Computed Tomography of the Head Before Lumbar Puncture in Adults with Suspected Meningitis
Hasbun R, Abrahams J, Jekel J, Quagliarello V. “Computed Tomography of the Head Before Lumbar Puncture in Adults with Suspected Meningitis.” NEJM 345 (2001):1727-1733
This study was done to determine if CT of the head is necessary prior to lumbar puncture, as has become common practice in the ED, with the intent to minimize unnecessary imaging and patient radiation exposure.
This was a single center prospective cohort study in which 301 patients with a median age of 40 years and clinically suspected meningitis were enrolled to determine if baseline characteristics/clinical features are predictive of brain abnormality such that lumbar puncture is contraindicated. The following are the demographic and clinical features studied: race (52% white), coexisting conditions (27% overall, 8% CNS disease, 25% immunocompromised), symptoms at presentation (79% headache, 67% fever, 50% photophobia, 46% neck stiffness, 7% seizure one week prior to presentation), signs and laboratory data, GCS (91% 14 or 15), and neurologic findings as assessed using the Modified NIH Stroke Scale (17% focal abnormality).
The baseline clinical features found to be associated with abnormality on CT of the head were age at least 60 years (p<0.001), immunocompromised state (p=0.01), history of CNS disease (p<0.001), seizure within one week of presentation, abnormal level of consciousness (p<0.001), inability to answer two consecutive questions correctly (p<0.001), inability to follow two consecutive commands correctly (p<0.001), gaze palsy (p=0.003), abnormal visual fields (p<0.001), facial palsy (p<0.001), arm drift (p<0.001), leg drift (p<0.001), and abnormal language such as aphasia/dysarthria/extinction (p<0.001). Of the individuals who underwent CT of the head, 96 did not have any of the aforementioned baseline characteristics. However, 3 of those 96 patients did have abnormal findings on CT. Of those 3, only 1 had mass effect present on CT, and all three underwent lumbar puncture without brain herniation.
Mean time from ED admission to lumbar puncture was 5.3 hours for those who had a CT of the head and 3.0 hours for did not undergo CT, p<0.001
Mean time from ED admission to initiation of empiric antibiotic treatment was 3.8 hours for those who underwent CT before LP and 2.9 for those who did not, p=0.09.
Absence of the following baseline characteristics has a 97% negative predictive value of finding abnormalities on CT of the head in patients with suspected meningitis: 60 years of age or greater, immunocompromised, history of CNS disease, seizures within one week of presentation, abnormal level of consciousness, inability to answer two consecutive questions correctly, inability to follow two consecutive commands, gaze palsy, abnormal visual fields, facial palsy, arm drift, leg drift, and abnormal language.
This study’s applicability is limited by its relatively small sample size and the fact that it occurred at a single clinical site. Its utility lies in the potential to reduce the number of CT scans ordered for patients with suspected meningitis. However, given the potential morbidity of an LP in a patient with an undetected brain lesion causing mass effect, the practice of ordering a CT of the head beforehand is likely to continue.