Journal of Neurology, Neurosurgery, and Psychiatry 1981;44:791-795 Cerebrospinal fluid amino acid concentrations in

SUNIMARY Serial measurements have been made of the cerebrospinal fluid and plasma amino acid concentrations in 11 patients with viral meningitis and in four with tuberculous meningitis. A small increase in the concentrations of a few amino acids in cerebrospinal fluid has been found in a viral meningitis in contrast to a marked increase in most amino acids in tuberculous meningitis. The findings are compared with those found in patients with purulent meningitis and the possible causes and the diagnostic significance of these findings are discussed. In normal individuals, mechanisms exist which maintain cerebrospinal fluid (CSF) concentrations of amino acids at a much lower level than those found in plasma. ' Minor disturbances of the CSF amino acid profile have been described in various neurologi-cal diseases including epilepsy,2 Parkinsonism and Huntington's chorea.34 Marked changes have been described in patients with purulent meningitis,5 these changes resulting principally from a breakdown in the blood-CSF barrier to amino acids with lesse