CSF ANALYSIS CSF Formation Cerebrospinal fluid CSF is

CSF ANALYSIS

CSF Formation Cerebrospinal fluid (CSF) is the liquid that surrounds the brain & spinal cord. The brain & spinal cord are surrounded by the meninges that consist of three layers: dura matter, arachnoid & pia matter CSF flow between the arachnoid & pia matter in an area referred to as the subarachnoid space The cerebrospinal fluid is formed mainly in the choroid plexuses of the lateral, third, and fourth ventricles; some originates from the ependymal cells lining the ventricles and from the brain substance • Mechanism of formation: formation – Selective ultrafiltration of plasma – Active secretion by epithelial membranes Normal blood brain barrier (BBB) is important for the normal chemistry results of CSF

Functions of CSF 1 - Physical support & protection of the CNS from trauma. 2 - Supplying nutrients to the CNS & removal of metabolic wastes from CNS 3 - Intra-cerebral transport neuroendocrine role i. e. distribution of hypothalamic hormones within the brain.

Clinical Indications for CSF Analysis CSF is performed in cases of suspected: 1 - CNS infections (infectious meningitis & encephalitis) 2 - CNS malignancy (as malignant infiltrates as in leukemia. . etc) 3 - CNS hemorrhages (as subarachnoid hemorrhage) 4 - CNS demylineating diseases (as multiple sclerosis)

Routine Laboratory CSF Analysis Collection Lumbar puncture At interspace of vertebrate L 3 -4 or lower With complete aseptic techniques Sampling: Sampling Collected CSF sample is immediately divided into three tubes: Tube 1: Chemical Investigation (kept in freezer till performed) Tube 2: Microbiology Investigation (kept in room temperature) Tube 3: Microscopic Investigation (Cellular Counting – Differential – Cytology)

CSF Sample Collection

Normal CSF Analysis Normal Physical Examination Appearance & Color Clear , Colorless p. H 7. 4 Daily Secretion 450 -500 ml Specific Gravity 1. 006 -1. 007 Normal Microscopic Examination Lymphocytes 1 -5 /H. P. F Normal Chemical Examination Protein 15 -45 mg/dl Glucose 50 -80 mg /dl Chloride 115 -130 mmol /L Calcium 1. 0 -1. 40 mmol/L Phosphorus 0. 4 -0. 7 mmol/L Magnesium 1. 2 -1. 5 mmol/L Potassium 2. 6 -3. 0 mmol/L Normal Microbiological Examination No pathogenic microorganisms

Physical examination of CSF Normal CSF: CSF Clear & colorless Viscosity: equal to water (increased with increased proteins) Color and/or turbidity of CSF: observed only in pathological circumstances. Turbid CSF Bacteria WBCs cells or pus cells: suggestive of a CNS infection (menigitis or encephalitis) Blood : suggestive of hemorrhage: subarachnoid or artifactual traumatic tap: DIFFERNTIATE? Red & brown color : Blood Yellow colour 1 - Jaundice (bilirubin in CSF) 2 - Xanthochromia (hemoglobin breakdown pigments in CSF) Xanthochromic CSF suggests that a subarachnoid hemorrhage has recently occurred (at least within two hours prior to tapping). The yellow color is due to bilirubin generated in the CNS by the breakdown of hemoglobin released from RBC's. (so jaundice should be excluded).

Microscopic examination of CSF WBCs Normal Total WBCs count: count 1 -5 lymphocytes /HPF Normal differential WBCs Count: Count (in centrifuged cells) - 62% lymphocytes - 36% monocytes - 2% neutrophils Increased neutrophils: neutrophils bacterial meningitis Increased lymphocytes: lymphocytes aseptic and viral meningitis RBCs Normally CSF is blood free RBCs in CSF: subarachnoid hemorrhage & malignancy Artifact: traumatic tap (should be excluded) (Traumatic tap bright red color RBCS in decreasing number as the fluid is sampled)

Chemical examination of CSF In addition to the major ions, CSF contains oxygen, sugars (e. g. glucose, fructose), lactate, proteins (e. g. albumin, globulins), amino acids, urea, ammonia, glutamine, creatinine, lipids, hormones (e. g. insulin) and vitamins.

CSF Glucose - Normal CSF glucose: glucose 50 -80 mg/dl - The actual CSF glucose concentration may be: 1 - Falsely low in the presence of hypoglycemia Or 2 - Incorrectly interpreted as normal when the patient is hyperglycemic -Accordingly, CSF glucose should always be compared with a simultaneous plasma glucose that is drawn prior to lumbar puncture. Normal CSF glucose/ plasma glucose ratio is approximately 0. 6 -0. 7 (N. B. Ratio is decreased if plasma glucose is more than 500 mg/dl due to saturation of the glucose carrier system to CSF

CSF Glucose cont. Elevated CSF / plasma glucose ratio (more than 0. 7) has no CSF diagnostic significance (occurs with hyperglycemia) Decreased CSF / plasma glucose ratio (hypoglycorrhachia): 1 - CNS septic (pyogenic) infections Due to increased glycolysis by leukocytes and bacteria (with increase CSF lactate) 2 - Brain tumors due to increased metabolism of glucose by CNS 3 - TB meningitis & sarcoidosis Due to inhibition of glucose entry into the subarachnoid space N. B. in viral CNS infections, CSF glucose is usually normal

CSF Protein cont. Lumbar CSF protein: 15 - 45 mg/dl (mostly albumin) The majority of CSF protein is derived from the plasma by ultrafiltration Certain proteins arise within the intrathecal compartment: 1 - Immunoglobulins produced by CNS lymphocytes 2 - Transthyretin (produced by choroid plexus) 3 - Various structural proteins found in brain tissue

CSF Protein Decreased CSF protein: 1 - Leak of CSF from a tear in the dura due to severe trauma 2 - Otorrohea: Otorrohea leak of CSF from ear 3 - Rhinorrohea: Rhinorrohea leak of CSF from nose

CSF Protein cont. Increased CSF protein: 1 - Lysis of contaminant blood from traumatic tap 2 - Increased permeability of epithelial membrane (blood-brain barrier) in cases of: - CNS bacterial or fungal infections - Cerebral hemorrhages 2 - Increased production by CNS tissue as in cases of: - Multiple sclerosis (MS) - Subacute sclerosing panencephalitis (SSPE) 3 - Obstruction as in cases of : - Tumors or abscess

CSF Protein cont. Analysis of protein fractions: (Albumin & Ig. G) • 1 - Albumin of CSF is obtained from blood by means of blood-brain barrier (as it is produced solely by the liver) In cases of increased permeability of BBB, albumin is increased in CSF • 2 - Ig. G of CSF can be obtained: from blood (By BBB) : increase in cases of increase permeab. of BBB & by local synthesis from plasma cells within CSF (increased in cases of MS) So, it is essential to determine the source of Ig. G SEE NEXT SLIDE PLEAE !!!

CSF Protein cont. • FIRST: FIRST CHECK INTEGRITY OF BLOOD BRAIN BARRIER (BBB) BY CSF / serum albumin index calculation CSF serum albumin index = CSF albumin (mg/dl) / serum albumin (g/dl) Index less than 9 indicates intact BBB (no increased permeability of BBB) • SECOND: SECOND CSF Ig. G INDEX IS CALCULATED CSF Ig. G / Serum Ig. G CSF Ig. G index = -------------------CSF albumin / serum albumin Normal : less than 0. 7 Increased in cases of demylineating diseases of CNS as : Multiple sclerosis (MS)

CSF Immunoglobulin CSF Ig. G/Serum Ig. G CSF serum /Albumin index • • = CSF Ig. G index: Normally: < 0. 7 CSF Ig. G can arise: – from plasma cells within CSF – & from the blood through BBB ↑CSF [Ig. G] without concomitant ↑ in CSF [Alb] suggests local production of Ig. G: – multiple sclerosis (MS) – subacute sclerosing panencephalitis (SPEE)

CSF Electrophoresis: Oligoclonal Banding

CSF lactate is increased in cases of bacterial meningitis (due to increased glycolysis by bacteria & inflammatory cells)

CSF glutamine The level of CSF glutamine reflects level of ammonia in that is normally removed in the CNS by formation of glutamine (amino acid glutamate + ammonia). Glutamine synthesis helps to protect the CNS from the toxic effects of increased ammonia. Ammonia production is increase dramatically in patients with liver failure. Accordingly, CSF glutamine production is increased in cases of hepatic encephalopathy

Enzymes in the CSF lactate dehydrogenase (LDH) may be elevated in bacterial meningitis CSF adenosine deaminase (ADA) elevations can occur in tuberculous meningitis

Other Chemical Components of CSF • CSF [Calcium], [Potassium] & [Phosphates] are lower than their levels in the blood • CSF [Chloride] & [Magnesium] are higher than their levels in the blood – Abnormal CSF [Chloride] • marked in acute bacterial meningitis • slight in viral meningitis & brain tumors

Interpretations of Results of CSF Chemical Analysis Protein Glucose Bacterial Meningitis Viral Meningitis Tuberculous Meningitis Brain Tumor Increased Normal Increased Decreased Normal or slightly affected Decreased