A patient with a several year history of
normal pressure hydrocephalus was found to have an
infection owing to Cryptococcus neoformans. Cryptococcal
infection was not suspected until typical cells were observed in a Wright's stained smear of cerebrospinal fluid (CSF). A review of past medical findings in this patient showed elevated CSF values for
lactic acid and
protein. This case prompted us to review the use of
lactic acid as an
indicator of
fungal meningitis and compare it to other more commonly used nonspecific indicators of
fungal meningitis, notably the concentrations of
glucose and
protein, and the number of leukocytes in CSF. In our institution, all 10 culturally proven cases of
fungal meningitis, for which the
lactic acid concentration in the CSF was available, were found to have an elevated
lactic acid concentration (range 3.2 to 13.3 mmol per L vs normal range 0.8 to 2.8 mmol per L). No other nonspecific
indicator was elevated in all 10 patients. In view of the poor sensitivity of stained smear or wet preparations and cultures, when less than five ml of CSF are used for culture, an elevated
lactic acid value in a patient with or without signs of
meningitis should raise the suspicion of
fungal infection.