CSF Examination

Presented By: Nasir Nazeer

ContentsIntroductionSample CollectionCSF Lab ExaminationChemical AnalysisSerological ExaminationOther TechniquesReferences

IntroductionCSF is the fluid surrounding the brain and spinal cord.This fluid is clear, watery liquid that protects the CNS from injury and cushions it from the surrounding bone structure.It contains variety of Substances such as Glucose, Protein, and WBCs from immune system.

HistoryCSF was 1st examined in 19th century using primitive techniques e.g. sharpened bird quills.CSF Analysis reached at its peak in 1950-60s when no workup of a significant CNS problem was performed without a lumbar Puncture.Advent of sophisticated imaging techniques particularly CT Scan and MRI, LP is no longer an important test of most intra-caranial mass lesion.LP remains a critical procedure in the diagnosis of CNS infections and Inflammatory disease.

PurposeThe purpose of CSF analysis is to diagnose medical Disorders that affect the CNS.

Viral and Bacterial Infections.Tumors of Nervous System.Syphilis, a Sexually transmitted disease.Bleeding around the brain and spinal cord.Multiple sclerosis,a disease that affects the myelin coating of the nerve fibers.Guilain-Barre syndrome,an inflammation of the nerves.

Sample Collection

The Process to remove the CSF is called as Lumber Puncture or spinal tap.In rare cases such as spinal fluid blockage in the middle of the back, doctor may perform a Spinal Tap in the neck.The Sample is drawn from the vertebrae known as the L4-5 is preferable because the spinal cord stops near L2 and the needle introduce below this level will miss the Spinal cord & encounters only nerve roots.

A lumber Puncture takes about 30 minutes.If the Patient has spinal arthritis or obese ,it may be necessary to introduce the spinal needle using x-ray guidance.In Order to get an accurate sample of CSF it is critical that a patient is in the proper position.

Sample Collection (Contd..)

During a LP the doctor drapes the back with a sterile covering.The doctor inserts a hollow thin needle in the space b/w two vertebrae of the lower back and slowly advances it towards the Spine.A steady flow of CSF normally the color of water will begin to fill the needle as soon as it enters the spine canal.The doctor measures the CSF pressure with a special instrument called a Manometer an withdraw several vials of fluid for lab analysis.

Sample Collection (Contd..)

Patients can perform their normal activities before a lumber puncture.After the procedure the doctor covers the site of the puncture with a sterile bandage.

Sample Collection (Contd..)

Sample Collection

RisksFor most people the most common side effect after the removal of CSF is headache.

10-30% of adult patients.Up to 40 % of children.

It is caused by decreased CSF pressure.A Stiff neck and nausea may accompany the headache.LP headache typically begins within 2 days after the procedure and persist for few days to several weeks.Control of Pain by Several medication containing Caffeine.

PrecautionsA LP to withdraw a Small Amount of CSF for analysis may lead to serious complications.LP should be performed with extreme cautions.People who have blood clotting or bleeding disorders LP can cause bleeding that compress the spinal cord.

CSF Lab ExaminationExamination of the CSF can provide important diagnostic information when there is reason to suspect there has been trauma or a non traumatic insult to the CNS.Disorders that can be evaluated by examination of the CNS are intracranial hemorrhage infections, sclerosis, Guillain-Barre syndrome and neurosyphilis.

AnalysisLike other body fluids, the CSF provides a sample for analysis that often reveals biochemical and cellular changes reflective of disease processes.Analysis of the cerebrospinal often provides the evidence needed by the physician to initiate appropriate treatment.

Color and appearanceNormal CSF should be clear and colorless.Any coloration or cloudiness of the CSF is considered abnormal.Colors observed include white or pearlescent, red, pink, orange and yellow.Red of pink indicates the presence of blood.

Cell countBoth leukocyte and RBC counts are performed on the CSF.Normal spinal fluid usually contain fewer than five to eight leukocytes per cubic mm (these ranges vary from lab to lab).Increase numbers of leukocytles indicate an infectious process.Increased numbers of RBC may indicate a hemorrhage or a traumatic condition.

Leukocyte-differentialThis procedure is referred to as the leukocyte or white cell differential.Most labs perform the differential while performing the cell count on the hemacytometer, differentiating on the polynuclear and mononuclear cells.Most patients with bacterial infections will demonstrate increased numbers of neutrophils while those with fungal, tubercular and viral infection will have increase numbers of lymphocytes.

Leukocyte-differential (Contd..)

The differential may also reveal other cell types that may be of interest in diagnosing certain conditions.Appearance of CSF may indicate the presence of a tumor.Plasma cells may be observed in several different disorders, including multiple sclerosis and tuberculous meningitis.

Commonly requested tests

ColorAppearanceCell CountGram StainCultureGlucose DeterminationProtein Level

Gram stain and cultureA Gram’s stain is performed on almost all cerebrospinal fluid samples.Cultures are also set up in order to retrieve and identify organisms present in the CSF.If the physician suspects a viral, mycobacterial, or rickettsia organism, it is important that special culture techniques be followed for isolation of these organisms.

Chemical analysisChemical analysis are important in helping to establish a diagnosis.The spinal fluid protein is typically about 1/100th the concentration of protein in blood. Increased CSF protein may be due to damage to the, CSF brain barrier resulting in an increased permeability, decreased removal of protein from the CSF.

Chemical analysis (Contd..)

Decreased protein levels are less commonly encountered.Common reasons are removal of large amounts of CSF and leakage of CSF caused by trauma.Glucose concentrations can be determined using the same methodologies as used for blood.The most common finding is a low glucose concentration associated with most types of CNS infections.If patient is hyperglycemic, then the CSF glucose concentrations will like wise be elevated and an infection may be masked.If the patient is hypoglycemic the physician may be misled by a low CSF glucose.

Chemical analysis (Contd..)

Lactate determination is considered to be of some use by physicians in differentiating bacterial, tuberculous and fungal meningitis from viral meningitis.The lactate concentration in viral meningitis is generally normal or low in comparison to that in bacterial, tuberculous, or fungal meningitis.Other chemical anaylses include Glutamine (an indicator of excess ammonia in the CNS), LDH, chloride, and bilirubin.

Serologic examinationSerologic examination of CSF is typically involved with diagnosis of neurosyphilis.A fluorescent treponemalantibody absorption (FTA-ABS) test for CSF has also been developed.The VENERAL DISEASE RESEARCH LAB. (VDRL) Test is also used.

Other techniquesIt is important to recognize other techniques that have been used and may still be used for CSF.Immunoelectrophorsis (CIE), latex agglutination tests for bacterial antigens, enzyme linked immunosorbent assay (ELISA) and limulus of gram-negative bacterial).The nucleic acid probes using PCR are the newest of the techniques being investigated for indentification of specific infectious agents.