Computed tomography of the head before lumbar puncture in adults with suspected meningitis.

Background: In adults with suspected meningitis clinicians routinely order computed tomography (CT) of the head before performing a lumbar puncture. Methods: We prospectively studied 301 adults with suspected meningitis to d etermine whether clinical characteristics that were present before CT of th e head was performed could be used to identify patients who were unlikely t o have abnormalities on CT. The Modified National Institutes of Health Stro ke Scale was used to identify neurologic abnormalities. Results: Of the 301 patients with suspected meningitis, 235 (78 percent) un derwent CT of the head before undergoing lumbar puncture. In 56 of the 235 patients (24 percent), the results of CT were abnormal; 11 patients (5 perc ent) had evidence of a mass effect. The clinical features at base line that were associated with an abnormal finding on CT of the head were an age of at least 60 years, immunocompromise, a history of central nervous system di sease, and a history of seizure within one week before presentation, as wel l as the following neurologic abnormalities: an abnormal level of conscious ness, an inability to answer two consecutive questions correctly or to foll ow two consecutive commands, gaze palsy, abnormal visual fields, facial pal sy, arm drift, leg drift, and abnormal language (e.g., aphasia). None of th ese features were present at base line in 96 of the 235 patients who underw ent CT scanning of the head (41 percent). The CT scan was normal in 93 of t hese 96 patients, yielding a negative predictive value of 97 percent. Of th e three misclassified patients, only one had a mild mass effect on CT, and all three subsequently underwent lumbar puncture, with no evidence of brain herniation one week later. Conclusions: In adults with suspected meningitis, clinical features can be used to identify those who are unlikely to have abnormal findings on CT of the head. (N Engl J Med 2001;345:1727-33.) Copyright (C) 2001 Massachusetts Medical Society.