When is a CT scan of the head indicated in suspected meningitis?

Updated: Jul 16, 2019
  • Author: Rodrigo Hasbun, MD, MPH; Chief Editor: Michael Stuart Bronze, MD  more...
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A screening computed tomography (CT) scan of the head may be performed before LP to determine the risk of herniation. A prospective study involving 301 adults with suspected meningitis found that the following baseline patient characteristics were associated with an abnormal finding on head CT [22] :

  • Age ≥60 years

  • Immunocompromise (ie, HIV infection/AIDS, immunosuppressive therapy, or transplantation)

  • A history of CNS disease

  • A history of seizure within 1 week before presentation

  • Any abnormality on neurologic examination

These factors have been included in the Infectious Diseases Society of America guidelines to decide who should undergo CT before LP. [23]

Obtaining a CT scan in a patients without any of the IDSA guidelines indications is of no clinical benefit and should be avoided. [24]

The decision to obtain a brain CT scan before LP should not delay the institution of antibiotic therapy; such delay can increase mortality. It should be also noted that herniation can occur in patients with bacterial meningitis who have a normal brain CT scan. The most reliable clinical signs that indicate the risk of herniation include deteriorating level of consciousness, brainstem signs, and a very recent seizure.

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