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Cerebrospinal fluid

Cerebrospinal fluid. Introduction. The cerebrospinal fluid is a modified tissue fluid. The fluid flows through the subarachnoid space located between the arachnoid and pia mater. A clear, colorless liquid that fills the ventricles (cavities) of the brain and the spinal cord.

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Cerebrospinal fluid

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  1. Cerebrospinal fluid

  2. Introduction • The cerebrospinal fluid is a modified tissue fluid. • The fluid flows through the subarachnoid space located between the arachnoid and pia mater. • A clear, colorless liquid that fills the ventricles (cavities) of the brain and the spinal cord. • CSF replaces lymph in the CNS. • The total quantity of CSF is about 150 mL in adult and and 10 to 60 mL in neonates. • Approx. 30 ml in the spinal cord. • It is formed at the rate of about 0.35 ml per min OR 20 mL hour = 500 ml per day.

  3. Functions of the CSF • The CSF is believed to be nutritive for both neurons and glial cells. • The CSF provides a medium for removing waste products of cellular metabolism form the nervous system. • The presence of a number of biologically active principles (releasing factors, hormones, neurotransmitters, metabolites) within the CSF suggests that it may function as a transport system.

  4. CSF Formation • The bulk of CSF is formed by the Choroid plexuses of lateral ventricles and lesser amount by the Choroid plexuses of third and fourth ventricles. • The circulating fluid is reabsorbed back into the blood capillaries in the arachnoid granulations (villae) at a rate equal to its production. • The cells of the arachnoid granulations act as one-way valves that respond to pressure within the central nervous system (CNS) and prevent reflux of the fluid.

  5. Lumbar Puncture • Lumbar puncture is used to obtain a sample of cerebrospinal fluid (CSF) to aid in the diagnosis or the therapeutic of various conditions. • Indications: diagnostic and Therapeutics. • THERAPEUTICS Treatment Obstructive hydrocephalus Drug administration Anesthesia Antibiotic Chemotherapy

  6. Indications • Fever of unknown origin • Children from 1 month to 3yrs having fever and vomiting. • Over age 3yrs having nuchal rigidity, Kernig’s sign, and Brudzinski’s sign • Partially treated children are less likely to be febrile or exhibit an altered mental status

  7. (animation)

  8. Cont… • LP in adults and in older children may be performed from L2 to L3 interspaces' to the L5 to S1 interspaces'. • At birth, the cord ends at the level of L3. • LP in infant may be performed at the L4 to L5 or L5 to S1 interspaces'. • Sterile gloves MUST be used. • Wash back with antiseptic solution. • Sterile towel under hips. • The skin and deeper subcutaneous tissue are infiltrated with local anesthetic.

  9. Procedure

  10. Tube 1: is used for chemical and serologic tests because these tests are least affected by blood or bacteria introduced as a result of the tap procedure. • Tube 2: is usually designated for the microbiology Laboratory. • Tube 3: is used for the cell count, because it is the least likely to contain cells introduced by the spinal tap procedure. • Tube 4: reserve tube for any special tests or for the microbiology laboratory to provide better exclusion of skin contamination or for additional serologic tests.

  11. Purpose of CSF Analysis The purpose of a CSF analysis is to diagnose medical disorders that affect the central nervous system. Some of these conditions include: • Viral and bacterial infections, such as meningitis and encephalitis . • Tumors or cancers of the nervous system. • Bleeding (hemorrhage) around the brain and spinal cord. • Multiple sclerosis: a disease that affects the myelin coating of the nerve fibers of the brain and spinal cord. • Syphilis, a sexually transmitted disease .

  12. Complications • Headache Headache After Lumbar Puncture • Most common complication • Occurs 5-30% of all spinal taps • Usually starts up to 48 hours after to procedure. • Usually lasts 1-2 days (occas 14 days) • Caused by leaking of fluid through dural puncture site. • Treatment

  13. Opening Pressure • Normal opening pressure is 90~180mmH2O in adults 10~100mmH2O in children. • In Obese pts: up to 250mmH2O can be normal

  14. CSF pressure Elevated pressure Decreased pressure Spinal-subarachnoid block Dehydration Circulatory collapse CSF leakage • Congestive heart failure • Meningitis • Cerebral edema • Mass lesion

  15. Macroscopic examination • Total volume • In adult, CSF volume is 90-150 ml. • In neonates, CSF volume is 10 -60 ml. • Production is approx. 0.35 ml/min. • Distribution • 20 ml in the ventricles. • 60 ml in the subarachnoid space. • 70 ml in the spinal canal. • Specific gravity: 1.006 – 1.008 • pH: Alkaline

  16. Appearance • Normal CSF is crystal clear and the consistency of water. The major terminology used to describe CSF appearance includes clear, cloudy or turbid, milky, xanthochromic, and bloody. • Cloudy, turbid or milky • Increased protein or lipid concentration, but it may also be indicative of infection. • May be caused by WBCs (over 200 cells/µl). • RBCs (over 400 cells/µl). • Xanthochromia is a term used to describe CSF supernatant that is pink, orange or yellow. • Pink: very slight amount of oxyhemoglobin • Orange: heavy hemolysis • Yellow: conversion of oxyhemoglobin to unconjugatedbilirubin

  17. Xanthochromic Other causes of xanthochromia include • Oxyhemoglobin: from lysed RBCs present in CSF before lumber puncture, or traumatic tap with lysis of RBCs after lumber puncture. • Bilirubin from lysed RBCs in CSF, or increased direct bilirubin with normal blood-brain barrier, or in premature infants an immature blood-CSF barrier plus elevated total bilirubin. • increased protein concentrations, and melanoma pigment. • Presence of the pigment carotene.

  18. Traumatic tap: Grossly bloody CSF can be an indication of intracranial hemorrhage (subarachnoid hemorrhage), but it may also be due to the puncture of a blood vessel during the spinal tap procedure. Three visual examinations. • We can differentiate between both by: • Uneven distribution of blood: Traumatic tap often shows significant clearing of blood between the first and third tubes. • Centrifugation: Traumatic tap often shows significant clear supernatant after centrifugation. • Clot formation: Fluid collected from traumatic tap may form clots due to the introduction of plasma fibrinogen into the specimen.

  19. Microscopic examination • CSF cell count • Normal CSF RBCs are less than 5/mm3. • Counts that are otherwise unexplained may be due to a traumatic tap. • The cell count that is routinely performed on CSF specimen is the WBC's count. • NOTE: Cell counts should be done within 30 minutes after withdrawal of the specimen to avoid cell disintegration. Specimen that can't be analyzed immediately should be refrigerated. • Normal adult CSF contains 0 to 5 WBC's /µl. the number is higher in children and as many as 30 WBC's /µl can be consider normal in newborns.

  20. Causes for increased Neutrophils • Meningitis (Bacterial meningitis, Early viral meningoencephalitis). • Reaction to repeated lumber puncture. • Injection of foreign materials in subarachnoid space. • Causes for increased Eosinophil • Parasitic infestations. • Fungal infection. • Rickettsial.

  21. Biochemical estimation

  22. Glucose • Glucose enters the CSF by selective transport across the bloodbrain barrier, • The CSF glucose concentration is slightly lower than that plasma and usually between 60 – 70 % of plasma glucose concentration. • The normal range of CSF glucose is between 50 and 80 mg/dl • The blood glucose sample is needed for comparison. • The blood glucose should be drawn about 2 hours prior to the spinal tap to allow time for equilibration between the blood and fluid. • CSF glucose is analyzed using the same procedures employed for blood glucose. Specimens should be tested immediately because glycolysis occurs rapidly in the CSF.

  23. Clinical significance • Low CSF glucose values can be of considerable diagnostic value in determining the causative agents in meningitis. • The finding of markedly decreased CSF glucose accompanied by: • An increased WBC's count and a large percentage of Neutrophil is most indicative of bacterial meningitis. • WBC's count and a large percentage of lymphocytes is most indicative of tubercular meningitis.

  24. Proteins • The most frequently performed chemical test on CSF is the protein determination. Normal CSF contains a very small amount of protein. • Normal CSF protein concentration (mg/dl) is less than 1% of serum protein concentration (g/dl) and usually listed as 15 to 45 mg/dl with slightly higher values found in infants and elderly people. • A rise in CSF protein is seen in various diseases as a result of three primary mechanisms: • Decreased clearance of normal protein from the fluid and degeneration of neural tissue. • Increased local synthesis of immunoglobulin. • Increased capillary permeability due to the blood-brain barrier damage.

  25. Clinical Significance of Elevated Protein Values • Elevated total protein values are most frequently seen in pathologic conditions. • Meningitis • Hemorrhage • Primary CNS tumors • Diabetes • Uremia • Methodology : The two most routinely used techniques for measuring total CSF protein use the principles of turbidity production or dye binding ability.

  26. CSF Lactate • Measurement of lactate concentrations in cerebrospinal fluid (CSF) may be useful as part of the investigation of inborn errors of metabolism in which lactic acidosis occurs. • This includes disorders of gluconeogenesis, pyruvate dehydrogenase complex, the Krebs cycle and the mitochondrial electron transport chain. • In bacterial, tubercular and fungal meningitis elevations of CSF lactate greater than 25mg/dl. • Destruction of tissue within the CNS owing to oxygen deprivation (hypoxia) causes the production of increased CSF lactic acid levels.

  27. Measurement of lactate in CSF has also been advocated for investigating children with unexplained neurological disease. • Levels greater than 35 mg/dL are frequently seen with bacterial meningitis, whereas in viral meningitis, lactate levels remain lower than 25 mg/dL. • CSF lactate levels remain elevated during initial treatment but fall rapidly when treatment is successful, thus offering a sensitive method for evaluating the effectiveness of antibiotic therapy.

  28. Microbiology test • Bacterial Infections • The Gram stain is of great importance, because this often dictates the initial choice of antibiotic. • Gram-negative diplococci intracellular or extracellular are indicative of Neisseria meningitidis • Small Gram-negative bacilli may include Haemophilus influenza, especially in children. • Gram-positive cocci indicates Streptococcus pneumoniae, other Streptococcus species, or Staphylococcus.

  29. Serologic testing • Serologic testing of the CSF is performed to detect the presence of neurosyphilis. However, detection of the antibodies associated with syphilis in the CSF still remains a necessary diagnostic procedure. • Serologic tests: • VDRL (Venereal Disease Research Laboratory ) • FTA –ABS (Confirmatory test )

  30. Summary

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