until csf starts to come out of the needle. once all of the csf is collected, the stylet is then reinserted before removal of the needle. interpretation 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 lumbar puncture 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), lumbar puncture 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 lumbar punctures, 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 when peripheral blood contaminates the withdrawn csf, a common procedural complication, white blood cells will be present along with erythrocytes, and their ratio will be the same as that in the peripheral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 lumbar puncture. 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 lumbar puncture 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. infection appearance wbcs / mm3 protein (g/l) glucose normal clear <5 0.15 to 0.45 > 2/3 of blood glucose bacterial yellowish, turbid > 1,000 (mostly pmns) > 1 low viral clear < 200 (mostly lymphocytes) mild increase normal or mildly low tuberculosis yellowish and viscous modest increase markedly increased decreased fungal yellowish and viscous < 50 (mostly lymphocytes) initially normal, then increased normal or mildly low history lumbar puncture, early 20th century. the first technique for accessing the dural space was described by the london physician walter essex wynter. in 1889 he developed a crude cut down with cannulation in four patients with tuberculous meningitis. the main purpose was the treatment of raised intracranial pressure rather than for diagnosis. the technique for needle lumbar puncture was then introduced by the german physician heinrich quincke, who credits wynter with the earlier discovery; he first reported his experiences at an internal medicine conference in wiesbaden, germany, in 1891. he subsequently published a book on the subject. the lumbar puncture procedure was taken to the united states by arthur h. wentworth an assistant professor at the harvard medical school, based at children's hospital. in 1893 he published a long paper on diagnosing cerebrospinal meningitis by examining spinal fluid. however, he was criticized by antivivisectionists for having obtained spinal fluid from children. he was acquitted, but, nevertheless, he was uninvited from the then forming johns hopkins school of medicine, where he would have been the first professor of pediatrics. historically lumbar punctures were also employed in the process of performing a pneumoencephalography, a nowadays obsolete x-ray imaging study of the brain that was performed extensively from the 1920s until the advent of modern non-invasive neuroimaging techniques such as mri and ct in the 1970s. during this quite painful procedure, csf was replaced with air or some other gas via the lumbar puncture in order to enhance the appearance of certain areas of the brain on plain radiographs.