Dorothée Lulé
email: dorothee.lule@uni-ulm.de

Diekmann

Volker

Hans-Peter Müller

Jan Kassubek

Albert C Ludolph

Birbaumer

Niels

Neuroimaging of multimodal sensory stimulation in Amyotrophic Lateral Sclerosis (ALS)

Keywords: fMRI, DTI, ALS, Sensory (visual/auditory/somato-sensory), reorganization

Aim: Structural and functional imaging techniques were combined to investigate sensory system function in amyotrophic lateral sclerosis (ALS).

Methods: Functional magnetic resonance imaging (fMRI) was used to investigate cortical activity during visual, auditory, and somato-sensory stimulation in fourteen ALS patients and eighteen control subjects. Changes in amplitude, latency and duration of the BOLD response were modelled. Furthermore, diffusion tensor imaging was used to investigate changes in white matter networks.

Results: During visual stimulation, fMRI demonstrated a decreased response in secondary visual areas in ALS possibly related to demyelination of sensory nerve fibres. Increasing brain activity in associative cortices was linked to decrease in physical functioning and might represent a compensatory process. Additionally, reduced white matter functioning became evident for fibres projecting to extrastriate visual cortex.

For auditory stimulation, a delayed response in secondary auditory areas probably linked to prolonged nerve conductance time and an altered cortical pattern in areas involved in target processing/detection became evident in ALS patients.

Structural white matter changes in the primary and secondary auditory cortices were observed.

For somato-sensory stimulation a prolonged/reduced response in sensory integration areas of the parietal lobe was observed perhaps linked to the reduced visceral inflow due to immobility. Conclusion: Multiparametric MRI suggests a progressive functional deficit in secondary/higher order sensory processing areas in ALS, probably associated with reduction of re-afferent information flow due to progressive immobility. The changes described might as well represent an expression of the disease process itself. Evidence for compensatory processes in multimodal associative cortices was found.

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a progressive degenerative disease of the upper and lower motor neurons. There is ample evidence for degeneration not restricted to the motor system. [START_REF] Maekawa | Cortical selective vulnerability in motor neuron disease: a morphometric study[END_REF] In different groups of ALS patients, alterations in non-motor areas were observed by volumetric/morphometric studies [START_REF] Kassubek | Global brain atrophy and corticospinal tract alterations in ALS, as investigated by voxel-based morphometry of 3-D MRI[END_REF][START_REF] Sach | Diffusion tensor MRI of early upper motor neuron involvement in amyotrophic lateral sclerosis[END_REF] and in histopathological studies. [START_REF] Isaacs | Amyotrophic lateral sclerosis with sensory neuropathy: part of a multisystem disorder?[END_REF][START_REF] Hammad | Clinical, electrophysiologic, and pathologic evidence for sensory abnormalities in ALS[END_REF] Electrophysiological evidence for functional alterations of the sensory system such as slower nerve fibre conductance was provided [START_REF] Hammad | Clinical, electrophysiologic, and pathologic evidence for sensory abnormalities in ALS[END_REF][START_REF] Pugdahl | Generalised sensory system abnormalities in amyotrophic lateral sclerosis: a European multicentre study[END_REF], probably associated with demyelination. A reduced and delayed response to auditory and visual stimuli was observed in early sensory cortical processing areas in ALS patients. [START_REF] Münte | Alteration of early components of the visual evoked potential in amyotrophic lateral sclerosis[END_REF][START_REF] Münte | Abnormalities of visual search behaviour in ALS patients detected with event-related brain potentials[END_REF] Clinically, a subgroup of patients reports sensory symptoms (22% with numbness and neuropathic pain) and abnormalities on sensory examination (20% with diminished vibration sense). [START_REF] Hammad | Clinical, electrophysiologic, and pathologic evidence for sensory abnormalities in ALS[END_REF] The electrophysiologic and pathologic findings indicate a pattern of demyelination and axonal loss in the sensory systems which may occur independently of motor system degeneration.

Evidence for non-neuronal cell involvement in ALS such as in astrocytes increased over the last years. [START_REF] Julien | ALS: astrocytes move in as deadly neighbors[END_REF] Decreased glutamate uptake by astrocytes results in motorneuron overload and finally in terminal retraction of the neuron from the effector i.e. the muscle. [START_REF] Boillée | ALS: a disease of motor neurons and their nonneuronal neighbors[END_REF] Similar mechanisms can be expected for other glutamatergic neurons e.g. in the sensory systems.

The pathological findings in the sensory system may as well be a result of reduced external information flow due to progressive immobility in ALS (less movement causes less information about body part positions to be processed in the brain) following the concept of the 'somatic marker hypothesis'. [START_REF] Damasio | Somatic markers and the guidance of behaviour: theory and preliminary testing[END_REF] In order to further investigate functional and structural changes in the sensory pathway in ALS, functional magnetic resonance imaging (fMRI) in the present study measured activity patterns of the brain during multimodal sensory stimulation (visual, auditory and tactile stimuli) in ALS patients and controls.

Diffusion tensor imaging (DTI) was used to analyse alterations of fibre tracks projecting into sensory processing areas.

The understanding of how the sensory brain changes in association with ALS may help us with some behavioural problems and perceptual deficits on the one hand, i.e. why patients without voluntary motor control have not been able to control Lulé -4brain computer interfaces (BCIs). [START_REF] Kübler | Brain-computer interfaces and communication in paralysis: Extinction of goal directed thinking in completely paralysed patients?[END_REF] On the other hand, progressive sensory deprivation may mark some of the motor-social deteriorations. A life less driven by external stimuli may contribute to the surprisingly high quality of life even in endstage patients. [START_REF] Lulé | Ergebnisse zu Depression und Lebensqualität bei der amyotrophen Lateralsklerose. Deutsches Ärzteblatt[END_REF] Lulé -5 -

MATERIAL AND METHODS

Participants

Fourteen ALS patients participated in the study (6 women and 8 men; mean age 54.7±13 years, 39-67 range). Probable (N=7) or definite ALS (N=7) was diagnosed according to the revised El Escorial criteria (Brooks 1998). All cases were sporadic forms with spinal onset, none of the patients exhibited major bulbar symptoms.

Mean duration of the disease was 28.0±26.8 months (range 4-96 months), as determined by the onset of motor symptoms. Mean clinical severity of ALS was 33.4±8.2 (range 18-44) as measured by the ALS functional ratings scale (revised form, ALSFRS-R); [START_REF] Cedarbaum | The ALSFRS-R: a revised ALS functional rating scale that incorporates assessments of respiratory function. BDNF ALS Study Group (Phase III)[END_REF] all patients were still able to walk; two patients were intermittently treated by non-invasive positive pressure ventilation.

Neuropsychological tests were conducted to control for clinically relevant depression or major cognitive deficits, both of which were exclusion criteria (mini mental state examination cut-off score <24 [START_REF] Folstein | Mini-Mental-State: A practical method for grading the cognitive state of patients for the clinician[END_REF] and ALS Depression Index 12 items cut-off score >28, [START_REF] Kübler | Ein Fragebogen zur Messung von Depression bei degenerativen neurologischen Erkrankungen (amyotrophe Lateralsklerose) -A questionnaire to measure depression in degenerative neurological diseases[END_REF] respectively.

Eighteen healthy volunteers (11 women and 7 men) were age-matched (mean age 59.6±8.3, range 42-70, T=1.26 p=0.22).

In 10 of the ALS patients (mean age 52.6±14.9 years, range 39-67), diffusion tensor imaging (DTI) measurements were acquired. Ten control subjects (mean age 53.7±11.5 years, T=0.22 p=0.83) were matched for DTI patients. The other participants did not tolerate the additional measurements.

The participants were all right-handed. None of the patients and control subjects had a history of psychiatric disorder, and all were free of central nervous system medication. Twelve ALS patients received Riluzol for medication. This might have asthenia and sleepiness as a possible side effect. Neither was reported by the patients as a major impact on daily living.

The study was approved by the Ethics Committee of the University of Ulm, and all participants gave written informed consent for the study.

Magnetic resonance imaging (MRI)

Functional, anatomical and diffusion weighted images were acquired on a 1.5 Tesla whole body scanner (Symphony, Siemens, Erlangen, Germany). DTI measurements were performed subsequent to the fMRI measurements.

Functional magnetic resonance imaging (fMRI)

Functional images were collected in trials using T2*-weighted gradient echo planar imaging (EPI) sequences (echo time, TE=50 ms, time repetition, TR=2.82s, flip angle 90°). Thirty-two slices (3.5mm slice thickness, 0.5mm gap, in plane resolution of 3.59x3.59 mm 2 , 64x64x32 voxel matrix) were acquired. Axial slice orientation aligned with the anterior-posterior commissure was chosen. The first 5 volumes of each sequence were discarded. T1-weighted anatomical images were collected using a high resolution 3-D sequence (TE=3.9ms, TR=1740ms, flip angle 15°; voxels size 0.9x0.9x0.9mm 3 , 256x256x192 voxels).

Design

An event-related design was used optimised for maximal BOLD signal amplitude. [START_REF] Robinson | BOLD responses to stimuli: dependence on frequency, stimulus form, amplitude, and repetition rate[END_REF] Stimuli were presented in blocks of 14s duration which consisted of stimulus epochs of 5s (three stimuli of about 1s interleaved by rest epochs of about 1s) and followed by a rest period of 9s. There were 26 stimulation blocks per trial. In total, three types of blocks were performed: in the first trial using a visual, in the second one an auditory and in the third a somato-sensory (tactile) paradigm.

In the visual paradigm an alternating checkerboard was presented via video goggles (flicker rate 0.3s). During the rest periods of the visual trial and during the total acoustic and tactile trials a black screen with a red fixation cross was presented. In the auditory part, 400 Hz sine wave tones were presented via headphones (50ms bursts every 500ms). Finally, a tactile stimulus was applied via a coil of 2 cm length fixated on the right index finger which vibrated with a frequency of 250 Hz (150ms bursts every 500ms). To keep the participant attentive during fMRI scanning, five slightly deviant stimuli were presented during each trial at pseudo random time instances (visual paradigm: contrast decreased from 100% to 50%; auditory paradigm: three 408 Hz or 392 Hz tones; tactile Lulé -7paradigm: five 150 Hz bursts). After each trial the participants were asked how many deviant stimuli had been perceived (expected verbal response was 5).

A two-way ANOVA was used to reveal group differences (ALS patients vs. controls) in target detection rate (deviant stimuli), and p<0.05 (two-tailed) was adopted for statistical significance.

fMRI data analysis

Image processing was performed using SPM2. [START_REF] Friston | Statistical parametric maps in functional imaging: a general linear approach[END_REF] Correction for temporal differences in acquisition time and for movements of the subject's head during scanning was applied. Functional data were co-registered with the anatomical scans, transformed into stereotactic space (Montreal Neurological Institute, MNI; http://www.ihb.spb.ru/~pet_lab/MSU/MSUMain.html) and resampled to a 3 mm isometric voxel size. Data were smoothed with an isotropic Gaussian kernel (7.2 mm full width at half maximum). The time series of the BOLD data were modelled by general linear models (GLM).

Contrast images from an 'informed' basis set were used, consisting of the canonical hemodynamic response function (hrf) and its two partial derivatives with respect to time and dispersion. [START_REF] Henson | Efficient experimental design[END_REF] The voxel time series were high-pass filtered (time constant 141 s) and the noise component in the model was described by a first-order autoregressive model.

Statistical analysis of fMRI data

Weighting factors of the sensory response regressors for each participant and trial were computed. Individual parametric maps (F-test uncorrected p < 0.001) were subjected to a second level group analysis between groups by use of a two-way ANOVA between groups for ALS patients vs. controls for the hrf and time and dispersion derivatives. The association between BOLD response (hrf alone) in every condition and level of functional impairment (ALSFRS score) was tested using a second level analysis of simple regression implemented in SPM2. Only areas with a significance of uncorrected p<0.001 at voxel level and with a cluster threshold > 5 voxels were considered significant.

Lulé -8 -

Diffusion tensor imaging (DTI)

Echo-planar imaging (EPI) MRI sequences were used. The DTI study protocol consisted of 13 volumes (45 slices, 128x128 pixels, slice thickness 2.2 mm, pixel size 1.5 mmx1.5 mm) representing 12 gradient directions and one scan with gradient 0 (TE=93ms, TR=8000ms, b-value=800s/mm 2 ). Four scans were k-space averaged online by the Siemens standard DTI protocol.

Data analysIs

DTI data were analysed using the tensor imaging and fiber tracking software (TIFT). [START_REF] Müller | Preservation of Diffusion Tensor Properties during Spatial Normalization by use of Tensor Imaging and Fiber Tracking on a Normal Brain Database[END_REF] In DTI images, the amount of diffusion, the extent of directedness, and the spatial direction of proton displacement was quantified in the fractional anisotropy (FA). [START_REF] Basser | MR Diffusion Tensor Spectroscopy and Imaging[END_REF] Spatial normalisation using a template for each group was used following the protocol of Müller et al. [START_REF] Müller | Preservation of Diffusion Tensor Properties during Spatial Normalization by use of Tensor Imaging and Fiber Tracking on a Normal Brain Database[END_REF] FA maps were arithmetically averaged for ALS patients and control subjects.

Smoothing of FA maps was performed with a 6 mm Gaussian kernel. [START_REF] Müller | Preservation of Diffusion Tensor Properties during Spatial Normalization by use of Tensor Imaging and Fiber Tracking on a Normal Brain Database[END_REF] Voxels with FA-values<0.2 were defined as cortical grey matter). Group differences were analysed by t-test between groups, thresholded at uncorrected p<0.05 and a cluster-extension of 15 voxels. Further details of postprocessing are described in Müller et al. [START_REF] Müller | Preservation of Diffusion Tensor Properties during Spatial Normalization by use of Tensor Imaging and Fiber Tracking on a Normal Brain Database[END_REF] Lulé -9 -

RESULTS

Neuropsychology

None of the participants met the exclusion criteria for dementia or depression (mean scores±standard deviation ALS patients: MMST=29.14±1.46; ADI-12=20.69±4.07; controls: MMST=29.2±1.15; ADI-12=18.00±4.42).

Performance of correct responses during sensory paradigms

Concerning correct response rates, ALS patients performed at the same level as controls in deviant target detection for visual (F=0.14 p=0.71) and auditory stimuli (F=0.14 p=0.71). For tactile stimuli, target detection was reduced in ALS patients, but the difference did not reach statistical significance (F=3.04 p=0.09).

Differences of BOLD response modelled with hrf between ALS patients and controls

For visual and somato-sensory stimulation, ALS patients presented no area with an increased BOLD response compared to control subjects. During auditory stimulation, ALS patients showed an increased BOLD acitivity in the caudate nucleus and in the middle frontal gyrus bilaterally (BA6; Table 1).

Healthy participants showed a higher BOLD activity for visual stimulation in the occipital lobe (V3a, BA19) of the right hemisphere and for auditory stimulation in the inferior frontal gyri of the right (BA45) and left hemispheres (BA6,9) compared to ALS patients (Table 1). Furthermore, a significantly higher BOLD activity was observed in the right-sided cerebellum of healthy compared to ALS patients. For somato-sensory stimulation, no difference became evident.

Regression analysis of BOLD and level of physical functioning in ALS patients

During visual stimulation in the ALS patient sample, BOLD activity in the superior parietal lobes of both hemispheres (BA7) and the inferior parietal lobe of the left hemisphere (BA40) significantly increased with the loss of physical functioning (Table 3, Figure 1A).

Likewise, reduced BOLD activity in the occipital lobe (TEO, BA19) of the right hemisphere (Table 3, Figure 1B) was significantly associated with decreased ALSFRS.

In ALS patients, BOLD in the inferior parietal gyrus (BA39,40) of the left hemisphere and in the middle frontal and precentral gyri (BA6,8,9) of the right hemisphere increased significantly with the loss of physical functioning during auditory stimulation.

Also, reduced BOLD activity in putamen, posterior insular cortex (BA13) and inferior parietal lobe (BA40) of the left hemisphere was significantly associated with decreased physical function (Table 3).

In the ALS patient group, higher BOLD activity in the middle temporal lobe (BA37) of the left hemisphere was significantly associated with the loss of physical functioning during somato-sensory stimulation.

In addition, reduced BOLD activity during somato-sensory stimulation in the thalamus and inferior parietal lobe (BA39) of the right hemisphere and in the inferior frontal gyrus (BA44) and posterior cingulate cortex (BA31) of the left hemisphere was significantly associated with decreased physical functioning (Table 3).

DISCUSSION

The aim of the present study was to combine functional and structural imaging techniques in order to investigate visual, auditory and somato-sensory system functioning in amyotrophic lateral sclerosis.

Visual system functioning in ALS

Compared to healthy controls, ALS patients showed a reduced/altered response in the secondary visual cortex: a reduced BOLD response in the area V3a and prolonged BOLD onset latency in V4, two areas known to be involved in processing of line contrasts and checkerboard. [START_REF] Kastner | Texture segregation in the human visual cortex: A functional MRI study[END_REF] Furthermore, ALS patients presented reduced BOLD activity in the secondary visual area TEO associated with level of physical impairment. TEO is again a secondary visual area for texture defined boundaries detection. [START_REF] Kastner | Texture segregation in the human visual cortex: A functional MRI study[END_REF] It receives its main input from V4, an area with delayed responsiveness in the ALS group. This may indicate a reduced velocity of information transport in the visual cortex due to a decreased neuronal conductance velocity, probably associated with demyelination. [START_REF] Hammad | Clinical, electrophysiologic, and pathologic evidence for sensory abnormalities in ALS[END_REF][START_REF] Pugdahl | Generalised sensory system abnormalities in amyotrophic lateral sclerosis: a European multicentre study[END_REF] In a previous study, evidence for a progressively reduced activation of extra-striate areas over the course of ALS was found [START_REF] Lulé | Brain responses to emotional stimuli in patients with amyotrophic lateral sclerosis (ALS)[END_REF] and electrophysiological evidence for pathology of this area was reported. [START_REF] Münte | Alteration of early components of the visual evoked potential in amyotrophic lateral sclerosis[END_REF][START_REF] Münte | Abnormalities of visual search behaviour in ALS patients detected with event-related brain potentials[END_REF] With electrophysiological techniques, the latency of the P1 component of visual evoked potentials (VEP) generated by extra-striate areas [START_REF] Clark | Spatial selective attention affects early extrastriate but not striate components of the visual evoked potential[END_REF] was significantly delayed or nearly absent in ALS patients. [START_REF] Münte | Alteration of early components of the visual evoked potential in amyotrophic lateral sclerosis[END_REF][START_REF] Münte | Abnormalities of visual search behaviour in ALS patients detected with event-related brain potentials[END_REF][START_REF] Subramaniam | Multimodality evoked potentials in motor neuron disease[END_REF] Those findings may be subsumed as evidence for the above mentioned demyelination of nerve fibres in the optic tract projecting to the extrastriate visual areas in ALS.

BOLD activity in higher order sensory processing areas in the superior parietal lobe (BA7,40) increased with loss of physical function in ALS patients. This increased response in areas of visual oddball detection [START_REF] Ardekani | Functional magnetic resonance imaging of brain activity in the visual oddball task[END_REF] might either be associated with increased effort for deviant stimuli detection due to attention deficits in the ALS patient group, [START_REF] Ludolph | Frontal lobe function in amyotrophic lateral sclerosis: a neuropsychologic and positron emission tomography study[END_REF] but it might as well suggest a compensatory neuronal process for the functional impairments in secondary visual cortices.

Concerning structural changes, there were significantly less functional white fibre tracts projecting to secondary sensory areas (BA18,19) in the occipital lobe and in the inferior parietal lobe (BA40), supporting a close relationship between functional

Lulé -15and structural deficits in the visual processing pathway. Evidence for FA reduction in several extra-motor areas throughout the brain of ALS patients has been reported by other authors. However, there was a high variance of where FA differences were found. In those studies, different approaches and methods have been used, leading to conflicting and inconclusive results [START_REF] Sage | Quantitative diffusion tensor imaging in amyotrophic lateral sclerosis[END_REF] Sage and colleagues presented evidence that ALS-associated changes in DTI analysis are most probably not attributed to brain atrophy [START_REF] Sage | Quantitative diffusion tensor imaging in amyotrophic lateral sclerosis[END_REF] but rather present functional changes of the fibre tracts. Accordingly, the changes in FA in the visual pathways of ALS patients probably present functional changes of the fibre tracts which may go in line with the above mentioned reduced velocity of information transport in the visual system.

Additionally, Sage and colleagues provided evidence that FA changes in ALS are associated with disease progression but not with disease duration, supporting the existence of a heterogeneous disease process in ALS. [START_REF] Sage | Quantitative diffusion tensor imaging in amyotrophic lateral sclerosis[END_REF] This may additionally explain differences in DTI findings in several studies with ALS patients.

Auditory system functioning in ALS

In the auditory modality, ALS patients revealed delayed BOLD latency in secondary auditory areas (BA22) known to be involved in processing of tones [START_REF] Conway | Neural substrates related to auditory working memory comparisons in dyslexia: an fMRI study[END_REF] and a significant prolonged duration of the BOLD response in the bilateral supramarginal area (BA40) known to be involved in auditory discrimination [START_REF] Hodges | Aspects of multisensory perception: the integration of visual and auditory information in musical experiences[END_REF] which might imply slowed auditory information processing. The increased latency in the parahippocampal gyrus in ALS patients might as well be associated with cognitive/encoding difficulties in the deviant task. [START_REF] Xu | Perfusion fMRI detects deficits in regional CBF during memory-encoding tasks in MCI subjects[END_REF] Abnormalities in auditory evoked potentials were described as mild or rare in ALS. [START_REF] Chiappa | Brain Stem Auditory evoked potentials: interpretation[END_REF] However, changes of auditory ERPs in ALS patients compared to control subjects [33] might be affected by sensory processing deficits rather than by cognitive/attentional deficits alone.

Structures that are involved in multisensory information processing and target detection in tones such as the caudates [START_REF] Nagy | Multisensory integration in the basal ganglia[END_REF] and prefrontal cortex (BA6) [START_REF] Strobel | Novelty and target processing during an auditory novelty oddball: a simultaneous event-related potential and functional magnetic resonance imaging study[END_REF] showed increased BOLD activation in ALS patients. In contrast, ALS patients demonstrated a reduced BOLD response in inferior frontal cortical areas (BA6,45) and in the culmen of the right cerebellum during the same task, i.e. in areas associated with auditory target tone detection. [START_REF] Strobel | Novelty and target processing during an auditory novelty oddball: a simultaneous event-related potential and functional magnetic resonance imaging study[END_REF] The cognitive skill of deviant Lulé -16target tone detection in this study might be compromised by subclinical cognitive deficits known to be present in ALS patients and associated with frontal cortex functioning. [START_REF] Ludolph | Frontal lobe function in amyotrophic lateral sclerosis: a neuropsychologic and positron emission tomography study[END_REF] Accordingly, ALS patients might present a changed neuronal pattern for the cognitive task of auditory deviant stimulus detection. This interpretation was supported by the result that the BOLD response in the superior parietal lobe (SPL, BA40) and the posterior insular cortex (PIC), which are known to be involved in sound discrimination, showed decreased activity with physical function loss in ALS. Dysfunction of SPL and PIC might be compensated by increased activity in inferior parietal and superior frontal areas suggesting a changed pathway for deviant target detection associated with subclinical cognitive deficits in ALS patients.

Again, structural changes supported the functional findings in the auditory pathway such as reduced fibre tract functioning to primary and secondary sensory areas like BA21 in the right and BA22, 41 and 42 in the left hemisphere indicating white matter degeneration in secondary auditory areas and Wernicke`s area in ALS.

Evidence of involvement of the temporal cortices has not been reported previously and there has been yet no major clinical report on deficits in the auditory system of ALS patients. The hereby presented overlap of changes in fRMI and FA for the auditory pathway may again present the heterogeneous disease progression.

Somato-sensory system functioning in ALS

In the tactile paradigm, ALS patients showed a longer lasting BOLD response in the anterior insular cortex (AIC) compared to control subjects, indicative of increased nerve conductance time in the somato-sensory system. [START_REF] Hamada | Median nerve somatosensory evoked potentials and their high-frequency oscillations in amyotrophic lateral sclerosis[END_REF].

Impaired functioning of integrative sensory structures such as the thalamus, posterior cingulate cortex (PCC, receiving direct thalamic input) and inferior parietal lobe (BA39) [START_REF] Duncan | Is there a role for the parietal lobes in the perception of pain?[END_REF] was related to decay in physical functioning in ALS during somato-sensory stimulation. This may be linked to the diminished inflow to the "visceral cortices" caused by immobility and/or it may be an expression of the disease progress itself. Furthermore, activity in left inferior frontal lobe (BA44), an area involved in the representation of one's own body map, [START_REF] De Lussanet | Interaction of visual hemifield and body view in biological motion perception[END_REF] 2007). Furthermore, patophysiological involvement of secondary sensory areas may as well be suspected. The behavioural effect of this degeneration may not pass a clinical threshold. In advanced stages of ALS the reported compensatory activity in association areas might be compromised at a functional level by this denervation.

The possible side effect of Riluzol treatment like asthenia in the ALS patient group might have had some negative effect on the BOLD in this study. However, none of the patients complained about asthenia; furthermore DTI measurements are not expected to be confounded by those side effects.

Concluding, a complex pattern of reduced and increased brain activity in ALS was observed associated with white matter lesions. It may be associated with the reduced efferent and re-afferent information flow due to the loss of motor function.

Patient's social life and movement is often reduced to the radius of their home.

The abnormalities recorded among patients in the present study and in another study [START_REF] Hammad | Clinical, electrophysiologic, and pathologic evidence for sensory abnormalities in ALS[END_REF] were present relatively early in the course of their disease, at a stage when malnutrition and immobility were not significant complications of the illness.

Accordingly, the changes in the sensory system may be an expression of the Lulé -18disease process itself and/or a combination of loss of information flow and disease process.

Figure 1 :

 1 Figure 1: Changes in brain activity associated with loss of physical function in ALS

Figure 2 :

 2 Figure 2: White matter changes in ALS patients

Table 1 :

 1 DifferencesThe time derivative of the hrf indicated that ALS patients had an increased latency of the canonical response in the occipital lobe of the right hemisphere (V4, BA18,19; Table2) during visual stimulation compared to controls. During auditory stimulation, the hrf of ALS patients had a longer latency in the superior temporal cortex of the left hemisphere (BA22,42; Table2) and in the parahippocampal gyrus of the right hemisphere. During somato-sensory stimulation, ALS patients demonstrated no significant difference in the BOLD response regarding the time derivative.

	Experimental Cluster size		Anatomic Areas	Brodmann Area	MNI coordinates [mm]
	paradigm	(voxel)				x	y	z	T
		ALS patients higher BOLD response than controls
	Auditory	13	L and R Caudate nucleus		-3	3	12 4,33
		12	L and R Middle frontal gyrus	6	0	12	57 3,73
		Control group higher BOLD response than ALS patients
	Visual	12	R	Middle occipital gyrus	19	30	-84	24
	Auditory	11	R	Inferior frontal gyrus	45	48	24	6 5,25
		10	L	Inferior frontal gyrus	6, 9	-60	3	27 4,76
		16	R	Cerebellum		30	-72	27 4,82

in brain activity between ALS patients and control subjects Comparison between ALS patients and control subjects for BOLD response modelled with hrf for visual, auditory and somato-sensory stimulation. T-test During visual stimulation, ALS patients showed no significant difference in the BOLD response concerning dispersion derivative (dv). During auditory stimulation, group differences in dv of the hrf indicated that ALS patients had a prolonged hrf response compared to the hrf response of the control group in the supra-marginal gyri (BA40) of both hemispheres. During somato-sensory stimulation, ALS patients had a prolonged hrf response in the inferior frontal gyrus (BA45) and posterior insular cortex (BA13) of the right hemisphere (Table

2

).

ALS patients have longer latency of hrf compared to controls Visual 11 R Occipital lobe 18, 19 21 -72 -9 3,72 Auditory

	18	R Parahippocampal gyrus		36	-9	-21 5,77
	7	L Superior temporal gyrus	22, 42	-66	-15	6 5,

68 ALS patients have prolonged hrf compared to controls

	Auditory	26	L Supramarginal gyrus	40	-30	-48	45 7,44
		28	R Supramarginal gyrus	40	39	-48	39 6,75
	Somatosensory	15	R Inferior frontal gyrus, posterior insular cortex	13, 45	39	21	12 4,26

Table 2 :

 2 Differences in shape of brain response between ALS patients and control

subjects Comparison of BOLD response modelled with hrf and time and dispersion derivatives for visual, auditory and somato-sensory stimulation in ALS patients versus control subjects. T-test statistics, uncorrected threshold (p<0.001) was chosen. ALS, Amyotrophic lateral sclerosis; L, left hemisphere, R, right Lulé -11hemisphere; BOLD, blood oxygen level dependent; MNI, Montreal Neurological Institute coordinates.

Table 3 :

 3 Areas

	Lulé -12 -

with increasing/decreasing activity associated with physical function loss Regression analysis of BOLD activity with physical function (measured with ALS functional rating scale revised form, ALSFRS) in ALS patients for visual, auditory and somato-sensory stimulation. T-test statistics with uncorrected threshold (p<0.001) were chosen. ALS, Amyotrophic lateral sclerosis; L, left cerebral hemisphere, R, right cerebral hemisphere; BOLD, blood oxygen level dependent; MNI, Montreal Neurological Institute coordinates.

Acknowledgements

Alexander Unrath (University of Ulm) is thankfully acknowledged for his help in the course of the DTI experiments and data analyses. Special thanks to Sonja Fuchs (University of Ulm), Sandra Pauli (University of Ulm) and Femke Nijboer (University of Tübingen) for technical assistance in MRI measurements. We would like to thank Corinna Hendrich, Regina Gastl and Anne Sperfeld (all University of Ulm) for supporting us in the recruitment of patients. Special thanks to the patients who participated in this study. None of the authors reports any competing interests. The work was funded by the german research foundation (Deutsche Forschungsgemeinschaft).

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James Lind Alliance

Identifying and prioritising epilepsy treatment uncertainties

Objective

To identify and prioritise uncertainties regarding epilepsy treatment from people with epilepsy, their carers and from epilepsy clinicians. treatment programmes for non-epileptic attack disorder (NEAD), concerns about sideeffects in utero and uncertainties regarding prescribing in pregnancy.

Conclusions

Patient uncertainties were often focussed on very practical considerations -how to take prescribed medication, access to services and how to minimise drug side effects. Clinicians' questions were also practical but clustered around 'the challenging consultation' e.g. NEAD, sudden unexplained death in epilepsy (SUDEP) and prescribing in pregnancy. We have published the research questions on NHS Evidence, and are working with them to identify those questions which represent genuine uncertainties. We encourage other clinicians to seek patient and carers' priorities in order to shape their research agenda.

Background

Failure to acknowledge and address genuine treatment uncertainties has caused unnecessary iatrogenic harm. We define an uncertainty as a question that cannot be sufficiently answered by a systematic review of the literature. The database of the uncertainties of the effects of treatment (DUETs) is a collection of 'known unknowns' that enables patient-prioritised research.

Design and Participants

We organised five separate focus groups (two consisting of clinicians, three of patients and carers) to garner questions on epilepsy treatment uncertainties; these yielded 398 potential research questions. Participants were asked to rank the questions in terms of importance. We then performed a thematic analysis.

Results

Patients rated questions concerning cognitive drug side-effects, managing the consequences of side-effects and improving public awareness about the treatment of epilepsy through improved services as most important. For clinicians, the most important themes were Introduction It is often unclear how research topics are chosen and prioritised. Industry-sponsored projects may be selected to display their product to advantage [START_REF] Tallon | Relation between agendas of the research community and the research consumer[END_REF][START_REF] Garattini | Patients and the public deserve big changes in evaluation of drugs[END_REF] and availability of time, money and personnel may determine topics chosen for independent investigation. [START_REF] Scadding | Alliance: an opportunity for neurologists in therapeutic research?[END_REF] Grant committees rightly ask applicants to consider patients' views when submitting an application, but this is difficult without knowledge of exactly what is uncertain and which topics are patient priorities. Do funded research questions address the priorities of people with epilepsy? [4] Do they even reflect the uncertainties prioritised by clinicians? When prescribing for certain groups, e.g. people with epilepsy and learning disability, we often work in an evidence vacuum, extrapolating from relevant studies of related patient groups. Our comfort with uncertainty and our acceptance of this 'grey area' has unwittingly promoted a climate where immeasurable harm is perpetrated through labelling situations as "uncertain" where there is already sufficient evidence to make them certain; e.g., corticosteroids in head injury, [START_REF] Trial | Effect of intravenous corticosteroids on death within 14 days in 10,008 adults with clinically significant head injury (MRC CRASH trial): a randomised placebo-controlled trial[END_REF] caffeine for neonates [START_REF] Schmidt | Long-term effects of caffeine therapy for apnea of prematurity[END_REF] or prophylactic anti-arrhythmics after myocardial infarction. [START_REF] Furberg | Effect of anti-arrhythmic drugs on mortality after myocardial infarction[END_REF] The James Lind Initiative aims to promote "identification of the most important gaps in knowledge about the effects of treatments" through developing a database of uncertainties of treatments (DUETs), published on-line at NHS Evidence.[8] As part of this project we facilitated people affected by epilepsy and its treatment (patients, carers, clinicians and scientists) to create and prioritise treatment uncertainties.

Methods

Using qualitative methodology based upon the consultations in rheumatoid arthritis, [START_REF] Carr | Rheumatology outcomes: the patient's perspective[END_REF] we arranged five separate focus groups: three with patients and carers and two with clinicians and health professionals. The sequence of meetings was Cardiff professionals, Cardiff patients, Swansea professionals, Swansea patients and Cardiff patients; beyond geographical convenience there was no attempt to place people in specific focus groups for balance. Patients were invited from several sources: clinic appointments, previous involvement in local projects with the Wales Epilepsy Research Network (WERN), and membership of local charity groups. Involvement was voluntary and unpaid; meetings lasted 90 to 120 minutes. We did not discourage anyone from attending who expressed an interest in doing so. Participants were invited to try to ensure a balance of adult and paediatric, oligoepilepsy and refractory epilepsy, pre-and post-surgical candidates, people with learning disability, parents and children, carers and support workers (see Box 1). Carers (34-69 years) Dietician (1) Each meeting had the same agenda and two of us were present to write the questions onto an overhead projector and to chair the discussion. The focus groups were asked to identify questions addressing treatment uncertainties; therefore we excluded questions exclusively addressing diagnosis, service complaints or the natural history of epilepsy. When facilitating the meetings we encouraged each participant to consider all patient-groups and possible treatments, and offer questions on the topic. So as to maintain participation we did not attempt (during the consultation) to answer any of the questions posed, or suggest that the answers may already be known. Each participant then ranked the questions created in their meeting only, enabling us to identify the most important potential research questions.

Thematic Analysis

Using an interpretive phenomenological approach to analysis we used not only the text of the question produced but our knowledge of who asked the question and the context it was created in to better understand what was being asked. Blinded to the ranking, CH and RT grouped the questions into themes to allow us to compare professionals' and patients' questions both in content, number and relative ranking. Some sub-categories involving special groups (e.g. people with learning disability or children) were teased out from the main themes for comparison (Box 2). The themes were developed both individually and in group work until it was agreed that the identified themes were all-encompassing and useful. We did not limit the number of questions that could be posed over the course of a meeting and therefore to compare the relative rank we must adjust for the number of questions. We standardised each prioritised question as a value on a scale between 1 and 100; the lower the standardised rank score, the more important its rating. In order to test the significance of the differences between focus groups or themes, we examined the most highly ranked questions. We identified, for every participant, the number of questions from each theme ranked in the top quartile. We performed the Mann Whitney U test, using asymptotic significance, to identify differences between the focus groups, or between the themes, with statistical significance taken as p<0.05. We identified both differences between the two groups and the similarities: the shared priorities. Finally, a database of unique uncertainties was produced for publication in the UK DUETs database. [START_REF] Schmidt | Long-term effects of caffeine therapy for apnea of prematurity[END_REF] Results

The meetings produced 188 questions from 25 patients and carers and 210 questions from 17 professionals. Despite the repetition of research themes, patients and clinicians posed

Patients and carers

Patients' and carers' highest-ranked themes were: cognitive drug side-effects (mean standardised rank 13.3, n=5); managing the consequences of any side-effect from an AED (25.7, n=5); improving public awareness about the treatment of epilepsy and seizures through services (26.2, n=8) and non-medical treatment of cognitive problems (28.1, n=2). Patients rated information-based management (such as improving public awareness) a consistently higher priority than did clinicians (p=0.001).

Clinicians

The highest-ranked uncertainties concerned the following themes: individual differences in the treatment of non-epileptic attack disorder (mean rank 10.2, number of questions=3); antiepileptic drugs (AEDs) side effects; AEDs exposure in utero (11.5, n=3); prescribing in pregnancy (14.2, n=50; treatment of depression in epilepsy (17.8, n=3) and AED mood side effects (19.1, n=5). Box 4 illustrates key questions from the themes. Clinicians rated Box 3. Highest ranked research questions Both groups prioritised practical uncertainties affecting the greatest number of people ahead of esoteric questions or single issue, minority group uncertainties.

Patients and carers

"Should you take a forgotten dose as soon as you remember or skip a dose and take your next dose as normal? "What training should teachers and school nurses have about epilepsy and treatment of seizures?" Clinicians "What are the neuro-developmental effects of exposure to each of the AEDs in pregnancy?" "How is the choice of second monotherapy influenced by the seizure type/syndrome?" prescribing uncertainties (including for older people, children and in pregnancy) as more important than patients did (p<0.0001). In contrast AED side-effects were more important to patients and carers (p<0.0001). Improving public awareness about the treatment of epilepsy and seizures through services "Would rapid access to epilepsy specialists improve treatment for people with epilepsy?" Clinicians Considering individual differences in the treatment of non epileptic attack disorder "What is the best treatment programme for non-epileptic attacks?"

Individual differences in the treatment of depression in epilepsy

"What is the optimal support for those with depression and epilepsy?"

Shared priorities

Cognitive drug side effects Patients -"Do different epilepsy medications affect people differently? Are the problems reversible?" Clinicians -"Are certain people more likely to develop cognitive side effects and can they be predicted?"

Improving epilepsy control by improving public awareness of epilepsy

Patients -"What advice should be given to all schools about epilepsy and how would this improve epilepsy control for school children?" Clinicians -"Can better education about epilepsy improve quality of life for people with epilepsy by reducing stigma?"

Shared priorities

There was a great deal of consensus between the groups concerning the themes that were important to both. The most important shared priority was research into the cognitive sideeffects of AEDs. Five of the top 12 shared priorities concerned AED side-effects, two pregnancy priorities and two mood disorders uncertainties. Themes that dealt with starting AEDs were more of a priority than AED withdrawal (p<0.001).

Discussion

This study demonstrates that patients and clinicians have different agendas when asked independently to produce and prioritise lists of treatment uncertainties. We recognise some limitations including that the presence of a doctor at the three patient meetings may have introduced an observer bias and that there were no newly-diagnosed patients in those groups. The uncertainties generated by our participants are certainly not exhaustive, in part because we concentrated on treatment rather than natural history, causation and investigation. Our list of epilepsy therapeutic uncertainties needs to be supplemented by 'fresh' prospectively gleaned uncertainties by scouring recent Cochrane and other systematic reviews, and clinical guidelines. Furthermore, the database, no matter how dynamic, is redundant if we do not attempt to confirm whether the questions posed (by both clinicians and patients) are genuine uncertainties, i.e. 'known unknowns'. The first sixty questions have been scrutinised via systematic review and the outcomes published on the DUETs website of NHS Evidence: the majority have remained uncertainties following review.

[8] This project provides the framework and content which can be used by professionals in targeting genuinely patient-focussed research and we welcome validation of these results from other cohorts and geographical areas.

Practical considerations

We might have expected patients to focus more on their individual needs regarding epilepsy treatment; however the qualitative and statistical analysis does not generally support this. Not only did epilepsy professionals produce an equal number of questions under the theme of "considering the patient as an individual" (n=14) but they ranked these uncertainties as more important than patients did. Both groups prioritised practical considerations that were specific to them.

Fifteen questions produced exclusively by patients and carers focused on how to take prescribed medication, (theme 'how best to take AEDS' Box 2). Four questions were raised about the general practitioner's role in epilepsy: all came from patients and carers, including two questions about repeat prescription access. Strikingly, not only did patients and carers generate 8 of the 9 questions regarding public awareness of epilepsy and seizures, but three of these questions were in the patients and carers' top quartile.

Clinicians also prioritised practical considerations from their viewpoint, all of which clustered around 'the challenging consultation'. Clinicians posed all the questions about treatment of non-epileptic attack disorder (NEAD) (n=6, 2 were highly rated). Clinicians also accorded side effects in utero and prescribing issues in pregnancy greater importance than patients and carers did. However, half of the patients were 45 years or older and as a result may not have rated prescribing in pregnancy as a priority. Patients and carers did not volunteer any of the questions about prevention of sudden unexpected death in epilepsy (SUDEP) (n=3); clinicians produced all ten questions focussing on older people's needs (6 regarding prescribing AEDs, 4 focussing on more general therapeutic needs); clinicians asked most of questions on the considerations before starting treatment (8/9), medication adherence (10/11) and nutritional support (11/12).

Priorities

When discussing uncertainties about epilepsy treatment, we expected to receive questions about 'curing epilepsy' and achieving life-long seizure freedom: such questions were conspicuous by their absence. Patients asked two questions and epilepsy professionals eleven, regarding how best to manage seizure freedom -most of these questions were about safe drug withdrawal. Does this mirror pragmatism (as opposed to idealism) represented in the important priorities? Epilepsy is not necessarily life-long -several participants had achieved seizure freedom, both with surgery and medication.

We are still at an early stage in promoting an environment which engenders genuine patient involvement in posing questions and developing outcomes that matter [START_REF] Firkins | The problem in setting research priorities: a layman's experience[END_REF], and in mapping mismatches between researchers' and patients' priorities. For patients with rheumatoid arthritis, the priority treatment outcome is not pain reduction, but control of fatigue and sleep quality. [START_REF] Carr | Rheumatology outcomes: the patient's perspective[END_REF][START_REF] Tallon | Relation between agendas of the research community and the research consumer[END_REF][START_REF] Hewlett | Patients and professionals as research partners: challenges, practicalities, and benefits[END_REF][START_REF] Kirwan | Incorporating the patient perspective into outcome assessment in rheumatoid arthritis progress at OMERACT 7[END_REF] The James Lind Alliance has identified patient research uncertainties in several other conditions including schizophrenia [START_REF] Lloyd | Identifying uncertainties about the effects of treatments for schizophrenia[END_REF] and urinary incontinence. [START_REF] Buckley | Working together to identify research questions[END_REF] A key theme from their priority setting partnership for incontinence mirrors the practical considerations of people with epilepsy: people with continence difficulties want more public toilets.

Conclusion

We encourage researchers in other disciplines to engage with patients and carers to help people with a personal experience of a condition to express their research priorities and condition-specific uncertainties. We would welcome any group keen to address an epilepsy uncertainty or to undertake a systematic review to consult DUETs. We will need the help of the epilepsy community in both continuously updating the uncertainty database and answering the questions that are raised. 'Uncertainties' is an occasional BMJ feature [START_REF] Chadwick | What is the optimal management of partial epilepsy uncontrolled by a first choice anticonvulsant?[END_REF][START_REF] Chalmers | Confronting therapeutic ignorance[END_REF] that is supported by editors of BMJ Knowledge, BMJ Clinical Evidence, and BMJ Point of Care. We would like to encourage authors and editors to consider explicitly the uncertainties apparent in a body of work, in addition to the areas that they directly address.

What is already known on this topic?

Patients are seldom asked to identify important research questions; surprisingly neither are health care professionals. Failure to identify areas where current knowledge is deficient-'uncertainties'-can have serious negative effects on patient care.

What this study adds

The epilepsy research agenda has not been prioritised in this way before. This study identifies research topics that are highly valued by both patients and clinicians.

any other BMJPGL products to exploit all subsidiary rights, as set out in our licence (http://jnnp .bmjjournals.com/ifora/licence.pdf).

  Choice and pre-surgical considerations Uncertainties following surgery Non-drug treatments of epilepsy that are supervised by a professional Nutritional support Considering the patient as an individual Special groups -Pregnancy, older people, learning disability Non epileptic attack disorder The effect of lifestyle on seizures Drugs, alcohol and diet Complementary therapies and stress management Epilepsy co-morbidities Depression, cognitive problems and sudden unexplained death in epilepsy Information based epilepsy management Patient centred-services Public awareness of seizure management only eleven identical questions. Box 3 shows the top two prioritised questions from each group.

Box 4 .

 4 Example questions from key themesPatients and CarersManaging the consequences of any AED side effect "How frequently should we test or look for side effects of AEDs?"

Table 1 .

 1 Top 12 shared priorities. MSR -Mean Standardised ratio -the smaller the number the more important the theme, Clinicians' questions -number of questi ons in this theme produced from clinicians' meetings, Top quartile -number of questions about that theme whi ch are ranked in the top quartil e Patients' questions -number of questions in this theme from patients and carers.

	Shared prioritisation	MSR	Clinicians' questions	Clinicians -top quartile	Patients' questions	Patients -top quartile
	Cognitive drug side effects Public awareness Mood side effects Prescribing in pregnancy	21.4 25.4 26.3 27.3	4 1 5 5	3 0 3 4	5 8 1 2	4 3 0 0
	Treatment of depression as a co-morbidity Drug withdrawal Adherence In utero side effects	30.1 34.1 35.2 35.9	3 10 10 3	2 2 0 2	2 1 2 6	1 0 0 2
	Information and self-management	36.2	3	0	3	1
	Recognition and acknowledgment of side effects Management of side effects Pre-surgical choices	37.8 37.9 38.3	3 3 10	1 0 4	9 5 4	2 4 2

Acknowledgements

This was made possible by a grant, 'The Database of Uncertainties about the Effects of treatment (DUETs) for schizophrenia and epilepsy' received from the Wales Office of Research and Development (WORD). We are grateful for the members of the WERN healthclinicians' and patients' research and development groups for giving up their time to assist in this project. We also want to thank Sir Iain Chalmers, Mark Fenton and Naomi Thomas for their editorial assistance in the production of this paper.

Practical questions are prioritised by people with epilepsy suggesting that simple pragmatic projects would most closely meet their needs.

Ethics

This study involves patients and professionals as partners in a consultancy about research and as such no one is considered a participant in research. [18] Conflicts of interest All authors declare that the answer to the questions on your competing interest form are all 'no' and therefore have nothing to declare.

Copyright

The Corresponding Author has the right to grant on behalf of all authors and does grant on behalf of all authors, an exclusive licence (or non exclusive for government employees) on a worldwide basis to the BMJ Publishing Group Ltd and its Licensees to permit this article (if accepted) to be published in the Journal of Neurology, Neurosurgery & Psychiatry editions and


PHD, FRCP Nin Ps Bajaj
email: nin.bajaj@nuh.nhs.uk

Vamsi Gontu

MRCP James Birchall

FRCR James Patterson

PhD Donald G Grosset

MD Andrew J Lees

Dr Consultant Bajaj

Neurologist

Accuracy of clinical diagnosis in tremulous parkinsonian patients: a blinded video study

Keywords: Dystonia, Parkinson's disease, Tremor, Dystonic Tremor, Clinical Diagnosis

This study examines the clinical accuracy of movement disorder specialists in distinguishing tremor dominant Parkinson's disease (TDPD) from other tremulous movement disorders by the use of standardised patient videos. Two movement disorder specialists were asked to distinguish TDPD from patients with atypical tremor and dystonic tremor, who had no evidence of presynaptic dopaminergic deficit (subjects without evidence of dopaminergic deficit or SWEDDs) according to 123 I-N-ω-fluoro-propyl-2ß-carbomethoxy-3ß-(4-iodophenyl) nortropane ([ 123 I] FP-CIT) SPECT, by 'blinded' video analysis in 38 patients. A diagnosis of Parkinsonism was made if the step 1 criteria of the Queen Square Brain Bank criteria for Parkinson's disease were fulfilled. The reviewer diagnosis was compared to the working clinical diagnosis drawn from the medical history, SPECT scan result, long term follow-up and in some cases the known response to dopaminergic medications. This comparison allowed a calculation for false positive and false negative rate of diagnosis of PD.

We found a high false positive (17.4 to 26.1%) and negative rate (6.7 to 20%) for the diagnosis of PD. The diagnostic distinction of TDPD from dystonic tremor was reduced by the presence of dystonic features in treated and untreated PD patients.

Clinical distinction of TDPD from atypical tremor, monosymptomatic rest tremor, and dystonic tremor can be difficult, due to the presence of parkinsonian features in tremulous SWEDD patients. The diagnosis of bradykinesia was particularly challenging. This study highlights the difficulty of differentiation of some cases of SWEDD from PD.

Introduction

Clinico-pathological correlations have improved the diagnostic accuracy of Parkinson's disease (PD); in tertiary referral movement disorder clinics there is close to 100% concordance between the final clinical diagnosis and pathological findings. [START_REF] Hughes | Accuracy of clinical diagnosis of idiopathic Parkinson's disease: a clinico-pathological study of 100 cases[END_REF][START_REF] Hughes | The accuracy of diagnosis of parkinsonian syndromes in a specialist movement disorder service[END_REF] Nonetheless patients with tremor dominant Parkinson's disease (TDPD) continue to be a diagnostic challenge and are under-represented in published post-mortem studies.

In a community based study in Wales, [START_REF] Meara | Accuracy of diagnosis in patients with presumed Parkinson's disease[END_REF] only 53% of patients, treated with anti-parkinson therapy in primary care, met the Queen Square Brain Bank criteria (QSBBC) for the clinical diagnosis of PD when re-examined by an experienced movement disorder specialist. A quarter of the cases had no signs of parkinsonism and half of these were considered to have essential tremor (ET).

It is likely that a significant proportion of the 4-15% of de novo patients recruited for recent clinical trials with anti-parkinsonian drugs who have no evidence of nigrostriatal dopamine denervation on functional imaging (subjects without evidence of dopaminergic deficit or SWEDDS) have tremulous syndromes other than PD. This is supported by long term follow up showing minimal clinical deterioration, no response to dopaminergic therapy and in some cases no evidence on repeat functional imaging of dopamine denervation. [START_REF] Marek | Long-term follow-up of patients with scans without evidence of dopaminergic deficit (SWEDD) in the ELLDOPA study[END_REF][START_REF] Marshall | Two-year follow-up in 150 consecutive cases with normal dopamine transporter imaging[END_REF] In this study, the clinical features of patients with tremor and parkinsonism were assessed by two blinded movement disorder specialists (DGG and AJL).

The diagnosis arrived at by this process was compared in each case with the working clinical diagnosis (derived in all cases from history and examination by a third movement disorder expert [NB], long term follow up and [ 123 I] the FP-CIT result).

Methods

Participants and On-site Diagnosis

A consecutive group of patients with clinically uncertain Parkinson's disease were prospectively recruited from the neurology clinics in Nottingham and Derby (local ethics approval 07/Q2502/1). Patients were referred from both primary care (75%) and secondary (25%) care. Study inclusion was based on clinical diagnostic uncertainty, including the presence of prominent postural tremor, or focal, multifocal or segmental dystonia. Patients exposed to dopamine receptor antagonists or toxins such as manganese or carbon monoxide were excluded. Cases considered psychogenic, or with uncommon secondary or atypical causes of parkinsonism (e.g. Huntington's disease, fragile X ataxia syndrome) were also excluded. [START_REF] Ceravolo | Dopamine transporter imaging study in parkinsonism occurring in fragile X premutation carriers[END_REF][START_REF] Choi | Parkinsonism after carbon monoxide poisoning[END_REF][START_REF] Fitzgerald | Lower body parkinsonism: evidence for vascular etiology[END_REF][START_REF] Gaig | 123I-Ioflupane SPECT in the diagnosis of suspected psychogenic Parkinsonism[END_REF][START_REF] Lorberboym | 123I]-FP/CIT SPECT imaging for distinguishing drug-induced parkinsonism from Parkinson's disease[END_REF][START_REF] Olanow | Manganese-induced parkinsonism and Parkinson's disease[END_REF][START_REF] Reuter | Late onset levodopa responsive Huntington's disease with minimal chorea masquerading as Parkinson plus syndrome[END_REF][START_REF] Salvati | Parkinsonian syndrome in a patient with a pterional meningioma: case report and review of the literature[END_REF] Neurological examination was repeated after an average of 3 years of follow up, and structural imaging used selectively to exclude causative cerebral lesions (e.g. supratentorial meningioma, extensive cerebrovascular disease)(MR/CT brain imaging conducted in 15/38 cases).

The patients were collected over a three year period and referred for [ 123 I] FP-CIT scan in accordance with NICE (National Institute for Health and Clinical Excellence) guidelines. [START_REF] Stewart | NICE guideline for Parkinson's disease[END_REF] All patients gave written informed consent for use of their video material for research and teaching.

All patients were examined by one of the authors (NB) and a final diagnosis of PD, dystonic tremor, atypical tremor, monosymptomatic rest tremor or ET made. This was designated the working clinical diagnosis. All patients with a working clinical diagnosis of PD were treated with L-dopa and/or dopamine agonist drugs over the three year follow-up period. In addition, a minority of patients who were subsequently re-classified as non-PD, had had a trial of dopaminergic therapy prior to initial referral (9 of 23 cases, 39%).

Blinded Reviewer Diagnosis

Video recording of all patients was performed according to standard criteria for the Unified Parkinson's Disease Rating Scale (UPDRS) part III (motor score) and to demonstrate the features of essential tremor and dystonic tremor according to consensus criteria. [START_REF] Deuschl | Consensus statement of the Movement Disorder Society on Tremor. Ad Hoc Scientific Committee[END_REF] At the time the videos were taken, no non-PD patient was on dopaminergic therapy. The minority of PD patients on dopaminergic therapy at the time of the video were excluded from final analysis of false-negative patients with PD, in case treatment masked their clinical features.

Two movement disorder specialists (AJL and DGG) were asked to suggest the likely clinical diagnosis based on video footage. Their diagnoses took into account the QSBB operational criteria for the diagnosis of PD (with the exception of rigidity), the consensus criteria for essential tremor and clinical features suggestive of dystonic tremor. [START_REF] Deuschl | Consensus statement of the Movement Disorder Society on Tremor. Ad Hoc Scientific Committee[END_REF][16] [START_REF] Schneider | Patients with adult-onset dystonic tremor resembling parkinsonian tremor have scans without evidence of dopaminergic deficit (SWEDDs)[END_REF] The term dystonic tremor is used in this paper to embrace both "dystonic tremor" and "tremor associated with dystonia" as defined previously. [START_REF] Deuschl | Consensus statement of the Movement Disorder Society on Tremor. Ad Hoc Scientific Committee[END_REF][START_REF] Munchau | Arm tremor in cervical dystonia differs from essential tremor and can be classified by onset age and spread of symptoms[END_REF] The abnormalities observed on sequential movement testing were broadly divided into bradykinesia typical of PD (slowness with motor decrement) or atypical of PD (pure slowness, slowness with delay in initiation of fine finger/hand movements or slowness with reduced amplitude of fine finger/hand movements without decrement). The term flurry or flurries were used to describe the rapid change in tremor amplitude and frequency that is a common feature of dystonic tremor. [START_REF] Schneider | Patients with adult-onset dystonic tremor resembling parkinsonian tremor have scans without evidence of dopaminergic deficit (SWEDDs)[END_REF][START_REF] Sheehy | Writers' cramp-a focal dystonia[END_REF][START_REF] Micheli | Variable onset of adult inherited focal dystonia: a problem for genetic studies[END_REF] Since re-emergence of postural tremor is sometimes considered to be the postural representation of rest tremor in PD, the time to emergence of postural tremor was calculated visually by both reviewers for all 38 cases. [START_REF] Jankovic | Re-emergent tremor of Parkinson's disease[END_REF] Imaging Analysis [ 123 I] FP-CIT imaging was carried out according to standard protocols with discontinuation of agents that might interfere with [ 123 I] FP-CIT striatal uptake at least 4 weeks before the scan. Thyroid blocking and single slow intravenous injections of [ 123 I] FP-CIT were administered at activities between 111 and 185 MBq. Images were acquired 3-6 hours after injection using a multi-headed gamma camera.

All [ 123 I] FP-CIT scans were scored in routine clinical service, and then independently by a second nuclear medicine specialist blind to both clinical information and video footage (JP). Visual assessment graded scans as normal or abnormal (scale 0-3). [START_REF] Catafau | DaTSCAN Clinically Uncertain Parkinsonian Syndromes Study Group. Impact of dopamine transporter SPECT using 123I-Ioflupane on diagnosis and management of patients with clinically uncertain Parkinsonian syndromes[END_REF]

Statistical Analysis

We ascertained inter-reviewer agreement on video diagnosis using Cohen's kappa coefficient for each pair of blinded reviewer diagnoses per video case.

The blinded reviewer diagnoses based on video were also compared with the working clinical diagnoses. This allowed calculation of a false positive and negative rate with respect to the diagnosis of PD for the two movement disorder experts by standard formulae. The clinical and imaging data were then shared with the blinded experts.

Results

Blinded second read of [ 123 I] FP-CIT SPECT

The second read of all 38 FP-CIT SPECT scans of patients (JP) showed full concordance in abnormal versus normal with the initial read of scans by the local nuclear medicine specialist (JB). Of the fifteen abnormal scans, there was agreement on the grade of abnormality in 8 and disagreement in 7 (table 1). The scale of disagreement was never more than one point. Only two of these 6 cases of disagreement of scale featured in the false negative cases (tables 3b and 4b). Scan reports in all cases showed congruence in the most affected side on the FP-CIT scan and the clinically most affected side.

Working clinical diagnosis

In the case of TDPD patients, the working clinical diagnosis was based on clinical observation for an average of 39.6 months (SD 20.7), as well as review of video recordings (9 were recorded an average of 13.9 months after the FP-CIT scan and in 6 others, an average of 8.3 months before the FP-CIT scan); the L-dopa/dopamine agonist response and in all cases FP-CIT scan evidence of dopaminergic deficit.

Similarly, the working clinical diagnosis for clinically uncertain PD patients was based on a normal FP-CIT scan and clinical observation for an average of 35.9 months (SD 19.3); videos were taken an average of 8.8 months after the scan in 12 cases and in 11 cases an average of 5.1 months before the FP-CIT scan. In addition, a minority of patients had a trial of dopaminergic therapy (9 of 23 cases, 39%).

Blinded reviewers' diagnosis

The blinded baseline diagnosis on video assessment for each of the 38 cases for reviewers 1 and 2 is listed in table 1 Reviewer 2; Grades 0-3 for FP-CIT. [START_REF] Catafau | DaTSCAN Clinically Uncertain Parkinsonian Syndromes Study Group. Impact of dopamine transporter SPECT using 123I-Ioflupane on diagnosis and management of patients with clinically uncertain Parkinsonian syndromes[END_REF]; JP and JB refer to nuclear physicians across the two sites.

Comparison of reviewers' diagnoses with the working clinical diagnosis

There were differences in sensitivity and specificity of the blinded diagnosis based on video assessment between the two reviewers (Table 2). Reviewer 2 had a higher sensitivity for detecting PD, with an associated lower specificity, compared to reviewer 1. Considering the false negative cases on dopaminergic therapy, case 34 was the only case falsely diagnosed by both reviewers. Case 34 was felt by reviewer 1 to have flurries of tremor and no bradykinesia and by reviewer 2 to have no bradykinesia.

Bradykinesia

Summarising the findings of reviewer 1, 12 cases were considered to have true bradykinesia. Of these 12 cases, only 8 had presynaptic dopaminergic deficit on FP-CIT SPECT. For reviewer 2, 21 cases were considered to have true bradykinesia, of which only 10 had FP-CIT scans indicating presynaptic dopaminergic deficit. A total of 3 cases with normal FP-CIT scan were rated as having true bradykinesia by both reviewers. True parkinsonian bradykinesia was therefore represented in both patients with normal and abnormal FP-CIT scans.

Slowness of a non-PD type is reported in dystonic tremor. [START_REF] Schneider | Patients with adult-onset dystonic tremor resembling parkinsonian tremor have scans without evidence of dopaminergic deficit (SWEDDs)[END_REF] Of the non-PD bradykinesia types in this series, only pure slowness without fatiguing or reduced amplitude of movement was discriminating for patients with normal FP-CIT scan.

Re-emergent tremor

The average latency to postural tremor across the two blinded reviewers for the 23 SWEDD patients was 0.82s (median 0s, interquartile range 0-2s) and for the 15 TDPD cases the latency was 0.79s (median 0s, interquartile range 0-0.5s)(p = 0.69 Mann-Whitney U Test). There was no significant difference in latency between SWEDD and TDPD cases for re-emergent tremor.

Inter-blinded reviewer agreement on video diagnosis

The inter-blinded reviewer agreement on video diagnosis (PD or non-PD) was low (Kappa coefficient = 0.24 95%CI = 0, 0.48).

Discussion

The patients with suspected Parkinsonism used in this study were divided into those with normal (scans without evidence of dopaminergic deficit; SWEDDs) or abnormal presynaptic dopamine activity. Although supra-nigral forms of Parkinsonism can have a normal FP-CIT scan, few of these have rest tremor as the predominant feature and the differential diagnosis for the SWEDDs in this study lay mainly between dystonic tremor, ET and atypical tremor.

Of the other diagnoses proffered by the reviewers, monosymptomatic rest tremor is considered by many authorities as a forme fruste of PD and may have abnormal presynaptic dopaminergic imaging whilst cases labelled as 'atypical tremor' have also in some instances been associated with an abnormal FP-CIT scan. [START_REF] Ghaemi | Monosymptomatic resting tremor and Parkinson's disease: a multitracer positron emission tomographic study[END_REF][START_REF] Ceravolo | Predictive value of nigrostriatal dysfunction in isolated tremor: a clinical and SPECT study[END_REF] It remains possible that some of our cases were wrongly categorised by FP-CIT SPECT, rather than clinically mis-interpreted. We consider this unlikely given the 3 year follow up and known sensitivity of FP-CIT SPECT in early PD, and the 100% concordance in distinguishing normal from abnormal imaging results between the two scan assessors. [START_REF] Benamer | Prospective study of presynaptic dopaminergic imaging in patients with mild parkinsonism and tremor disorders: part 1. Baseline and 3-month observations[END_REF] Video diagnoses in movement disorder patients are constrained by the absence of 'hands-on' testing of rigidity and the subliminal observation of spontaneous movement and body language in real life situations rather than the recording studio. Sometimes several consultations over a number of months may be necessary before a diagnosis can be made with reasonable certainty and historical information may also be a useful distinguishing feature in the differentiation of some patients (e.g. presence of rapid eye movement sleep behavioural disorder or anosmia/hyposmia in PD). Nevertheless both reviewers had identical video material to review, and the findings allow a comparison with studies where similar methods have been used. [START_REF] Louis | Diagnosing Parkinson's disease using videotaped neurological examinations: validity and factors that contribute to incorrect diagnoses[END_REF] This study focussed on the ability of two blinded movement disorder experts to distinguish PD from SWEDDs without the availability of historical details on the patients, and as such tested the capability of step 1 of the QSBCC to distinguish PD from other tremulous disorders. Information on rigidity was unavailable to the video reviewers but increased tone is also a common associated feature of dystonic tremor and Froment's manoeuvre can also elicit cogwheel rigidity in essential tremor. [START_REF] Schneider | Patients with adult-onset dystonic tremor resembling parkinsonian tremor have scans without evidence of dopaminergic deficit (SWEDDs)[END_REF][START_REF] Sheehy | Writers' cramp-a focal dystonia[END_REF][START_REF] Micheli | Variable onset of adult inherited focal dystonia: a problem for genetic studies[END_REF][START_REF] Broussolle | Contribution of Jules Froment to the study of parkinsonian rigidity[END_REF] SPECT imaging of presynaptic dopaminergic pathways have an error rate of around 5% and perhaps greater depending on the expertise of the scanning centre. [START_REF] Jennings | 123I) beta-CIT and single-photon emission computed tomographic imaging vs clinical evaluation in Parkinsonian syndrome: unmasking an early diagnosis[END_REF] The diagnostic difficulties in this group of patients are highlighted by the range in sensitivity (72.3-93.3%) and specificity (79.3-85.2%) for the two reviewers, which can be compared with the proportion of SWEDD patients seen in clinical trials which found that 4 to 15% of patients entered as having PD had normal pre-synaptic dopaminergic imaging (although not all of the patients in those studies had a predominantly tremulous presentation). [4, 29,30,] Comparison can also be made with the high error rate in the diagnosis of tremor patients where up to 37% of ET patients were mis-diagnosed as PD (15%) or dystonia (8%). [START_REF] Jain | Common misdiagnosis of a common neurological disorder: how are we misdiagnosing essential tremor?[END_REF]

Analysis of False Negative and Positive Cases

Analysis of the false negative observations is complicated given 6 of 10 patients were on dopaminergic therapy, allowing potential masking of clinical features of PD. This may explain the inability of the examiners to detect bradykinesia but fails to fully explain the examiners' conclusions given that there was only one false negative case shared by the two reviewers.

The difference in diagnosis between the two reviewers is one of the most striking features of the present study (Kappa coefficient = 0.24 95%CI = 0, 0.48). Such variability in clinical opinion is however consistent with studies of inter-rater reliability of Parkinson's disease. [START_REF] Richards | Interrater reliability of the Unified Parkinson's Disease Rating Scale motor examination[END_REF] Analysis of the false positive cases in this study shows that interpretation of sequential finger movement testing is the largest contributor to diagnostic error. Despite careful grading of motor slowness, fully-defined bradykinesia (including decremental delay) was observed in 4 SWEDD cases by reviewer 1 and in 11 SWEDD cases by reviewer 2. Possible explanations for this finding could be that bradykinesia occurs in SWEDD patients, despite the absence of substantia nigra pathology or that motor flurries interrupt normal self-paced movement and confound the interpretation. [START_REF] Schneider | Patients with adult-onset dystonic tremor resembling parkinsonian tremor have scans without evidence of dopaminergic deficit (SWEDDs)[END_REF] Motor disturbances reminiscent of bradykinesia from the clinical descriptions have also been reported in dystonic tremor . [START_REF] Schneider | Patients with adult-onset dystonic tremor resembling parkinsonian tremor have scans without evidence of dopaminergic deficit (SWEDDs)[END_REF] Furthermore, of 30 patients with torticollis reported in 1976, 26 had tremor which was familial in 16, and parkinsonian features were present in 10 including masked facies, bradykinesia and rigidity.

Three patients had clinical signs sufficient to entertain a diagnosis of PD. [START_REF] Couch | Dystonia and tremor in spasmodic torticollis[END_REF]

On the latency of postural tremor in TDPD cases in this series

Re-emergence of postural tremor is felt by some authors to be the postural representation of rest tremor in PD. The latency of the postural or re-emergent tremor in TDPD cases in the current series was not significantly different from the SWEDD cases, which contrasts with a report of a significantly longer latency of postural tremor in PD. [START_REF] Jankovic | Re-emergent tremor of Parkinson's disease[END_REF] However, another study on ET concluded that, "clinically and electrophysiologically the postural tremors of ET and PD are indistinguishable". [START_REF] Brooks | Isolated tremor and disruption of the nigrostriatal dopaminergic system: an 18F-dopa PET study[END_REF] Further analysis of larger TDPD cohorts would be worthwhile to validate whether long latency to postural tremor in PD is a differentiating feature from the postural tremor of ET.

Dystonic Features in TDPD patients

It is apparent from this study that a number of false negative cases of untreated PD were felt by the reviewers to have dystonic clinical features such as thumb hyperextension, torticollis or flurries. Retrospective review suggests that isolated thumb hyperextension without associated 'dinner forking' or other dystonic features may be an unreliable sign.

The specificity of clinical features that suggest dystonic tremor may therefore require further consideration. [START_REF] Schneider | Patients with adult-onset dystonic tremor resembling parkinsonian tremor have scans without evidence of dopaminergic deficit (SWEDDs)[END_REF] The combination of dystonia and parkinsonism in autosomal recessive parkinsonism and young onset PD is well established. [START_REF] Bonifati | Early-onset parkinsonism associated with PINK1 mutations: frequency, genotypes, and phenotypes[END_REF][START_REF] Khan | Parkin disease: a phenotypic study of a large case series[END_REF] Focal dystonia as a feature of PD is also recognised; Lewitt reviewed 10 patients with untreated sporadic PD noting both neck and arm dystonia and dystonic features were also described in a further 9 patients with untreated PD. [START_REF] Lewitt | Dystonia in untreated parkinsonism[END_REF][START_REF] Poewe | Dystonia in Parkinson's disease: clinical and pharmacological features[END_REF]

Conclusions

The accurate diagnosis of predominantly tremulous PD in its early stages remains challenging. The use of FP-CIT SPECT in this study helped us to critically evaluate clinical decision making and to highlight the difficulties in distinguishing TDPD from dystonic tremor, atypical tremor, ET and monosymptomatic rest tremor.

Although the recognition of subtle dystonic features may help re-classify some SWEDD patients as adult dystonic tremor, dystonic features also occur in adult drug naïve PD patients.

A recent note by Bain commented on the difficulty in determining whether there was true bradykinesia in dystonic tremor patients. [START_REF] Bain | Dystonic tremor presenting as parkinsonism: long-term follow-up of SWEDDs[END_REF] We consider further motor physiological studies worthwhile to clarify the distinction between the motor abnormalities of dystonic tremor and those considered pathognomonic for parkinsonism.

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Financial Disclosure

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Conflicts of Interest

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Funding Information

Dr Bajaj was in part supported by an unrestricted investigator initiated grant from GE Healthcare.

  's Disease; DT = Dystonic Tremor; TDPD = Tremor Dominant Parkinson's Disease; ET = Essential Tremor; R1 = Reviewer 1; R2 =

Table 1 .

 1 . Clinical Diagnosis on blinded video assessment for 38 cases for Reviewer 1 and 2 versus FP-CIT result and the working clinical diagnosis.

		Blinded Video Diagnosis			Working
	Case			FP-CIT Result	Clinical
		R1	R2
					diagnosis
	1	DT	PD	Normal	DT
	2	ET	DT	Normal	DT
				Abnormal
	3	PD	PD		TDPD
				(grade 3 JP; grade 2 JB)
	4	DT	DT	Normal	DT
				Abnormal
	5	DT	PD		TDPD
				(grade 1)
	6	DT	DT	Normal	DT
	7	Monosymptomatic rest tremor DT	Normal	ET
	8	DT	DT	Normal	DT
				Abnormal
	9	PD	DT		TDPD
				(grade 1)
	10	DT	DT	Normal	DT
	11	DT	DT	Normal	ET
				Abnormal
	12	PD	PD		TDPD
				(grade 2 JP; grade 1 JB)
	13	ET	PD	Normal	DT
	14	Monosymptomatic rest tremor PD	Abnormal	TDPD

Table 2 .

 2 Diagnosis of PD in 15 patients, based on blinded video review compared to working clinical diagnosis

	Video Diagnosis
	Reviewer 1	Reviewer 2
	False Positive diagnosis
	17.4%	26.1%
	of PD

Table 3a .

 3a False positive diagnosis of PD in 4 cases on blinded video review.

	Case 23	PD	+	-	+	-Normal
	Case 30	PD	+	+	-	-Normal
	Case 32	PD/ Atypical ET	-	+	-	-Normal
	PD = Parkinson's Disease; ET = Essential Tremor; DT= Dystonic Tremor; FB
	= Fatiguable bradykinesia; FH = Facial hypomimia; RAS = reduced arm
	swing; GI = Gait impairment; RT = rest tremor; HV = hypophonic voice
	Reviewer 1
	False Positives	Blinded video Diagnosis	Clinical features leading to diagnosis	FP-CIT result
			FB FH RAS GI
	Case 17	PD	+	+	-	+ Normal

Table 3b .

 3b False negative diagnosis of PD in 7 cases on blinded video review.

	i LEDD= Levodopa Equivalent Daily Dose (Pramipexole daily dose x 67)
	NPRT = no pill rolling rest tremor; NFB = no fatiguable bradykinesia; MF =
	myoclonic flurries; NGI = no gait impairment; DF = dystonic features e.g.
	collis, thumb hyperextension, shoulder elevation; Congruent refers to
	predominant FP-CIT abnormality contra-lateral to most affected clinical side
	Reviewer 1
	False Negatives	Blinded video Diagnosis	Clinical features leading to diagnosis	FP-CIT Result	Drugs at time of video
			NPRT NFBMFNGI DF
			-	+ --+ Abnormal
	Case 5	DT			(grade 1)	Drug naive
					Congruent
			+	+ + --Abnormal
	Case 14	Monosymptomatic Rest Tremor			(grade 2 1 JB) JP; grade	Drug naive
					Congruent
	Case 18 Atypical Tremor	+	+ ---Abnormal (grade 2) Congruent	6 months of pramipexole (LEDD of 213mg/day) i
			_	_ _ _ + Abnormal	On L-dopa
	Case 24	DT			(grade 2)	for 3 years
					Congruent	400mg/day
			_	+ + --Abnormal	8 months of
	Case 34 Atypical Tremor			(grade 1)	L-dopa
					Congruent	(300mg/day)
			-	+ ---Abnormal
					(grade 1
	Case 35	ET			JP; grade	Drug naive
					2 JB)
					Congruent
	Case 37	ET	-	+ -+ -Abnormal 2 months of

Table 4a .

 4a False positive diagnoses of PD in 6 cases on blinded video review.

	Reviewer 2
	False	Blinded video	Clinical features leading to	FP-CIT
	Positives	Diagnosis			diagnosis			Result
			FB RT HV FH RAS GI
	Case 1	PD	+	-	-	-	-	-	Normal
	Case 13	PD	-	+	-	-	+	-	Normal
	Case 23	PD	+	-	-	-	+	-	Normal
	Case 26	PD	+	-	+	-	+	-	Normal
	Case 30	PD	+	-	-	-	-	-	Normal
	Case 38	PD	+	-	-	-	+	-	Normal
	PD = Parkinson's Disease; ET = Essential Tremor; DT= Dystonic Tremor; FB
	= Fatiguable bradykinesia; FH = Facial hypomimia; RAS = reduced arm
	swing; GI = Gait impairment; RT = rest tremor; HV = hypophonic voice

Table 4b .

 4b False negative diagnosis of PD in 3 cases on blinded video review. Reviewer 2's conclusions for case 35 were similar, that bradykinesia was not present and that there was a suggestion of retrocollis.

	normal gait in case 35.	(grade 2) NPRT NFB MF NGI DF	L-Dopa
							Congruent	300mg/day
			-	+	-		+
	Case 9	Dystonic Tremor				-		Abnormal (grade 1) Congruent	12 months on L-dopa 300mg/day
	Case 34	Dystonic tremor	-	+	-	-	-	Abnormal (grade 1) Congruent	8 months on L-dopa 300mg/day
			+	+	-	-	-	Abnormal
	Case 35	Dystonic Tremor						(grade 1 2 JB) JP; grade	Drug naive
								Congruent
	Analysis of the 10 false negative cases is complicated by the fact that 6
	Reviewer 2
	patients were on dopaminergic therapy. Within the drug naïve false negative
	Clinical features leading cases, reviewer 1 recorded slowness but no decrement in amplitude, and
	False Negatives thumb hyperextension, in case 5; no bradykinesia, flurries, and non-pill-rolling Blinded video Diagnosis to diagnosis Drugs at FP-CIT time of Result video tremor in case 14; no bradykinesia, absence of re-emergent tremor, and

NPRT = no pill rolling rest tremor; NFB = no fatiguable bradykinesia; MF = myoclonic flurries; NGI = no gait impairment; DF = dystonic features e.g. collis, thumb hyperextension, shoulder elevation; Congruent refers to predominant FP-CIT abnormality contra-lateral to most affected clinical side Analysing the false positive case errors, the clinical feature common to 8 of the 10 cases was the detection of apparent bradykinesia. Only 2 false positives were common to both reviewers (cases 23, 30).