When to Skip CT Before LP for Meningitis

On the Shoulders of Giants

Skip the scan?
When can the CT head be omitted prior to LP in suspected meningitis?  The usual sequence for suspected bacterial meningitis is:

  1. Blood culture
  2. IV antibiotic
  3. CT head without contrast
  4. LP

Delaying antibiotics is harmful.  If it were possible to omit the CT, the LP could be done sooner after antibiotic administration and make recovery of an organism more likely.  These authors found the following clinical features correlated with an abnormal CT in 301 patients.

  • Age of at least 60 years
  • Immunocompromise
  • History of central nervous system disease
  • History of seizure within one week before presentation
  • Abnormal level of consciousness
  • Inability to answer two consecutive questions correctly or to follow two consecutive commands
  • Gaze palsy
  • Abnormal visual fields
  • Facial palsy
  • Arm drift or leg drift
  • Abnormal language (e.g., aphasia)

96 patients had none of the above, and only 3 had an abnormal CT (NPV 97%); none of the 3 had herniation with LP.

Spoon Feed
Patients with suspected bacterial meningitis who have none of the above clinical features on exam may safely undergo LP without prior CT.  The key action is early IV antibiotics.  When in doubt, just give antibiotics, get the CT, and do the LP as soon as you can afterward.  BestBETs has a great summary of the pertinent literature.


Abstract

N Engl J Med. 2001 Dec 13;345(24):1727-33.

Computed tomography of the head before lumbar puncture in adults with suspected meningitis.

Hasbun R1, Abrahams J, Jekel J, Quagliarello VJ.

Author information:

1Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA.

Comment in

Abstract

BACKGROUND:

In adults with suspected meningitis clinicians routinely order computed tomography (CT) of the head before performing a lumbar puncture.

METHODS:

We prospectively studied 301 adults with suspected meningitis to determine whether clinical characteristics that were present before CT of the head was performed could be used to identify patients who were unlikely to have abnormalities on CT. The Modified National Institutes of Health Stroke Scale was used to identify neurologic abnormalities.

RESULTS:

Of the 301 patients with suspected meningitis, 235 (78 percent) underwent CT of the head before undergoing lumbar puncture. In 56 of the 235 patients (24 percent), the results of CT were abnormal; 11 patients (5 percent) had evidence of a mass effect. The clinical features at base line that were associated with an abnormal finding on CT of the head were an age of at least 60 years, immunocompromise, a history of central nervous system disease, and a history of seizure within one week before presentation, as well as the following neurologic abnormalities: an abnormal level of consciousness, an inability to answer two consecutive questions correctly or to follow two consecutive commands, gaze palsy, abnormal visual fields, facial palsy, arm drift, leg drift, and abnormal language (e.g., aphasia). None of these features were present at base line in 96 of the 235 patients who underwent CT scanning of the head (41 percent). The CT scan was normal in 93 of these 96 patients, yielding a negative predictive value of 97 percent. Of the three misclassified patients, only one had a mild mass effect on CT, and all three subsequently underwent lumbar puncture, with no evidence of brain herniation one week later.

CONCLUSIONS:

In adults with suspected meningitis, clinical features can be used to identify those who are unlikely to have abnormal findings on CT of the head.

PMID: 11742046 [PubMed - indexed for MEDLINE]