Suspected Meningitis Treatment

Suspected Meningitis Treatment

Objective: Diagnosis of community acquired bacterial meningitis requires CSF testing. However, many centers routinely perform CT scanning of the head before ordering lumber puncture to identify any occult intracranial abnormalities. Clinical findings associated with a low rate of abnormal results on head CT scanning were evaluated in a prospective study.

Methods: The study included 301 adult patients evaluated in an emergency department for suspected meningitis. In 235 patients, head CT was performed before lumber puncture. Prescan clinical characteristics associated with a low likelihood of CT abnormalities were evaluated. Neurologic abnormalities were assessed using the Modified National Institutes of Health Stroke Scale.

Findings: Twenty four percent of patients had abnormal head CT results, including a mass effect in 5%. Certain baseline clinical findings were associated with abnormal CT results, including age 60 years or over, immunocompromise, CNS disease, and seizure within 1 week before presentation. Neurologic findings associated with abnormal CT findings included altered level of consciousness, inability to answer questions or follow commands, gaze palsy, visual field abnormalities, facial palsy, arm or leg drift, and aphasia.

Of the patients undergoing CT scanning before lumber puncture, 41% had none of these characteristics. Of these 96 patients, all but 3 had a normal CT scan results, for a negative predictive value of 97%. These 3 patients proceeded to lumbar puncture with none showing any sign of cerebral herniation at 1 week's follow up.

Conclusion: Among patients with clinically suspected meningitis, those having none of the baseline findings identified in this study can safely undergo immediate lumber puncture with a low risk of subsequent brain herniation. In the authors' experience, applying these predictors can reduce the rate of prelumbar puncture CT by more than 40%. Patients with the identified characteristics should have blood drawn for culture and receive empiric antibiotic therapy before CT scanning is performed.