Important note biochem

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)

CSF Glucose Normal CSF 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: leak of CSF from ear 3- 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

So, it is essential to determine the source of IgG CSF Protein cont. Analysis of protein fractions: (Albumin & IgG) 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- IgG 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 IgG

CSF Protein cont. 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: CSF IgG INDEX IS CALCULATED CSF IgG / Serum IgG CSF IgG index = --------------------------------------- CSF albumin / serum albumin Normal : less than 0.7 Increased in cases of demylineating diseases of CNS as : Multiple sclerosis (MS)

Notes taken in lec. When BBB ↓ there will be ↑ in albumin so will be Bactrial infection If there’s ↑ in immunoglobulin the disease will be in brain ↑ in lactase > Bactria If found glutamine is indicate for ammonia Protein in CSF > there’s Bactria And glutamate give false rustle in hypoglycemia Lymphocyte > viral Neutrophil > Bactria CSF Red> subarachnoid hemorrhage , tumor Yellow> bilirubin > cause it can cross BBB