Reviewed by Dr. Adrian Peña
Glimaker M, et al. Clin Infect Dis. 2017 Sep 9 [Epub]

This was a prospective cohort study to evaluate the effect of adherence to different guidelines on the timing of diagnostic lumbar puncture (LP) in acute bacterial meningitis (ABM). The study followed all adults diagnosed with ABM and registered in the national Swedish quality register between 2008 and 2015 (n=815). The primary endpoint of the study was in-hospital mortality; secondary endpoint was a “favorable outcome,” defined as absence of neurologic sequelae at 2-6 months follow-up.

Overall in-hospital mortality in all patients diagnosed with ABM was 8% (68/815), with 50% of patients achieving a favorable outcome at follow-up. In-hospital mortality was 4% (14/323) in patients receiving LP without prior CT imaging of the head, vs 10% (37/378) if CT was done before LP (p<0.001). Favorable outcomes were noted in 62% of those who underwent prompt LP vs 43% of those who had CT before LP (p<0.001). Finally, 41% of patients who underwent an LP-first approach received timely, appropriate antibiotics and corticosteroids within 2 hours of presentation, as compared to only 30% of those who underwent CT brain prior to an LP (p=0.005). The above effects remained significant in multivariate analyses adjusting for various demographic and clinical variables.

In patients suspected to have ABM, prompt recognition and treatment are paramount. There exists a theoretical risk of LP leading to brain herniation, although evidence of this in the literature is limited.1 Current guidelines have differing criteria for obtaining neuroimaging prior to diagnostic LP: the Infectious Diseases Society of America (IDSA) guidelines recommend imaging for GCS score <15,2 the European Society for Clinical Microbiology and Infectious Diseases (ESCMID) recommends it for GCS <10,3 and the Swedish national guidelines set the threshold for imaging at GCS <6.4 Further, unlike the US and European society recommendations, Swedish guidelines do not specifically recommend imaging in patients who are immunocompromised, have new-onset seizures, or a history of central nervous system disease, but rather suggest that performing an LP without prior imaging should be safe unless there is clinical evidence of mass effect on physical examination (i.e papilledema, focal neurologic deficits).4

This study evaluated the effects of adherence to different guidelines on outcomes in ABM. In this cohort, adherence to Swedish guidelines was associated with improved outcomes over adherence to ESCMID or IDSA guidelines, a finding the investigators suggested was due to delay of diagnostic LP and antibiotic therapy when neuroimaging was first obtained. While this study is provocative and reminds the practitioner that brain imaging prior to LP is probably overused, its non-randomized nature and the fact that it only includes patients with confirmed ABM introduces potential confounding and bias. Despite attempts to control for severity of illness, patients who received CT scan prior to LP may have had other risk factors not accounted for in multivariate analysis that placed them at higher risk for negative outcomes compared to those who received prompt LP.

Ultimately, patients who underwent an LP first as opposed to CT imaging prior to LP were more likely to receive timely and appropriate antibiotics and steroids, which is likely related to the improved outcomes seen in this group. While awaiting further evidence, clinicians and health systems should focus on reliable systems to rapidly deliver appropriate therapy for patients with suspected ABM while minimizing delays in LP due to imaging or other factors.

1. Brouwer MC, Thwaites GE, Tunkel AR, van de Beek D. Dilemmas in the diagnosis of acute community-acquired bacterial meningitis. Lancet (2012); 380(9854):1684-92.
2. Tunkel AR, Hartman BJ, Kaplan SL, et al. Practice guidelines for the management of bacterial meningitis. Clin Infect Dis (2004); 39(9):1267-84
3. Van de Beek D, Cabellos C, Dzupova O, et al. ESCMID guideline: diagnosis and treatment of acute bacterial meningitis. Clinical Microbiology and Infection (2016); 22 Suppl 3:S37-62.
4. Glimåker M, Johansson B, Bell M, et al. Early lumbar puncture in adult bacterial meningitis – rationale for revised guidelines. Scand J Infect Dis (2013); 45:657-63.