Cerebrospinal fluid formula in patients with central nervous system infection

Knowledge of the CSF formula is clinically useful and at times critical in the analysis of a number of diagnostic problems presented by patients with CNS infections. The decision to withhold antimicrobial therapy in the patient with an acute meningitis syndrome, when viral etiology is suspected, is justified in the presence of a polymorphonuclear cellular reaction provided the CSF glucose is greater than 45 mg per dl and the protein less than 130 mg per dl. Patients who fail to improve clinically should be retapped in 8 to 12 hours. A persisting PMN reaction or the combination of a PMN pleocytosis and hypoglycorrachia virtually rules out viral infection and, in the face of negative routine cultures, requires a diligent search for focal parameningeal suppuration and consideration of CNS tuberculosis and fungal infection. Careful re-evaluation of the patient emphasizing factors such as duration of illness and potential sites of parameningeal suppuration will be useful in guiding further diagnostic studies. Head CT scanning including views of the sphenoid sinuses may be especially helpful in this regard.