Who should have a head CT prior to lumbar puncture (LP) for suspected meningitis?
Patients with immunocompromise, papilledema, preexisting CNS disease, new onset seizures, altered level of consciousness, and focal neurological findings should have a head CT prior to LP.1 While herniation is rare after LP for purulent meningitis, patients with increased intracranial pressure at risk for herniation often have normal head CT scans. Therefore, herniation may be an uncommon but unpredictable complication of LP in this setting. The cause-and-effect relationship of herniation and LP has also been questioned. 2. Are there any cerebrospinal fluid (CSF) findings that exclude bacterial meningitis? A number of CSF findings make bacterial meningitis quite likely, including total leukocyte counts of more than 2,000/mm3, a positive gram stain, or very low CSF glucose. It is difficult, if not impossible, however, to exclude bacterial meningitis in patients with any degree of CSF pleocytosis. For example, 10% of patients with bacterial meningitis have less than 100 WBCs/mm3 in CSF,
