Lumbar puncture is one of the earliest tests employed in neurological disorders. Lumbar puncture needle is introduced in the inter vertebral space between second and third lumbar vertebrae and cerebrospinal fluid collected. CSF is examined for its color, biochemical examination and cytology.
Before doing lumbar puncture, fundus examination be done to look for evidence of papilloedema which indicates raised intracranial tension. Lumbar puncture is contraindicated in the presence of raised intracranial tension.
By doing lumbar puncture we not only collect CSF for examination but also measure CSF pressure by manometer, use it for diagnostic purposes, introduction of drugs in cases of meningitis and air for encephalography and radio-opaque substance for myelography. CSF is also collected by cisternal and ventricular puncture.
If proper precautions have been taken it is a safe procedure. After lumbar puncture person must rest in bed for few hours. Common side effect is headache which comes after a few hours, is throbbing in character and is often associated with nausea, vomiting and pain in the neck and back.
Normal CSF is colorless, clear. Presence of blood indicates either local trauma or sub arachnoid hemorrhage especially fresh. Xanthochromia or yellowish coloration of CSF is found in cerebral hemorrhage and when pus is present in CSF in considerable amount. Turbidity when present indicates excess of polymorphonuclear cells (meningitis). A clot or cob web may form in cases of tuberculous meningitis.
Of the biochemical tests, protein content is 30- 40 mg/dl and sugar 80 mg/dl. Normal CSF contains a small number of cells mostly lymphocytes.
Excess of cells in the CSF indicate meningeal irritation. In cases of meningitis, CSF is examined for bacteria by gram’s staining. A culture examination of CSF is often carried out in suspected infective process for identifying the causal organism.
CSF examination has an important role in diagnosing bacterial and viral diseases but its role in cases of cerebral hemorrhage is now being taken over by Cl’ scan because of hazards involved.
Colloidal reactions in the form of colloidal gold reaction is of value in cases of general paralysis of insane (OPI) and differentiates it from other form of neuro-syphilis. Serological reactions like Wassermann reaction (W.R) are also of help in cases of neuro-syphilis.
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