Analysis of the cerebrospinal fluid generally includes a cell count and determination of the glucose and protein concentrations. The other analytical studies of cerebrospinal fluid are conducted according to the diagnostic suspicion. Pressure determination<unk>  in a child suspected of having meningitis. Increased CSF pressure can indicate congestive heart failure, cerebral edema, subarachnoid hemorrhage, hypo-osmolality resulting from hemodialysis, meningeal inflammation, purulent meningitis or tuberculous meningitis, hydrocephalus, or pseudotumor cerebri. In the setting of raised pressure (or normal pressure hydrocephalus, where the pressure is normal but there is excessive CSF),<unk>  may be therapeutic. Decreased CSF pressure can indicate complete subarachnoid blockage, leakage of spinal fluid, severe dehydration, hyperosmolality, or circulatory collapse. Significant changes in pressure during the procedure can indicate tumors or spinal blockage resulting in a large pool of CSF, or hydrocephalus associated with large volumes of CSF. Cell count The presence of white blood cells in cerebrospinal fluid is called pleocytosis. A small number of monocytes can be normal; the presence of granulocytes is always an abnormal finding. A large number of granulocytes often heralds bacterial meningitis. White cells can also indicate reaction to repeated<unk> s, reactions to prior injections of medicines or dyes, central nervous system hemorrhage, leukemia, recent epileptic seizure, or a metastatic tumor. When peripheral blood contaminates the withdrawn CSF, a common procedural complication, white blood cells will be present along with erythrocytes, and their ratio will be the same as that in the peripheral blood. The finding of erythrophagocytosis, where phagocytosed erythrocytes are observed, signifies haemorrhage into the CSF that preceded the<unk> . Therefore, when erythrocytes are detected in the CSF sample, erythrophagocytosis suggests causes other than a traumatic tap, such as intracranial haemorrhage and haemorrhagic herpetic encephalitis. In which case, further investigations are warranted, including imaging and viral culture. Microbiology CSF can be sent to the microbiology lab for various types of smears and cultures to diagnose infections. * Gram staining may demonstrate gram positive bacteria in bacterial meningitis. * Microbiological culture is the gold standard for detecting bacterial meningitis. Bacteria, fungi, and viruses can all be cultured by using different techniques. * Polymerase chain reaction (PCR) has been a great advance in the diagnosis of some types of meningitis, such as meningitis from herpesvirus and enterovirus. It has high sensitivity and specificity for many infections of the CNS, is fast, and can be done with small volumes of CSF. Even though testing is expensive, cost analyses of PCR testing in neonatal patients demonstrated savings via reduced cost of hospitalization. * Numerous antibody-mediated tests for CSF are available in some countries: these include rapid tests for antigens of common bacterial pathogens, treponemal titers for the diagnosis of neurosyphilis and Lyme disease, Coccidioides antibody, and others. * The India ink test is still used for detection of meningitis caused by Cryptococcus neoformans, but the cryptococcal antigen (CrAg) test has a higher sensitivity. Chemistry Several substances found in cerebrospinal fluid are available for diagnostic measurement. * Glucose is present in the CSF; the level is usually about 60% that in the peripheral circulation. A fingerstick or venipuncture at the time of<unk>  may therefore be performed to assess peripheral glucose levels and determine a predicted CSF glucose value. Decreased glucose levels can indicate fungal, tuberculous or pyogenic infections; lymphomas; leukemia spreading to the meninges; meningoencephalitic mumps; or hypoglycemia. A glucose level of less than one third of blood glucose levels in association with low CSF lactate levels is typical in hereditary CSF glucose transporter deficiency also known as De Vivo disease. * Increased glucose levels in the fluid can indicate diabetes, although the 60% rule still applies. * Increased levels of glutamine are often involved with hepatic encephalopathies, Reye's syndrome, hepatic coma, cirrhosis, hypercapnia and depression. * Increased levels of lactate can occur the presence of cancer of the CNS, multiple sclerosis, heritable mitochondrial disease, low blood pressure, low serum phosphorus, respiratory alkalosis, idiopathic seizures, traumatic brain injury, cerebral ischemia, brain abscess, hydrocephalus, hypocapnia or bacterial meningitis. * The enzyme lactate dehydrogenase can be measured to help distinguish meningitides of bacterial origin, which are often associated with high levels of the enzyme, from those of viral origin in which the enzyme is low or absent. * Changes in total protein content of cerebrospinal fluid can result from pathologically increased permeability of the blood-cerebrospinal fluid barrier, obstructions of CSF circulation, meningitis, neurosyphilis, brain abscesses, subarachnoid hemorrhage, polio, collagen disease or Guillain–Barré syndrome, leakage of CSF, increases in intracranial pressure, or hyperthyroidism. Very high levels of protein may indicate tuberculous meningitis or spinal block. * IgG synthetic rate is calculated from measured IgG and total protein levels; it is elevated in immune disorders such as multiple sclerosis, transverse myelitis, and neuromyelitis optica of Devic. Oligoclonal bands may be detected in CSF but not in serum, suggesting intrathecal antibody production.
Lumbar puncture
Ultrasound-guided lumbar puncture
Brain biopsy
Hemoencephalography
Cranioscopy
CSF tap test
Meningeal biopsy
Intracranial pressure monitoring