following section to underline the need for training with a view to future applications. For a more comprehensive analysis, refer to the systematic reviews in ,9,32.HDsEMG was already being used in the early 1990s to differentiate the pathologies of neuronal origin from those of muscular origin. Ramerkers et al.  were ablAs HDsEMG is a non-invasive method, it is particularly useful for monitoring the progress of neuromuscular disorders in children. Furthermore, for superficial muscles, HDsEMG provides additional information about the MUs and their recruitment, which is not accessible through needle EMG but could be relevant for diagnostic purposes. This includes information about the CVs of MUAPs along the muscle fibers, as well as the spatial distribution of excitation within a muscle.Many other neurological applications of HDsEMG are clinically relevant. Among these are hypokalemic periodic paralysis, pathological fatigue, and MU size estimation, presented in the reviews by Zwarts et al. , Drost eNumerous applications of HDsEMG are being developed in research labs to decode the neural drive to muscles by means of the decomposition of the sEMG into the constituent MUAP trains. These methods are based on the early work of Holobar and Zazula  and are Finally, it is fair to say that medical devices can only be used within their “intended use” (what can and cannot be carried out with that device), which is indicated by the producer in the first pages of their user manual. Any diagnostic tool requires a class II medical device certification in Europe, an FDA approval in the USA or a similar certification in other countries. Users and researcher should verify the certification level before buying or using sEMG devices for specific applications.In neurorehabilitation, the use of motion analysis with sEMG clearly influences treatment planning in multiple patient populations and can lead to better outcomes when properly used . Gait anThe main errors in the use of sEMG for the evaluation of neurological patients are attributable to the type of electrodes, the placement protocol, and the presentation of the data that are chosen. The traditionally used SENIAM recommendations for electrode placement  may not The width of the electrodes and the IED can also play a crucial role, especially when recording the activity of small muscles, such those as in children. The disposable ECG pre-gelled electrodes that are normally used in clinical evaluations are often too large. When the electrode contact area is wider than the target muscle, it can cover more than one muscle, thus reporting an incorrect activation time due to crosstalk.Finally, it is important that the reports of the examinations carried out contain raw traces to distinguish the sEMG signal from other possible artifacts  that areThe issue of proper signal representation and scaling (of the electrodes and not the output of the amplifier) may seem obvious and trivial, but it is not . Figure Surface EMG is fundamental for the proper design of workstations and chairs, the planning of sport training, and the understanding and prevention of neck, shoulder, and back pain ,75,76,77Electrodiagnosis in New Frontiers of Clinical Research [Ergonomics, occupational medicine, and sport sciences require specific competencies and training in sEMG. These areas are affected by the barriers and difficulties that have been discussed elsewhere . The earResearch , and theResearch , among mResearch .In addition, Martin and Acosta-Sojo  indicateFurther considerations for sEMG applications in sports and ergonomics are relevant and discussed in the extensive literature ,86 but eThe published literature ,20,36,87As indicated in the introduction, this work does not present innovative research results concerning sEMG hardware, processing techniques or applications. Rather, it presents (a) a number of the “first level” fundamental concepts of sEMG detection and interpretation that clinical operators should be familiar with and (b) some model-based teaching tools that could be useful to teach these concepts. All of these concepts can be found in textbooks and tutorials, in which they are presented within the mathematical framework that engineers are familiar with. This framework is unacceptable to most clinical operators, who have neither the need nor the background required to understand it. This work provides material and suggestions concerning the teaching of these concepts and their transfer into the educational curricula of clinical figures.The same applies to other “second level” technical concepts, such as the spectral analysis of sEMG, the myoelectric manifestations of muscle fatigue, image segmentation and the definition of regions of muscle activity, the decomposition of interferential EMG into the constituent MUAP trains, the association between sEMG and biomechanical variables, sEMG in dynamic conditions, etc. These concepts are not discussed in this work, which is focused mostly on the fundamental issues of sEMG detection and simple model-based interpretation and teaching.Surface EMG is very rich in information that can be extracted to draw conclusions about the coordination between muscles and muscle groups  and the A number of textbooks, recommendations, tutorials, consensus papers, and editorial projects have been published concerning these issues ,36,89,90https://isek.org/emg-standards, https://www.tudelft.nl/en/education/programmes/bachelors/kt/bachelor-of-clinical-technology/, and https://www.tudelft.nl/onderwijs/opleidingen/masters/technical-medicine/msc-technical-medicine/).A fundamental issue is the technology transfer from research labs to professional and medical schools, as well as to healthcare institutions. The simplification of concepts  and the availability of free teaching materials and recommendations are by far insufficient. As Rogers  notes, ihttps://www.tudelft.nl/en/education/programmes/bachelors/kt/bachelor-of-clinical-technology/, and https://www.tudelft.nl/onderwijs/opleidingen/masters/technical-medicine/msc-technical-medicine/) within the BS and MS curricula for courses on “advanced signal acquisition”, “sensing neurophysiological signals”, and the “electrostimulation of the neurophysiological system”. These new figures may solve the problem of the lack of time to teach measurement techniques, such as sEMG, to strictly clinical operators. This issue of the lack of time has been pointed out repeatedly in a number of surveys [As in the case of other bioelectric signals, it is up to the clinical operator to promote and use newly available technical information that is suitable for properly answering clinical questions. Learning about this in school is important; however, the fields of rehabilitation technology and neuromuscular instrumentation are becoming so extensive that it is hard to fit even the basic concepts discussed in this work into the few academic years that lead to a degree in physiotherapy, sport and movement sciences or ergonomics. To some extent, this is true in other healthcare fields as well and has justified the training of new interdisciplinary professional health figures, such as the “clinical technologist” that trains at the Technical University of Delft (NL)  using analogies and user-friendly models.The success of any future hardware/software technology to extract information from sEMG fundamentally depends on the ability of the operator to collect “good” sEMG signals from the desired muscles that are free from artifacts and power line interference and have minimal crosstalk from other muscles. The proper training and academic education of operators is a necessary condition for the success of the available, as well as future, technologies within this field.


Overall, 270 adults  aged 18 to 45 years were evaluated. Multivariable linear regression was performed to test the association between RBP4 and fecal biomarkers of impaired gut health. RBP4 concentration was positively correlated  with BMI and was significantly higher in healthy controls than undernourished adults (P < 0.001), in male than female (P < 0.001), and also in employed (P < 0.001), smokers (P = 0.048) and participants with low Self-Reporting Questionnaire (SRQ)—20 scores  (P = 0.049). Statistically significant negative correlations were observed between RBP4 and fecal biomarkers of gut enteropathy including myeloperoxidase , neopterin , and alpha-1 anti-trypsin . Multivariable linear regression analysis showed that increased RBP4 concentration was associated with a significant reduction in fecal neopterin  after adjustment for age, sex, nutritional status at enrollment, education, dietary diversity score, SRQ-20 score, improved sanitation, household animal exposure, and alpha-1-acid glycoprotein. The study findings revealed an inverse relationship of plasma RBP4 concentration with fecal biomarkers of altered gut health among slum-dwelling lean adults in Bangladesh.The relationship of retinol binding protein 4 (RBP4) with biomarkers of intestinal health and gut integrity in adults is unknown. We sought to determine the correlation between plasma RBP4 level and BMI and investigate the relationship of circulating RBP4 concentration with biomarkers of environmental enteric dysfunction among lean adults (body mass index [BMI] < 25.0 kg/m We also investigated whether elevated plasma RBP4 concentrations were associated with reduced expression of fecal biomarkers of EED.Environmental enteric dysfunction (EED), an asymptomatic small intestinal disorder, results in chronic intestinal inflammation and increased gut permeability. EED is rampant among the residents of unhygienic environments with the suboptimal provision of clean water supply and sanitation, resulting in frequent exposure to enteric pathogens.2) and healthy (BMI between 18.5 and 24.9 kg/m2) adults were defined according to the WHO criteria based on the BMI (the weight in kilograms divided by the square of the height in meters). The exclusion criteria for enrolment in the study were another family member enrolled in the same study, suffering from any severe disease requiring hospitalization, presence of congenital anomaly or chromosomal abnormalities, being pregnant or lactating woman, and presence of any known chronic illness.This study was conducted in an urban settlement in Dhaka, Bangladesh. Overall, 270 adults  aged between 18 and 45 years were enrolled from October 2018 to January 2019. Undernourished . Informed written consent was obtained from all the participants enrolled in the study.Sociodemographic information including dietary data in the food frequency questionnaire (FFQ) and self-reporting questionnaire (SRQ-20) data were collected at the time of enrollment. FFQ is a dietary assessment tool used to identify the types and estimate the frequency of food items and beverages consumed by an individual over a specified period. SRQ-20 is an instrument used to screen mental health disorders and detect psychological symptoms in adults.g for 10 minutes within 2 hours of collection. Stool samples were collected and preserved in a liquid nitrogen tank within 20 minutes of production. No additive or preservative was added to the fecal samples. All the samples were stored at –80°C, until analysis.Two milliliters of blood samples were collected aseptically into blood collection tubes  by venipuncture from all the participants. To separate the plasma, blood samples were centrifuged at 4,000 × Helicobacter pylori fecal antigen test was also performed using Amplified IDEIA Hp StAR .Laboratory assays were performed in the parasitology laboratory at icddr,b in Dhaka, Bangladesh. The biomarkers were tested in a single batch to minimize potential intra- and interbatch variations. Plasma RBP4  and blood biomarkers such as C-reactive protein , alpha 1-acid glycoprotein (AGP) , low-density lipoprotein receptor-related protein 1  and Ferritin  were estimated using commercial ELISA kits following the instructions provided by the manufacturers. Hemoglobin status was determined using Hb 201 microcuvette of HemoCue Company. Plasma zinc was measured by the atomic absorption spectrometry method. Stool biomarkers were measured through ELISA according to the standard protocols given by the manufacturers. Stool samples were analyzed for MPO , NEO , and AAT . H. pylori infection); plasma LRP1; plasma RBP4; and anthropometric variable (BMI). Dietary diversity score and SRQ-20 score were categorized based on previously published literature.–The following variables were included in the study: demographic ; socioeconomic ; water, sanitation, and hygiene practices ; personal ; dietary ; markers of systemic inflammation ; biochemical ; fecal biomarkers of altered gut health ; enteric infection . However, we did not exclude any variables for multicollinearity as VIF values were found to be < 4.0 in all the regression models. A two-tailed P value < 0.05 was considered statistically significant. All the analyses were performed using R version 3.5.3  software.Results are expressed as mean (± SD) for normally distributed continuous variables and median with interquartile range (IQR) for asymmetric numeric variables. A proportion estimate was used to summarize the categorical variables. Nonparametric Mann–Whitney test was performed to examine the differences in RBP4 levels between the comparison groups. Spearman’s correlation coefficient (rho) was calculated to analyze the correlations of RBP4 with fecal biomarkers of altered gut health, inflammatory biomarkers, and plasma micronutrient levels of the participants. Multivariable linear regression was performed to test the association between RBP4 and fecal biomarkers of altered intestinal health after controlling for the potential confounders. We constructed three independent linear regression models considering RBP4 as the explanatory variable and MPO, NEO, and AAT as the outcome variables, respectively. Variables with skewed distribution  were log-transformed before regression analyses. Covariates were included in each multivariable model if the A total of 270 participants with a mean (± SD) age of 24.2 (± 6.6) years were enrolled in this study. Of them, 95 (35.2%) were used, and 24 (8.9%) were smokers. The sample comprised 205 (75.9%) females, with 110 (53.7%) assigned to the undernourished group and 95 (46.3%) to the healthy group. The mean (± SD) BMI of the participants was 19.6 (± 2.6). The median value with IQR of hemoglobin was 12.8 (11.7–13.8) gm/dL, ferritin was 50.6 (22.2–99.7) ng/mL, and plasma zinc was 0.73 (0.66–0.82) mg/L. The distribution of sociodemographic, biochemical, and outcome characteristics of the participants are shown in P < 0.001). We also observed that RBP4 concentration was higher  in the healthy controls than in the undernourished adults  and the difference was statistically significant (P < 0.001).P < 0.001). RBP4 levels were increased in employed (P < 0.001), smokers (P = 0.048), and participants with low SRQ-20 scores (P = 0.049). There were no significant differences in plasma RBP4 concentration between the groups based on education, dietary diversity score, substance abuse, and H. pylori infection.P < 0.001), neopterin , and alpha-1 anti-trypsin . RBP4 was positively correlated with ferritin , hemoglobin  and LRP1  concentrations measured in plasma. A significant positive correlation was also observed between RBP4 and CRP  in adults enrolled in this study.P < 0.001) after adjustment for age, sex, nutritional status at enrollment, education, dietary diversity score, SRQ-20 score, improved sanitation, household animal exposure, and AGP as confounders. However, the relationship of circulating RBP4 with fecal MPO and AAT did not demonstrate any statistically significant relationship in multivariable linear regression analyses.In this study involving 270 young adults, we observed that plasma RBP4 concentration was significantly lower in underweight adults than in the healthy controls, and BMI was positively correlated with RBP4 levels in the bloodstream. The fecal biomarker values measured in the stool samples were higher in undernourished participants than in healthy adults and exhibited negative correlations with RBP4. The study findings also demonstrated a significant inverse relationship between RBP4 and fecal biomarker of intestinal inflammation. Because of the lack of evidence on the relationship between biomarkers of EED and adipokines, the findings from this study will provide further insights to understand the complex mechanism of EED in young adults.––,,Our finding on the positive correlation between RBP4 and BMI is consistent with previous studies done on adult participants.–,,–The average fecal biomarker values were markedly raised in our study participants against nontropical normal values .–,Evidence suggests that the rise of positive acute-phase proteins with a simultaneous decrease in negative acute phase proteins or visceral proteins indicate the presence of inflammatory process within the body.Our study has several strengths and also potential shortcomings. To the best of our knowledge, this is the first study to demonstrate the relationship between plasma RBP4 concentration and biomarkers of EED in adults living in low-income settings. The use of multiple measures of EED is a strength of this analysis. We used multiple procedures to ensure compliance and reliability of data, sample, and analysis according to standard operating protocols. Additionally, several possible confounding variables were taken into consideration in this analysis that are possible risk factors for altered gut health in adults, including age, sex, education, occupation, income, dietary diversity, water, sanitation and hygiene practice, and smoking history. Limitations of our study include a lack of data regarding body fat percentage, lipid variables, fasting blood glucose, physical activity, transthyretin, insulin concentration, blood pressure, and dietary intakes of short chain fatty acids and triglycerides. These variables should be adjusted to determine the precise relationship between RBP4 and biomarkers of altered gut health. Moreover, RBP4 concentration in plasma depends on the vitamin A status of an individual.In conclusion, RBP4 was positively correlated with the BMI of slum-dwelling lean adults in Bangladesh. Our findings also revealed the inverse relationship of plasma RBP4 levels with fecal biomarkers of altered gut health, suggesting that biological mechanisms influencing RPB4 concentration may be related to the impairment of gut function. Further research, including well-designed longitudinal studies considering larger sample sizes and all possible confounders, is needed to confirm the potential effects of RBP4 on intestinal health and clarify the role of impaired vitamin A metabolism in the pathogenesis of altered gut function as well as EED in malnourished adults living in resource-poor settings.


Colorimetric reagent dipstick (CRD) for leukocyte esterase (LE) has shown potential for diagnosing and ruling out bacterial meningitis. Potential advantages over traditional cerebrospinal fluid (CSF) analysis include the small quantity of CSF required, rapid results, and easy interpretation. Our study aimed to determine whether clinicians in LMICs could accurately diagnose bacterial meningitis using CRD at the bedside.A convenience sample of 143 patients requiring lumbar puncture for possible meningitis were enrolled from 1 October 2018 to 31 December 2019 at three hospitals, one each in rural Burundi, the Democratic Republic of Congo, and Kenya. CSF was analyzed using CRD followed by traditional laboratory-based analysis by technicians blinded to bedside results. Results were analyzed for concordance rates, sensitivity/specificity, positive and negative predictive values and impact on clinical decision-making.One hundred and one patients were included in the analysis. The prevalence of bacterial meningitis in the convenience sample was 35% (35/101) as defined by microscopy or positive Gram stain. Using a threshold of “any positivity” for LE on the CRD, bedside testing correctly identified 33/35 cases (sensitivity 94.3%) and had a NPV of 92%. When only a clearly positive (≥ “+” for LE) CRD criterion was used, sensitivity and NPV were 77.1% and 86.2%, respectively.Despite considerable promise, in our study, color reagent dipstick analysis of CSF did not perform well enough to rule out meningitis or screen samples for the need for microscopy. The development of a CSF-specific dipstick should be considered. In settings where neuroimaging prior to lumbar puncture (LP) is unavailable, unreliable, or prohibitively expensive, CRD testing mitigates the risk of herniation and reduces LP-associated morbidity as it requires only 0.1 mL of CSF to perform Our study aimed to determine whether clinicians in LMIC could accurately rule out bacterial meningitis or screen which CSF samples to send for microscopy using CRD at the bedside.This was a prospective case series study carried out simultaneously at three rural hospitals in Burundi, the Democratic Republic of Congo, and Kenya. Inclusion criteria were fever plus headache, seizure, coma / altered mental status, nuchal rigidity or meningeal sign such as Kernig's or Brudzinski's. Exclusion criteria were medical contraindication to lumbar puncture , inability to obtain consent, and/or risk of harm due to delay to antibiotics >1 hr necessary to perform LP though this last criterion did not exclude any patients due to frequent pre-treatment with antibiotics prior to transfer. CSF was obtained by usual technique and then subjected to bedside analysis using CRD . Results were interpreted at bedside by the clinician performing the LP. Laboratory technicians, blinded to the dipstick results, then performed standard microscopy evaluation and, where available, biochemistry assays on the CSF sample.Kibuye Hope Hospital and Nyankunde Hospital are district referral and teaching hospitals located in rural Burundi and eastern Democratic Republic of Congo, respectively. Cell count, Gram stain, and biochemical assays are usually available at Nyankunde whereas Kibuye routinely lacks the ability to do biochemical analysis. Kijabe Hospital is a WHO level 5 tertiary care and academic hospital located in rural Kenya where microscopy and biochemical analysis of CSF are routinely available.The Biomedical Ethics Committee of the University of Burundi Medical Center approved this study protocol overall and the respective hospital Institutional Review Boards approved and oversaw local patient enrollment and data collection.Each hospital enrolled patients during a 12 month period. Once the enrollment period ended (30 Sep 2019 for Kibuye and 31 December 2019 for Kijabe and Nyankunde), data were reported to the principal investigator and analyzed for concordance rates, sensitivity and specificity, positive and negative predictive values, and impact on clinical decision-making. The concordance rate for CRD heme and RBCs on microscopy was used as an internal control for test reliability. A positive case of meningitis was defined by gold standard microscopy of ≥10 nucleated cells/uL CSF or bacteria seen on Gram stain. Interpreters of CRD then completed a 30 question evaluation tool to ascertain ordinal inter-rater reliability which was then calculated as Krippendorff's alpha. The authors considered a priori that a 1% miss rate would be counterbalanced by the benefits of more rapid diagnosis in more proximate settings in addition to more judicious antibiotic stewardship for negative cases.The Netherlands Initiative for Capacity-development in Higher Education (NICHE) provided partial grant support for this study.Between 1 October 2018 and 31 December 2019 a convenience sample of 143 patients . Using “any positivity” for leukocyte esterase on the CRD, bedside testing correctly identified 33/35 cases (sensitivity 94.3%) and had a NPV of 92%. . Using oThe difference in total number of samples evaluated for heme/RBCs and LE/WBCs is due to missing RBC# for some samples. Inter-rater reliability on standardized instrument via Krippendorff's alpha was 0.915.We do not consider a 6% miss rate or an NPV of 92% as acceptable for a screening test with such a morbid disease as bacterial meningitis. While the prevalence of meningitis in our sample was substantially greater than the assumed 10% made in the recent meta-analysis, The fact that the concordance rate for heme and RBCs was worse than for our Inclusive Criterion of leukocyte esterase suggests that the performance of the dipsticks may be partially responsible for the observed discordance. This presents an important avenue for improving technical performance of CSF evaluation by CRD. Per the manufacturer, the discriminatory range for leukocyturia on the dipsticks is 0 to 500 (+++) WBC/uL in five graduated steps with “+/-“ representing 15 WBC/uL. One can envision a dipstick tuned for CSF with a narrower discriminatory range but a greater color change reaction as the diagnostic importance of distinguishing between 70, 125, and 500 WBC/uL is minimal with CSF pleocytosis in a test meant to screen patients for meningitis or triage which samples require microscopic analysis.Our calculated measure of inter-rater reliability, Krippendorff's alpha, was good at 0.915 with ≥0.8 generally considered to be reliable Our study had several limitations. Our sample size was small compared to the overall incidence of meningitis in these resource-constrained settings. Like previous studies, we focused solely on bacterial meningitis to the neglect of viral and tuberculosis meningitides. At a systems level, staff turnover and disruptions due to local violence and instability led to some patients that would have met inclusion criteria to not receive an assessment. Additionally, 13 (10%) of our samples were disqualified due to failure of one batch of dipsticks to pass quality assurance evaluations during the collection window. It is not clear that inclusion of these samples in the analysis would have changed the test performance parameters significantly, but it is a non-trivial failure in the broader application of such a screening protocol. Lastly, there were missing data variables for some of the patients which can cause unintended bias. Imputing negative or normal values for missing data, however, did not significantly change the results.There were several strengths to our study. The inclusion of patients of all ages provides good generalisability to the populations affected by bacterial meningitis. Conducting this study across multiple rural sites, each with variable resource constraints, also aids in improving generalisability as the majority of patients in our three countries, and many others in Africa, receive care in similar settings.Bedside evaluation of CSF for pleocytosis using a color reagent dipstick represents an attractive tool in diagnosing bacterial meningitis in resource-limited settings with advantages in speed, ease and reliability of interpretation, and reduced morbidity of LP due to the small volume of CSF needed for analysis. However, CRD did not perform well enough in clinical practice as a rule-out test or a means of screening samples prior to traditional analysis to obviate the need for microscopy. A CSF-specific dipstick may be able to resolve the remaining challenges to adopting such a strategy in low- and middle-income countries.An infographic of this study's results in English and French was shared via WhatsApp with the staff of the respective hospitals. The abstract was also made into a poster for presentation at the Kijabe Hospital Research Forum on 11 Mar 2022.Authors contributed as follow to the conception or design of the work; the acquisition, analysis, or interpretation of data for the work; and drafting the work or revising it critically for important intellectual content: CBW contributed 30%, LM & PL contributed 10% each, TR & EK contributed 15% each, BJB contributed 20%. All authors approved the version to be published and agreed to be accountable for all aspects of the work.The authors declared no conflicts of interest.


Circulating cell-free DNA (cfDNA) analysis has the potential to revolutionise the care of patients with cancer and is already moving towards standard of care in some adult malignancies. Evidence for the utility of cfDNA analysis in paediatric cancer patients is also accumulating. In this review we discuss the limitations of blood-based assays in patients with brain tumours and describe the evidence supporting cerebrospinal fluid (CSF) cfDNA analysis. We make recommendations for CSF cfDNA processing to aid the standardisation and technical validation of future assays. We discuss the considerations for interpretation of cfDNA analysis and highlight promising future directions. Overall, cfDNA profiling shows great potential as an adjunct to the analysis of biopsy tissue in paediatric cancer patients, with the potential to provide a genetic molecular profile of the tumour when tissue biopsy is not feasible. However, to fully realise the potential of cfDNA analysis for children with brain tumours larger prospective studies incorporating serial CSF sampling are required. Circulating cell-free DNA (cfDNA) is fragmented genomic DNA that is present in biological fluids. In patients with cancer, a subset of cfDNA is derived from tumour cells and hence is known as circulating tumour DNA (ctDNA). In this review the term ctDNA is used to refer to tumour-derived DNA present in any accessible body fluid, and the term CSF-ctDNA for tumour derived DNA specifically from CSF. When discussing analytical methods, the term cfDNA is more appropriate, as we do not have the tools to separate the ctDNA from cfDNA in the laboratory.The isolation and molecular profiling of cfDNA has shown great potential for identification of actionable biomarkers in various cancers, especially genomic molecular profiling identifying single nucleotide and copy number changes. Given the inherent difficulties of acquiring tissue biopsies in children with cancer, this less invasive method offers not only the possibility of providing the molecular profile of the tumour when tissue biopsy is not possible but also the potential to assess tumour heterogeneity and monitor disease course and response to treatment through serial sample collection. The evidence for the clinical utility of cfDNA analysis in patients with different types of paediatric tumours has been accumulating, with highest potential in neuroblastoma, osteosarcoma, rhabdomyosarcoma, malignant renal tumours and Ewing’s sarcoma –4. HowevThe need for liquid biopsies is very high in patients with central nervous system (CNS) tumours. The ability of neuroimaging to discriminate different brain tumour diagnoses is low, and current practice, as per World Health Organisation (WHO) criteria mandates both histopathological classification and advanced molecular characterisation, which is now considered standard of care . For cerThe potential genetic, epigenetic and protein expression biomarkers that can be evaluated in different paediatric brain tumour types using liquid biopsy tools on circulating tumour cells, miRNA and extracellular vesicles have been reviewed elsewhere , 12. In In this review we will discuss the challenges of cfDNA analysis from the blood in patients with CNS tumours and highlight the potential to use CSF as alternative source of cfDNA in these patients. We will discuss the practical considerations of sample collection, processing and analysis and suggest recommendations based on current practice and knowledge, towards the standardisation of these assays in future studies. As larger scale studies will enable the clinical integration of these assays for variant detection, we will also discuss potential future applications, such as the potential to monitor disease course and to evaluate spatial and temporal heterogeneity, with emphasis on CNS tumours.In most cancers, blood is a good source of circulating tumour DNA and can be used to obtain a molecular profile of the tumour in a minimally invasive way. However, in patients with CNS tumours the ability to detect ctDNA in the blood is much more limited compared to other solid tumours , 17. In The limited sensitivity of blood-based assays is mainly thought to be due to the blood brain barrier (BBB) that restricts the shedding of ctDNA into the bloodstream. This idea is supported by relatively higher ctDNA levels in high grade glioma (HGG), which is characterised by disrupted BBB and meningioma which grows outside of BBB , 19. ForCertain CNS tumour types, such as medulloblastoma or ependymoma, can sometimes metastasise outside of the CNS. In these cases, blood based cfDNA profiling may be useful, even before the metastasis occurs, as shown by the presence of circulating tumour cells (CTCs) and ctDNA in several therapy-naïve paediatric medulloblastoma patients . HoweverOverall, while some neurological tumours are potentially more detectable by liquid biopsy than others, detection of ctDNA with clinically informative variants in the blood is inconsistent in patients with CNS tumours.Several ways to improve the ctDNA detection from the blood of patients with brain tumours have been explored. For example, pre-amplification of cfDNA after extraction has been described as a way to improve the detection of low level ctDNA variants. This led to the detection of ctDNA in 80% of newly-diagnosed patients with glioma from 1 ml of plasma and in 87% of patients from 0.5 ml of cerebrospinal fluid (CSF) . In a diIn-vivo and patient studies have both shown that higher ctDNA levels are present after radiotherapy  than from plasma in a range of CNS tumours, such as HGG and medulloblastomas , 28–33. In the paediatric cancer literature, evidence is accumulating that profiling of CSF-cfDNA could be a feasible and efficient tool for the diagnosis and monitoring of paediatric diffuse midline gliomas and medulloblastomas , 34. ImpIn paediatric medulloblastoma, the largest study so far  demonstrated the clinical utility of copy number variant (CNV) detection though low coverage WGS (lcWGS) on CSF-cfDNA and described it as a minimal residual disease (MRD) surrogate marker . The detThe potential to use CSF-cfDNA to identify the more aggressive subclones driving disease progression has been shown by cases where CSF-cfDNA at baseline was more concordant with the relapsed tumour than with the corresponding primary tumour . In addiDespite encouraging signs of utility, it is important to acknowledge that CSF is not as easily obtainable as blood and sample processing is far from standardised. Inconsistent collection and suboptimal processing can lead to poor sample quality. For example, a recent study of paediatric medulloblastoma that failed to detect most of the mutations in CSF-cfDNA that were expected from the tissue sequencing showed that only 15/58 samples had detectable CSF-ctDNA  . The abiAs discussed above, for the majority of patients with CNS tumours, CSF is a better source of ctDNA than blood. However, obtaining CSF samples is more invasive and demanding than collecting peripheral blood, requiring sedation/anaesthesia, and increasing risk of infection when intraventricular devices are used. The majority of studies to date have relied on sampling at timepoints compatible with existing clinical practice and collected surplus CSF when routine lumbar punctures (LPs) were performed , 35. MorSuccess of molecular profiling of cfDNA depends upon maintaining cfDNA integrity and minimising the contamination from genomic DNA from non-cancer cells. Rigorous studies exploring the pre-analytical conditions needed for CSF sample processing for liquid biopsies are lacking, mainly due to the difficulty of acquiring CSF samples from patients. Therefore, the best practices must be inferred from studies in blood and the limited studies we have in CSF. The current best practices of pre-analytical CSF-cfDNA handling, based on the methodologies in the most recent literature , 38–40, •Separate supernatant from the cell pellet •Store at −80°C prior to processing; multiple freeze-thaw cycles should be avoided•Extraction methods have not been systematically evaluated, most commonly used – Qiagen® “QIAamp Circulating Nucleic Acid Kit”•Quality Control to assess DNA concentration (Qubit® assay or qPCR-based measurement) and fragment size (by automated electrophoresis systems) to confirm the presence of cfDNAIf immediate processing is not possible, collection tubes with preservative should be used.Sample needs to be processed immediately:Even though CSF has low cellular content, the separation of CSF into the supernatant and the cell pellet is necessary. The cfDNA in the supernatant of CSF has been shown to have higher VAF of cancer-associated variants when compared to the pellet from the same sample, indicating that supernatant often contains sufficient DNA and provides more reliable results than the cellular fraction , 41. It To minimise the contamination from lysing non-cancer cells when samples cannot be processed immediately, specialist cell-stabilising preservation tubes have been used for blood collection for liquid biopsies. There is a range of tubes on the market, but none are specifically designed for CSF. The only study to date comparing different conservation tubes for CSF samples suffered from the limitations of sample availability showed that Norgen® tubes with phosphate-buffered saline to top up low volume samples had the highest cfDNA yields of the different tubes tested .Whatever the source of cfDNA – blood, CSF or urine – the greater the depth of error-corrected sequencing, the more information about frequency of variants will be retained, up to the point where the number of DNA molecules present in the sample becomes a limiting factor. cfDNA tumour fraction estimates could serve as a guide to the interpretation of plasma cfDNA results, especially negative results, and inform clinical decision making . The abiDepending on the clinical situation, it is likely that cfDNA analysis will be performed without a time-matched tissue sample. It is well-documented in adult cancers that white blood cells also acquire mutations that could mistakenly be profiled as coming from the tumour tissue in blood derived cfDNA analysis . The accThese complicating factors must all be considered when translating a cfDNA assay to the clinical diagnostic setting. Accreditation and regulatory organisations like the FDA in the US, the MHRA in the UK and the EMA in Europe will require standardisation of sampling and robust clinical validation which is likely to limit the number of laboratories offering cfDNA sequencing as a clinical assay. Commercial providers are already offering CE-marked and CLIA-approved tests for extracranial ctDNA blood testing. These assays are beginning to make the transition from clinical trials into standard of care testing, either through send-away testing or through large regional accredited laboratories like the Genomic Laboratory Hubs in England. To date, however, none offer a CSF-cfDNA focussed method to detect variants, and importantly, to report the absence of, neurological tumours. The commercial market for paediatric tumour testing is also limited, so focussed tests are likely to continue to depend upon translation of academic research assays in this specific field of diagnostics.A major potential application for liquid biopsy is the ability to detect tumour heterogeneity . Given tStudies in adult malignancies, comparing multi-region and/or multi-lesion tissue sequencing with time matched cfDNA indicate that cfDNA is representative of the diversity of intra-tumoural and intra-lesional heterogeneity , 59. HowLiquid biopsies also have potential for use as a non-invasive means of assessing treatment response and for surveillance for disease relapse. Dynamics of mutation variant allele frequency and/or genome wide copy number profiles in cfDNA are reported to mirror disease progress in diffuse midline glioma and medulloblastoma –16. ThisEven when pre-analytical challenges are addressed, biological limitations remain - low ctDNA amounts in the blood or CSF and relatively low volumes of CSF collected from paediatric patients limits sensitivity and specificity. This review focuses on the most established cfDNA readouts – SNV and CNV profiling. However, an inherent limitation of the sequencing approaches discussed above is low mutational burden in some paediatric CNS tumours which limits the number of alterations to assess and hence the sensitivity of the assays. Other forms of molecular analysis such as epigenetic, metabolomic and transcriptomic profiling have also been performed in cfDNA from patients with brain tumours , 12. EpiAn attractive alternative to standard sequence-by-synthesis techniques and ddPCR methods for cfDNA profiling is nanopore sequencing. While normally applied as long read technology, Nanopore sequencing can be applied to the short cfDNA fragments rapidly and with lower input, as it depends on the concentration of oligonucleotide ends , 85. A pAdditionally, cfRNA analysis has recently been applied for cancer detection and profiling of cancer patients  and may cfDNA analysis can contribute to molecular profiling at cancer diagnosis and relapse. It can aid diagnostic sub-classification and the assignment of risk, prognosis and allocation of targeted therapy in paediatric cancer patients. Due to the anatomic location of the tumours, blood based cfDNA profiling is challenging in patients with CNS tumours and CSF-cfDNA is emerging as a biomarker worthy of further evaluation for molecular profiling, especially in specific tumour types such as medulloblastomas or paediatric high-grade gliomas, in patients with unresectable tumours (such as diffuse midline gliomas), or where repeated tissue biopsies are required.However, to realise this potential for clinical benefit in children with CNS tumours, CSF-cfDNA tests must be robustly evaluated. Firstly, standardisation of sample processing is needed. Subsequently for each methodology, robust QC measures, normal ranges and diagnostic cut-offs must be defined. This will require larger scale studies comparing the different methodologies for different indications. Standardisation of methodologies across international consortia will be crucial with large-scale implementation and harmonisation best placed within the context of international disease-specific clinical trials. Initiatives like this are already underway, such as the SIOP High Risk Medulloblastoma  and SIOPAs the weight of evidence for the technical utility of liquid biopsy assays increases, we must next address where the greatest potential is for added benefit in patients. It is clear for example, that the use of CSF-cfDNA profiling to aid inclusion into clinical trials when biopsy is not feasible is beneficial in the proportion of patients where cfDNA profiling is informative. In terms of disease monitoring, we still need more information to understand how much earlier and with what confidence we can detect emerging relapse in cfDNA when compared to MRI. One advantage of earlier diagnosis of relapse, before a child presents with clinical symptoms is the increased likelihood for eligibility for clinical trials. However, one could also argue that if no alternative therapies are available, earlier diagnosis of relapse may increase harm rather than adding benefit.It will be challenging to change treatment based on a non-imaging finding, which is not accommodated in current clinical trial designs. At present, inclusion criteria and response assessment endpoints are imaging based, and LPs (for CSF-cfDNA collection) are generally not mandated on clinical trials. However, as clinical trials ) are starting to collect CSF at the time of the initial biopsy and after surgery this offers the potential for further validation of these assays, and the opportunity to drive a paradigm change in clinical trial design.In conclusion, cfDNA analyses, in particular CSF-cfDNA profiling, show great potential for diagnostic and monitoring application, but comprehensive evaluation of these methodologies in ongoing clinical trials is urgently required to maximise the potential for clinical utility of cfDNA assays for children with CNS tumours.


Testicular torsion (TT) is a common urological emergency posing serious health problem in children. Prompt diagnosis and treatment of TT are very important for children to protect the affected testis. The aim of this study was to evaluate the historical features, physical examination findings, laboratory tests, and ultrasound examinations in children with TT, as well as to identify the predictors of testicular salvage in children.We conducted a retrospective record of clinical findings, laboratory data, ultrasound findings, operating results, and the results of follow-up in hospitalized children with TT from November 2004 to December 2021. A multivariable logistic regression model was used to identify predictors of testicular salvage.A total 102 hospitalized children who presented with TT were included. Patients were aged from 1 month to 16 years, with a median age of 7.71 years. TT is significantly more common in the winter. Of these patients, 77 torsions were left-sided, 24 were on the right side, and only 1 was on bilateral sides. Meanwhile, we detected that 88 children suffering from TT had intravaginal torsion of the spermatic cord, and the rest were outside. Anticlockwise torsion was found in 65 cases (63.73%) and clockwise torsion in 37 (36.27%). As a result, 60 underwent orchidectomy, while 42 had a scrotal exploration with fixation of the testis. Multivariate analysis showed that cause of TT, time to intervention, white blood cell (WBC), and mean platelet volume (MPV) were correlated with the risk of a surgical outcome.Only a small proportion of TT children received timely surgical management. Testicular salvage can be predicted by cause of TT, time to intervention, WBC, and MPV. Early scrotal exploration based on careful physical examination decreases the risk of misdiagnosis of spermatic cord torsion. A certain percentage of children with TT presenting with scrotal trauma or epididymo-orchitis should have their testicles checked to make sure that they do not have torsion, especially those who visit in the cold season. Testicular torsion (TT) is one of the most common diseases encountered in a pediatric hospital emergency department, with its incidence rate being about 1 in 4,000 males under the age of 25 , 4. It iChildren who are diagnosed with TT usually have a loss of the cremasteric reflex on the affected side and abnormal testicle direction. The most common sign and symptom of torsion is sudden onset, severe, and unrelenting scrotal or/and inguinal pain . Some chThe aim of this retrospective study is to summarize the clinical manifestations, physical examinations, auxiliary examinations, and surgical outcomes of TT in order to improve the diagnosis and treatment, as well as to explore the risk factors for predicting the outcomes of pediatric patients diagnosed with TT at the children's hospital in China from November 2004 to December 2021.Consent was not required from the Ethics Committee because of the retrospective nature of this study. Written informed consent was routinely obtained from each surgical patient or the legal guardian/next of kin for minors.A retrospective analysis of the medical records on TT from November 2004 to December 2021 was conducted at our institution. Only cases confirmed by scrotal exploration were consecutively included in this study. Patients whose parents refused surgical exploration were excluded from this study in addition to negative scrotal exploration, neonatal torsion, or testicular appendix torsion. We extracted clinical data including age, duration of symptoms onset, birth weight, gestational age of mother, mode of delivery, feeding pattern, concomitant diagnose, ultrasound characteristics, laboratory testing, and direction and degree of spermatic cord twisting. Meanwhile, some children also had other concomitant diagnoses, namely, contained hydrocele, cryptorchidism, inguinal hernia, or testicular microlithiasis. Children diagnosed with TT underwent orchiectomy and/or surgical detorsion. The contralateral testis was routinely fixed in the same fashion unless parents refused to testicular fixation.The patients were followed up at 1, 3, and 6 months postoperatively, and then examined once a year in the clinic. In addition, color Doppler ultrasound was widely used as a helpful tool for follow-up visits. We collected the number of testicular atrophies based on ultrasound after orchiopexy .First, the scrotal skin and tunica vaginalis of the affected side were incised under general anesthesia. Second, a small incision was made in the tunica albuginea to check the blood supply, and then the affected testis was covered with a piece of moistened gauze with warm saline for 10–30 min. Third, after a moment, the affected testis was rechecked for potential salvageability. Generally, orchidopexy was performed if the testicular blood flow was restored. Otherwise, the nonviable testis was removed, and then fixation of contralateral testis was performed. In practice, an in-depth communication with parents was made to decide which kind of surgery (orchidopexy or orchiectomy) is suitable for their children in the face of coagulative necrosis of the testicular parenchyma. In Meanwhile, parents also decided whether to fix the contralateral testis.t test was used. For non-normal data distribution, the Kruskal–Wallis test was applied instead. Comparisons were conducted by χ2 test or Fisher's exact test for dichotomous outcomes and unordered multiple outcomes, and by Kruskal–Wallis test for ordered multiple outcomes. A P-value less than 0.05 was considered statistically significant.SPSS version 19.0  was applied for statistical analysis. Categorical variables were presented as ratios (%) and continuous variables were presented by mean ± standard deviation (SD). All continuous variables were tested for normality using the Shapiro–Wilk test. For normal distributed data, Student's A retrospective record of 102 patients who were diagnosed with TT to our institution was made after surgery from November 2004 to December 2021. The primary characteristics of the patients are presented in These boys underwent surgery promptly after hospitalization. The common complications included bleeding and scrotal edema after operation. No serious complication was detected. Operative findings and surgical outcomes in patients with TT are shown in P = 0.002) and shorter duration of symptoms (P = 0.001) when compared to their viable counterparts (P = 0.003). There was no statistical difference in other variables between the two groups (P > 0.05).To determine the factors influencing the surgical procedures, patients were classified into two groups depending on whether they underwent orchidopexy or orchiectomy. On univariable analysis, we found that those in the orchidopexy group tended to have significantly lower degrees of twisting (terparts . In addiThere were significant differences between orchidopexy and orchiectomy in terms of white blood cell (WBC) and mean platelet volume (MPV). However, there was no statistically significant difference in other hematologic parameters between the two groups . LikewisTT is a surgical emergency and may affect testicular function and male fertility if not treated timely. Approximately 30% children with acute scrotum had delayed surgical management of TT because they were not first treated in a tertiary hospital. Patients transferred from primary and secondary healthcare units were more likely to delay management owing to the lack of experience on the identification and diagnosis of TT. Thus, it is important to continuously promote public awareness of TT, and improve pediatrician ability of diagnosis and therapy of TT from primary and secondary healthcare units.Acute severe scrotal pain is a symptom that can be identified in clinical presentation. Other common signs and symptoms of torsion, as well as other causes of acute pediatric scrotum syndrome, include sudden abdominal or inguinal pain, nausea, and vomiting. Not all TT cases have acute severe scrotal pain. Actually, we often need to make an accurate differential diagnosis of an undescended TT from acute abdomen or incarcerated hernia through proper abdominal and inguinal examination, especially for defective children or infants. It may be difficult to distinguish from other causes of acute pediatric scrotum syndrome such as epididymo-orchitis, infected hydrocele, and torsion of the appendix of testis. Surgery is the primary treatment after suspicion of TT. The duration of pain or symptom was a critical factor of surgical selection . HoweverPrevious studies have always have explored the risk factors of TT and found that age is an important risk factor. TT can occur at any age but usually occurs in young males, especially in the first year of life and around puberty , 14. ChiDebate always exists regarding contralateral testicle fixation, arguing that the low risk of contralateral torsion outweighs the risk of complications from orchidopexy . The exaThough we collected the medical records of TT cases from the past decade, some limitations still existed. First, our study design was a retrospective study and restricted the accuracy of results. Second, only patients with TT in our pediatric center were included, which could not completely represent the general condition. Finally, some potential or undiscovered factors may affect the ultimate results, such as family history of TT, medical insurance, and guardians’ work. Therefore, a prospective, well-designed, and large-scale study should be performed.Only a small proportion of TT children received timely surgical management. Testicular salvage can be predicted by cause of TT, time to intervention, WBC, and MPV. Early scrotal exploration based on careful physical examination decreases the risk of misdiagnosis of spermatic cord torsion. A certain percentage of children with TT presenting with scrotal trauma or epididymo-orchitis should have their testicles checked to make sure that they do not have torsion, especially those who visit the in cold season.


Kidney transplantation is the therapy of choice for people living with kidney failure who are suitable for surgery. However, the disparity between supply versus demand for organs means many either die or are removed from the waiting-list before receiving a kidney allograft. Reducing unnecessary discard of deceased donor kidneys is important to maximize utilization of a scarce and valuable resource but requires nuanced decision-making. Accepting kidneys from deceased donors with heterogenous characteristics for waitlisted kidney transplant candidates, often in the context of time-pressured decision-making, requires an understanding of the association between donor characteristics and kidney transplant outcomes. Deceased donor clinical factors can impact patient and/or kidney allograft survival but risk-versus-benefit deliberation must be balanced against the morbidity and mortality associated with remaining on the waiting-list. In this article, the association between deceased kidney donor characteristics and post kidney transplant outcomes for the recipient are reviewed. While translating this evidence to individual kidney transplant candidates is a challenge, emerging strategies to improve this process will be discussed. Fundamentally, tools and guidelines to inform decision-making when considering deceased donor kidney offers will be valuable to both professionals and patients. Kidney transplantation is the treatment modality of choice for kidney failure patients deemed fit enough for surgery. While successful kidney transplantation lowers both cardiovascular  and all-p < 0.001), then utilization of discarded kidneys  could generate 132,445 allograft life-years  cause of death is cerebrovascular accident, 2) pre-existing history of systemic hypertension, and 3) terminal serum creatinine >1.5 mg/dl. The criteria for defining ECD was based on the presence of variables that historically increased the risk for graft failure by 70% compared with a standard criteria donor (SCD) kidney .Previous systematic reviews suggested ECD kidneys should not be offered to younger (aged <40 years) kidney transplant candidates or those undergoing re-transplantation . ECD kidHowever, recent analyses support broadening access with careful risk stratification. Querard et al. conducted a systematic review and meta-analysis of 32 studies comparing survival outcomes between SCD and ECD kidneys . Pooled p < 0.001) and CIT <12 h (p = 0.030) according to a French study (p < 0.0001) increased risk for graft failure using ECD versus SCD kidneys was observed in one study, population-average effect using propensity scores with 10-year follow-up highlighted a minimal absolute effect of only 8 months (95% CI 2–14 months) quicker time to graft failure attributed to ECD kidneys  but in whom cardiac standstill or cessation of cardiac function occurred before organs were procured, with cessation of cardiac function initiated deliberately (controlled) or occurring spontaneously (uncontrolled) .n = 739) or DBD kidneys  showed no difference in 5-year graft survival . Increasing donor or recipient age, repeat transplantation, and CIT >12 h were associated with worse graft survival for recipients of DCD kidneys. Subsequent analyzes demonstrate equivalent 5-year patient survival or 10-year death-censored graft survival comparing DCD versus DBD kidneys (p = 0.21)  in 2005 to 1.47 IQR 1.16–1.90) in 2015, driven by increased donor age, hypertension, and use of DCD kidneys –1.90 in .However, caution should be exercised with the KDRI. It contains components which can increase the risk quantification score but now demonstrate comparable outcomes . Translatability of the KDRI to population cohorts outside the United States may not be valid ,39. Due Donor age has the strongest independent association with long-term kidney transplant outcomes . These a2 respectively, p < 0.001) . However, dual kidney transplantation did result in slightly higher 1-year estimated glomerular filtration rate [eGFR] (40 versus 36 ml/min/1.73 m< 0.001) .p = 0.003) and Black  donated kidneys independent of recipient ethnicity, with no survival advantage from donor-recipient ethnicity matching , obese , and morbidly obese  donors when compared to normal donor BMI group. However, donor BMI did not influence long-term patient or graft survival. This is corroborated with data from the United States. In a study of 6,932 recipients of DCD kidneys in the United States, Ortiz et al. reported donors with a BMI between 30.0–34.9 kg/m2 incurred 1.77-fold increased odds of developing DGF, with similar odds for DGF in donors with a BMI between 35.0–39.9 kg/m2   relative to a normal donor BMI category.In a population cohort study from the United Kingdom, Arshad et al. observed an independent association between donor BMI and delayed graft function , with ri< 0.001) . Howeverp = 0.009), which conflicts with other population-cohort studies that show inferior long-term patient and graft survival associated with larger recipients receiving smaller donor kidneys . DGF rates increased with severity of AKI . Primary nonfunction rates were higher with donor AKI stage 3 versus no AKI kidneys  and graft function was lower among donor AKI kidneys . This study differed from other cohorts due to its higher sample size, with a larger proportion of donor kidneys with severe AKI and donation after circulatory death, meaning this study may be better powered to observe differences in outcomes among donor kidneys with higher levels of injury. Other studies observed higher rates of graft failure only among a sub-select of studies using ECD donor kidneys with AKI , more primary nonfunction , no difference in eGFR in ml/min/1.732  and lower 1-year death-censored graft failure 14.5% versus 3.5% for AKI 2-3 versus AKI 0-1 high KDPI kidneys respectively   and high KDPI (≥85%) demonstrated more DGF  .Cohen et al. studied survival outcomes for kidney transplant patients receiving diabetic versus non-diabetic kidney allografts in the United States between 1994–2013 . RecipieThe critical question is whether waitlisted patients should accept diabetic donor kidneys versus waiting for better kidneys. Cohen et al. compared survival benefits of kidney transplantation using diabetic donor kidneys versus remaining on the waiting-list in the United States between 1994–2015 . They obp = 0.014) but not mortality .Donor hypertension is increasing in prevalence and observed in nearly a third of deceased donors . Altheabp = 0.011)  .Death by cerebrovascular accident remains the commonest cause of death, varying little across Europe between 2005–2015 , and conp = 0.008) , those who accepted IRDs had lower risk of death 1–6 months  and beyond 6 months   leading to morbidity or mortality occurred in only 0.96% of all solid organ transplantation in the United States . Increas< 0.001) .n = 32) of cases  among deceased donors can be classed as intravenous drug use (IVDU), imprisonment, or high-risk sexual behavior. Trotter et al, analyzing data from the United Kingdom between 2003–2015, studied the outcomes associated with use of IRB deceased donor kidneys . Donors The benefit of obtaining donor histopathology to guide kidney utilization is unclear. In a systematic review of published evidence, Wang et al. combined empirical evidence from 47 studies . In thesTranslating this evidence to nuanced decision-making is the big challenge. No guidelines or recommendations exist to support this process, which is difficult considering the nature of available data. For example, most deceased donors will have a combination rather than individual clinical factors see . This reHowever, this is a challenge due to the multi-factorial factors that influence post-transplant outcomes. Kerr et al., exploring data from the United States, quantified the magnitude of paired deceased donor effects when transplanted into different recipients . In analex situ (http://www.transplantmodels.com or https://www.odt.nhs.uk/transplantation/tools-policies-and-guidance/risk-communication-tools/for the US and UK respectively), they lack the machine learning capability or enhanced AI to provide more personalized risk probabilities.Developing and validating novel strategies and/or techniques to improve the process is therefore necessary. Various tools to aid decision-making are currently available or under investigation. These include donor risk scores in the setting of DCD kidneys , donor-rex situ , moleculex situ , and macex situ -92. The ex situ , but reqComplex deceased donor kidney offers, with time-pressured decision-making, can lead to unnecessary decline and/or discard of acceptable kidneys. By outlining donor clinical factors associated with post kidney transplant outcomes, the aim of this review is to support clinical decision-making. However, donor characteristics are only one component of a complex interplay that influence post-transplant outcomes. While any kidney allograft may not be better than no kidney allograft in every clinical scenario, the objective evidence would argue most kidney allografts are better than being denied the opportunity of kidney transplantation if deemed suitable for waitlisting.


The characteristic morphological parameters (bony posterior fossa volume (bony-PFV), posterior fossa crowdness, cerebellar tonsillar hernia, and syringomyelia) and CSF dynamics parameters at the craniocervical junction (CVJ) in Chiari malformation type I (CMI) were measured. The potential association between these characteristic morphologies and CSF dynamics at CVJ was analyzed.A total of 46 cases of control subjects and 48 patients with CMI underwent computed tomography and phase-contrast magnetic resonance imaging. Seven morphovolumetric measures and four CSF dynamics at CVJ measures were performed. The CMI cohort was further divided into “syringomyelia” and “non-syringomyelia” subgroups. All the measured parameters were analyzed by the Pearson correlation.P < 0.001) in the CMI group. Otherwise, the PCF crowdedness index  and the peak velocity of CSF (P < 0.05) were significantly larger in the CMI cohort. The mean velocity (MV) was faster in patients with CMI with syringomyelia (P < 0.05). In the correlation analysis, the degree of cerebellar tonsillar hernia was correlated with PCF CI , MV , and the net flow of CSF . The Vaquero index was well correlated with the bony-PFV , MV , and the net flow of CSF .Compared with the control, the posterior cranial fossa (PCF) area, bony-PFV, and CSF net flow were significantly smaller (The bony-PFV in patients with CMI was smaller, and the MV was faster in CMI with syringomyelia. Cerebellar subtonsillar hernia and syringomyelia are independent indicators for evaluating CMI. Subcerebellar tonsillar hernia was associated with PCF crowdedness, MV, and the net flow of CSF at CVJ, while syringomyelia was associated with bony-PFV, MV, and the net flow of CSF at the CVJ. Thus, the bony-PFV, PCF crowdedness, and the degree of CSF patency should also be one of the indicators of CMI evaluation. Chiari malformation type I (CMI) is diagnosed when the cerebellar tonsil exceeds the foramen magnum (FM) by 5 mm on magnetic resonance imaging (MRI) , 2. ThisPhase-contrast magnetic resonance imaging (PC-MRI) has been rigorously developed, and the study of CSF dynamics is no longer limited to the anatomical perspective but to recognize and study the CMI disease dynamically, but the exploration of CSF dynamics is still unclear. We often observe patients with CMI with mild cerebellar tonsillar hernia , and somThere are few reports about the correlation between the morphological changes in CMI and CSF dynamics , 17, andApproval for this study was obtained from our institutional review board, and consent was obtained from all subjects. Seventy-three hospitalized and surgically treated adult patients were retrospectively evaluated from January 2019 to January 2022, and hospitalized adults diagnosed with unruptured intracranial aneurysms matched for sex and age served as the control group. All enrolled subjects underwent thin-layer CT and PC-MRI examinations of the neck. All data were measured preoperatively.The inclusion criteria were as follows:Primary diagnosis as CMI : the cerAge over 16 years.The exclusion criteria were as follows:Basilar invagination (BI) , atlantoAcquired CMI or spinal cord malformation, such as hydrocephalus, intracranial neoplasm, or tethered spinal cord.A history of skull or spinal trauma or surgery.Thin-slice CT imaging was performed on a 128-slice multidetector scanner  with a thickness of 0.5 mm. As described previously , the bonPhase-contrast magnetic resonance imaging was performed using a 1.5T scanner . The hydrodynamics of CSF measured during a cardiac cycle consisted of 36 phase and amplitude maps. The coding speed was 12 cm/s, the thickness was 4 mm, the reverse corner was 15°, and the direction of speed coding was cranial to caudal.(1) Tonsil descent: the distance between the lowermost margin of the cerebellar tonsils and McRae's line.(2) Syrinx length: the number of segments that syrinx span the spinal cord.(3) VI : Vaquero(4) HB area: hindbrain area, the area of the cerebellum and the brainstem on a midsagittal MRI image, excluding herniated tonsils.(5) PCF area: posterior cranial fossa area, the area bordered by the clivus, the tentorium, the occipital bone, and the FM on MRI in the midsagittal view.(6) PCF CI: PCF crowding index, calculated as HB/PCF × 100%.(7) Bony-PFV : definedmax: maximum positive velocity, the maximum cranial velocity of CSF at FM in a cardiac cycle.(8) PVmax: maximum negative velocity, the maximum caudal velocity of CSF at FM in a cardiac cycle.(9) NV(10) AbsMV: the absolute value of the mean velocity.(11) Net flow: the net CSF flow at FM during a cardiac cycle.Test–retest reliability was repeatedly measured within 2 weeks by two neurosurgery residents (S.X. and Y.B.R.), and the average value of the two groups was recorded and analyzed , 2.t-test was used to determine the significance of the measures between control groups and patients with CMI between CMI with and without SM. The chi-square test compared count data between the two groups. The Pearson correlation analysis was used to investigate the morphological and physiological indices. Statistical analyses were performed using IBM SPSS software version 25.0 . Significance was indicated by a P < 0.05. For the multiple corrections, the false discovery rate (FDR) was used based on the Benjamini–Hochberg procedure  or sex (P = 0.137). The CMI group presented with cough-related occipital headache (54.2%), limb numbness (50%), neuropathic pain (22.9%), sensory disturbances (20.8%), muscle weakness (25%), amyotrophy (2%), and choking or hoarseness on drinking water (2%).A total of 48 patients  in the CMI group and 46 control subjects  were included in this study. There was no difference in age , bony-PFV (P < 0.001), and net flow (P < 0.001) were significantly smaller in the CMI cohort. The PCF CI (P < 0.001), PVmax (P < 0.05), and NVmax (P < 0.05) in the CMI cohort were higher than those in the control group. There were no significant differences in the HB area (P = 0.066) or absMV (P = 0.254) between the two groups.In the CMI group, the cerebellar tonsillar hernia was (9.85 ± 0.74) mm, and the syrinx was across the level of the spinal cord (7.03 ± 0.46), VI was (64.79 ± 3.25). Compared with the control group, the PCF area (P < 0.05) was significantly higher in the SM group. Bony-PFV was smaller in the SM group (127.36 ± 4.87 ml) than in the non-SM group (134.77 ± 3.39 ml) though the difference was not statistically significant (P = 0.316).A total of 43 patients (89.6%) were complicated with SM in the enrolled CMI cohort . ComparePearson correlation coefficients and P-values are listed in R = −0.468, P < 0.01). The correlation that reached a moderate level was between bony-PFV and VI . Similarly, PCF CI was also weakly correlated with tonsil descent , PVmax , absMV , and net flow . However, neither tonsil descent  nor the degree of patency of CSF was significantly associated with bony-PFV.The indicators related to PCF are represented by PCF CI and bony-PFV. There was a significant correlation between bony-PFV and PCF CI  and net flow , while there was no correlation with syrinx expansion.In addition to PCF CI, tonsil descent was slightly associated with absMV  and absMV  and moderately correlated with CSF net flow . However, the degree of syrinx expansion was not correlated with the degree of tonsil descent.The degree of syringomyelia was measured by syrinx length and VI. The results showed that VI was slightly correlated with bony-PFV . Similarly, the absMV was correlated with tonsil descent , VI , and PCF CI . In addition, CSF net flow was correlated with tonsil descent , VI , and PCF CI .In this analysis, PVThe pathogenesis of CMI remains unclear, and a theory of bone dysplasia has been proposed since the malformation of PFV cannot match the normal development of the posterior fossa nerve tissue, resulting in cerebellar tonsillar hernia down into the spinal canal, and disordered circulation of CSF at CVJ. However, this theory cannot fully explain the pathology of CMI. The data from different studies are inconsistent; some studies have shown a smaller PCF in adults with CMI , 24–28, In previous studies, we described the underdeveloped clivus and occipital bone as well as a reduction of the volume of bony PCF in adults with CMI . We alsoP < 0.05 was considered significant. The FDR correction was for reference on account of the limited sample size.Pearson correlation analysis was performed for morphological and physiological measures, and a P < 0.001). In addition, MRI sagittal images were used to measure PCF crowdedness, which is well correlated with bony-PFV , and linear PCF measurement is a supplement to volumetric measurement (P < 0.001), which demonstrates that the PFV was disproportionate to its contents and suggests that a better feature of CMI is the bony volume and crowdedness of the PCF, which is consistent with previous reports , but there was no significant difference, and there was no difference in the bony-PFV, PCF CI, CSF peak velocity, or net flow at CVJ. The most notable finding is that the absMV in the CMI-SM group was higher than that in CMI without SM. This illustrates that the formation of syringomyelia has a close relationship with CSF circulation, and the examination of CSF dynamics is critically important. Changes in CSF circulation can be used to prospectively predict the direction of disease progression.Approximately 89.6% of patients with CMI had syringomyelia, which was similar to previous reports . When thPrevious studies have been limited to correlation analysis between PCF size and CSF flow . In our max of CSF. This confirmed that the congestion of the PCF may be one of the factors contributing to the downward herniation of the cerebellar tonsils into the spinal canal. The prolapse of the cerebellar tonsils exacerbates the stenosis of CVJ, and the CSF circulation is blocked.Among the parameters of PCF, the VI is the only parameter that is correlated with the bony-PFV, which suggests that patients with CMI whose bony-PFV are small are more prone to syringomyelia in the course of the disease. If abnormal narrowness of bony-PFV is found in the early stage of clinical diagnosis and treatment, close follow-up and vigilance should be increased, and intervention should be implemented in the early stage of syringomyelia progression. Interestingly, the severity of cerebellar tonsillar hernia was disproportionate to the bony-PFV. Therefore, we further measured the PCF CI and found that it was potentially correlated with cerebellar tonsillar hernia and PVAmong the relevant parameters of syringomyelia, the syrinx length seems to have no correlation with any of the parameters measured here. The VI was not only related to the bony-PFV but also related to the velocity of CSF, and even the net flow of CSF reached a moderate degree of correlation. This result suggests that the alteration of the high dynamic CSF flow of CMI may play an important role in the pathogenesis of syringomyelia.In the correlation analysis of cerebellar tonsillar hernia, PCF crowdedness, absMV, net flow of CSF, and tonsillar hernia all reached a relevant level. This result suggests that the cerebellar tonsillar hernia in patients with CMI may be the result of the combined effect of PCF crowding and CSF changes. This is, indeed, clinically true; however, some patients have a “spacious” PCF, but severe cerebellar tonsillar hernia can still be observed. This may be related to CSF circulation disorder, and the choice of future treatment strategy should take the PCF bony volume, crowdedness, and CSF circulation factors into consideration. In addition, we noted that cerebellar tonsillar hernia was negatively correlated with absMV. We hypothesized that the more severe the cerebellar tonsillar hernia, the more crowded the CVJ, and the decrease in net flow, and the CSF flow becomes more disrupted and the lateral fluid offsets some of the energy along the flow direction, thus showing a decrease in mean flow velocity.Among the hydrodynamic parameters of CSF at FM, as mentioned earlier, the absMV and net flow were weakly correlated with the degree of PCF CI, cerebellar tonsillar hernia, and VI. Lower herniated cerebellar tonsils and crowded PCF are often accompanied by faster CSF velocity and less CSF net flow, while high hydrodynamic velocity and high flow of CSF are closely related to syringomyelia formation.The bony-PFV in patients with CMI was smaller, and the MV was faster in CMI with syringomyelia. Cerebellar subtonsillar hernia and syringomyelia are independent indicators for evaluating CMI. Subcerebellar tonsillar hernia was associated with PCF crowdedness, MV, and the net flow of CSF at CVJ, while syringomyelia was associated with bony-PFV, MV, and the net flow of CSF at CVJ.The bony-PFV, PCF crowdedness, and the degree of CSF patency should be considered as combined indexes in the evaluation of patients with CMI.This study provides some clues for the clinical evaluation and treatment of patients with CMI by quantifying the changes in bony-PFV, PCF crowding, cerebellar tonsillar hernia, syringomyelia, and CSF circulation at CVJ.1) Cerebellar tonsillar hernia in patients with CMI may be the result of the combined action of PCF and CSF changes. If only the bony-PFV decreased or the PCF was crowded and the CSF PC-MRI examination did not detect an increase in CSF velocity or a decrease in net flow at CVJ, the diagnosis and treatment plan would be mainly to increase the PCF space with bone decompression.2) If the bony-PFV or PCF CI is within the normal range but the CSF cine indicates increased CSF velocity or decreased net flow at CVJ, subdural decompression or dilated duralplasty may be further performed to improve CSF circulation.3) If the patient not only has a narrow PCF but also has CSF circulation disorder, the diagnosis and treatment plan should also take into account the expansion of bony-PFV and the clearing of CSF circulation disorder. On the basis of subarachnoid decompression, a part of the cerebellar tonsils can be removed under the pia soft membrane for more complete decompression.There are several limitations of this study that need to be considered when analyzing the results. First, due to the limited number of samples, this study failed to analyze the possible influence of race, sex, and other factors on these parameters. Second, this study did not include asymptomatic patients or patients with cerebellar tonsillar hernias smaller than 5 mm, which should be investigated in future studies. Finally, this study provides a new direction for thinking about surgical strategies through correlation analysis of the parameters. The realization of this goal requires a large number of patients to receive surgical treatment and long-term follow-up during the study period.The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.The studies involving human participants were reviewed and approved by Ethics Committee of Beijing Sanbo Brain Hospital. The patients/participants provided their written informed consent to participate in this study.Conception and design: SW and TF. Acquisition of data: SW and KW. Drafting the article and approved the final version of the manuscript on behalf of all authors: SW. Statistical analysis: SW, DZ, and KW. Study supervision: TF. Analysis and interpretation of data, critically revising the article, and reviewed submitted version of manuscript: All authors. All authors contributed to the article and approved the submitted version.