Normal ventricular-CSF may comfound the diagnosis of tuberculous meningitis hydrocephalus.

BACKGROUND The standard procedure for the diagnosis of central nervous system (CNS) infections consists of cerebrospinal fluid (CSF) sampling, which is usually accomplished by a lumbar puncture. However, in some patients presenting with acute hydrocephalus submitted to immediate CSF drainage, the fluid is customarily obtained from the placed draining system. In addition, the CSF obtained from the ventricular and lumbar spaces in some cases may show unusual differences, both in physiological and pathological conditions. ILLUSTRATIVE CASES We report two children who presented with confounding results in the initial studies of their ventricular and lumbar CSF who were subsequently diagnosed with tuberculous meningitis, causing delay in diagnosis and treatment. AIM. By reporting these cases, we wanted to alert the treating physician about the possibility of this discrepancy to avoid the delayed diagnosis and management of the affected patients. DISCUSSION We comment on the possible pathophysiological mechanisms that may result in this dissociation in ventricular and lumbar CSF composition. CONCLUSIONS; Normal results in CSF studies, especially those of the ventricular fluid, do not always rule out the presence of tuberculous meningitis. We suggest obtaining a CSF sample from the lumbar subarachnoid space in doubtful, or suspicious, cases of CNS infection even in the presence of a normal ventricular CSF.