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CNS Infections in the US: Room for Improvement in Treatment

Amesh A. Adalja, MD, FACP, FACEP, FIDSA, April 21, 2017

Infections of the central nervous system are one of the most challenging aspects of infectious disease medicine, as they often represent true medical emergencies. Prompt diagnosis and effective antimicrobial therapy are crucial to minimizing morbidity and mortality. In most situations, initial therapy is empiric and based largely on epidemiology because definitive diagnostic test results are not immediately available. Therefore, a thorough understanding of the epidemiology of these infections is crucial. A new paper published in Clinical Infectious Diseases provides detailed information on the epidemiology of encephalitis and meningitis in the United States. 


Premier Healthcare Database Used

In this study, Hasbun et al queried the Premier Healthcare Database, the largest US hospital discharge database, for adult patients with discharge or admission diagnosis of meningitis or encephalitis between 2011 and 2014. A total of 26,429 adults were included in the study. Important study population demographic variables included:

  • 53.3% female 
  • median age of 43
  • 4.2% HIV +
  • 91.2% were admitted via the emergency department


Etiologies and Therapies

The most common single etiology identified was enteroviruses, which accounted for 59% of infections; bacterial etiologies collectively comprised 16% of infections. Nearly 22% of etiologies were undetermined, however.

Intravenous antibiotics were given to 85.8% of patients, intravenous antivirals to 53.4%, and intravenous antifungals to 7.8%. Antibiotic therapy was used in the majority of viral infections and almost universally in those with bacterial etiologies. Antiviral therapy was used similarly in those with viral etiologies as well as those with bacterial etiologies (41.6%). Adjunctive steroids, a key component of the management of pneumococcal meningitis, were used in 39% of patients with this diagnosis and were, predictably, associated with improved outcomes.

Mortality rates ranged from 8.9% for arboviral infections to 0.5% for those with enteroviral infections; bacterial meningitis was associated with an 8.2% mortality rate.


Room for Improvement with Better Diagnostics

This study provides much insight into how both meningitis and encephalitis are treated in the United States. The results argue that there is substantial room for improvement in antimicrobial stewardship and guideline-concordant therapy. Using antibacterial therapy for true bacterial etiologies and antiviral therapy for true viral etiologies would minimize inappropriate use of antibiotics and limit downstream complications, including resistance and C. difficile infection. Similarly, ensuring empiric corticosteroids are given to those with possible pneumococcal meningitis would foster better outcomes.

While part of the gap in clinical care may be due to failure to adhere to evidence-based guidelines, it is likely worsened by traditional microbiological paradigms. As routine cultures may take 2 to 3 days to provide results, there is an opportunity to improve management just by accelerating the time to specific diagnosis and diminishing unknown etiologies (which may provide added epidemiological insights). As syndromic diagnostic CNS testing panels are becoming available, it will be essential to incorporate their use into the management of these infections and study the impact they have on outcomes and stewardship.



Hasbun R, Rosenthal N, Balada-Llasat JM, et al. Epidemiology of meningitis and encephalitis in the United States from 2011-2014. Clin Infect Dis April 17, 2017. Accessed April 18, 2017.