AUBF CSF

• Cerebrospinal Fluid (CSF) is the third major fluid of the body, first recognized by Contugno in 1764.
• CSF is produced by the choroid plexus and reabsorbed in the arachnoid villi.
• The functions of CSF are to collect wastes, circulate nutrients, cushion and lubricate nervous tissues.
• The meninges line up the brain and spinal cord.
• The meninges consist of three layers: Dura Mater, Arachnoid, and Pia Mater.
• CSF is produced in the choroid plexuses, which are collections of ependymal cells.
• CSF flows through the subarachnoid space and is reabsorbed back into the blood capillaries in the Arachnoid granulations / Villae.
• 20 ml of fluid is produced per hour in the choroid plexuses.
• Total CSF Volume in adults is 90-150 ml and in neonates is 10-60 ml.
• CSF is collected through ventricular puncture, cisternal puncture, or spinal tap (lumbar puncture L3, L4, L5).
• The most common method of CSF collection is lumbar puncture.
• Specimens are collected in three sterile tubes: Tube 1 for Chemistry and Serology, Tube 2 for Microbiology, Tube 3 for Hematology, and Tube 4 may be used for microbiology to exclude skin contamination.
• CSF tests are done on a STAT (Latin statim – immediately) basis (Short turn-around-time).
• If not analyzed immediately, cells deteriorate with time, glucose undergoes glycolysis, and bacteria proliferate and multiply.
• If not possible, Hematology (Tube 3) should be refrigerated at 2-6 degree Celsius, Microbiology (Tube 2) should remain at room temperature, and Chemistry and Serology (Tube 1) should be frozen.
• Normal CSF is colorless and crystal clear.
• Laboratory test for Tubercular Meningitis includes AFB (+) Red staining bacilli, (+) for pellicle formation (web-like clot), and upon refrigeration of CSF, there would be pellicle formation after 12-24 hours.
• Pellicle formation in CSF is enhanced by refrigeration of the sample and appears as small fine clots seen after refrigeration of CSF for a period of 12-24 hours.
• Testing on synovial fluid is done on a STAT basis to avoid cell lysis and possible changes in the crystals.
• Tubercular Meningitis is caused by Mycobacterium tuberculosis and is characterized by increased BC count predominantly lymphocytes and monocytes, increased protein, decreased glucose, and increased lactate (>25 mg/dL).
• Microscopically, pellicle formation in CSF consists of white blood cells against a fibrinous background and must be examined for bacteria through gram stain and culture.
• Variations in clotting in CSF can include small clots, large clots, web-like clots, and clotting en masse.
• Normal CSF does not have clots due to the absence of fibrinogen.
• CSF Lactate is also increased in cases of intracranial hemorrhage and hydrocephalus.
• Increased CSF Lactate Dehydrogenase (LD) is observed in cases of Myocardial Infarction, where LD1 is predominant.
• CSF Lactate Dehydrogenase (LD) is derived from brain tissue (LD1), lymphocytes (LD2), neutrophils (LD3), and macrophages (LD4, LD5).
• Fungal meningitis is caused by Cryptococcus neoformans, which increases WBC count predominantly lymphocytes and monocytes, and has increased protein, decreased glucose, and increased lactate (>25 mg/dL).
• Increased CSF Glucose is not significant in cases of Bacterial Meningitis, which has the lowest glucose level.
• Bacterial meningitis causes increased CSF WBC, neutrophils, increased LD4 and LD5, increased protein, decreased glucose, and increased lactate (>35 mg/dL).
• The Limulus Lysate Test is a reagent that tests for bacterial endotoxin (for Gram(-) bacteria only) and is positive in cases of bacterial meningitis.
• CSF Lactate is inversely proportional to CSF glucose and increased in cases of fungal, tubercular, and bacterial meningitis.
• If LD2 is predominant in CSF, there is a neurological abnormality.
• Normal CSF Glucose is observed in cases of Viral Meningitis.
• Viral meningitis is caused by Enterovirus, which increases WBC count predominantly lymphocytes (increased LD2 and LD3), and has normal glucose and lactate.
• Viral meningitis shows normal CSF lactate.
• CSF Glutamine, a by-product of ammonia and alpha-ketoglutarate, is much more stable than ammonia and functions to remove toxic ammonia.
• Decreased CSF glucose is significant and a characteristic finding in cases of Parasitic, Fungal, Tubercular meningitis.
• If CSF of patients with multiple sclerosis will be subjected to electrophoresis, the presence of oligoclonal bands in CSF and not in serum is indicative of MS (increased IgG).
• Spindle-shaped cells may be seen with systemic malignancies.
• CSF Glucose normal value is 60-70% of blood glucose.