Glucose enters the CSF from the plasma by 2 mechanisms, diffusion and active transport. The level of CSF glucose is influenced by the concentration and duration of the plasma glucose level. CSF glucose levels are 60-70% of plasma glucose levels. The normal fasting CSF glucose is 40-70 mg/dl. In children the nonfasting reference range is 45-100 mg/dl. The CSF glucose level lags behind the plasma level by 30-90 minutes. An increase in CSF glucose means the patient was hyperglycemic 30 to 90 minutes before and has no special clinical significance. A decreased CSF glucose is seen in:
A high index of suspicion is essential to diagnose the disease because early diagnosis is the key to a satisfactory outcome. If tuberculous meningitis is seriously suspected, treatment should start immediately. Treatment involves chemotherapy to control and eradicate the infection, management of hydrocephalus and elevated intracranial pressure, and immunomodulation with corticosteroids (cortisone-like drugs such as prednisone ). The World Health Organization (WHO) recommends a two-month intensive course of isoniazid, rifampin, pyrazinamide, and ethambutol followed by 4 months of isoniazid and rifampin. Elevated intracranial pressure can be life-threatening. The hydrocephalus may require placement of a ventriculoperitoneal shunt. The use of the corticosteroid dexamethasone improves survival in patients over 14 years of age but probably does not prevent severe disability.