A study of computed tomography of head before lumbar puncture in patients with suspected meningitis

Background: Clinicians routinely order a CT scan of the head before lumbar puncture in patients with suspected meningitis on the premise of risk of uncal or cerebellar herniation likely to be associated with the procedure. Aim: To identify clinical characteristics in patients with suspected meningitis which are likely to be associated with abnormal findings on CT scan of head. Results: We prospectively studied 108 patients (60 males, 48 females) who underwent CT of the head and lumbar puncture after recording base-line clinical features. 81% patients were diagnosed to have meningitis while 19 had pyogenic meningitis; 8 were excluded due to lack of establishment of a definite diagnosis of meningitis. Only 26.8% patients had abnormal CT findings with hydrocephalous (56.8%), cerebral infarct (27.5%), cerebral oedema (24.1%), meningeal enhancement (17.2%), granulomatous lesion (17.2%), basal exudates (13.8%), and subdural effusion (3.4%) being present either in combination or individually. Base-line clinical features that were significantly associated with abnormal CT findings were age > 60 years, abnormal level of consciousness (Glasgow coma scale < 8), facial nerve and/or gaze palsy, focal neurological deficits other than cranial nerve palsy and seizures at presentation. Conclusion: In subjects with suspected meningitis, clinical assessment can be reliably used to identify those patients who are unlikely to have abnormal findings on CT scan of head and thus are at low risk for herniation following lumbar puncture.