When viewing this topic in a different language, you may notice some differences in the way the content is structured, but it still reflects the latest evidence-based guidance.

Last reviewed: 16 Mar 2025
Last updated: 01 Nov 2024

Summary

Definition

History and exam

Key diagnostic factors

  • headache
  • neck stiffness
  • fever
  • altered mental status
  • confusion
  • photophobia
  • vomiting
  • seizures
  • hypothermia (infants)
  • irritability (infants)
  • lethargy (infants)
  • poor feeding (infants)
  • apnea (infants)
  • focal neurologic deficit
  • abnormal eye movement
  • facial palsy
  • balance problems/hearing impairment
  • bulging fontanel in infants

Other diagnostic factors

  • high-pitched cry (infants)
  • rash
  • papilledema
  • Kernig sign
  • Brudzinski sign

Risk factors

  • age ≤5 or ≥65 years
  • crowding
  • exposure to pathogens
  • nonimmunized infants
  • immunodeficiency
  • cancer
  • asplenia/hyposplenic state
  • cranial anatomic defects
  • cochlear implants
  • contiguous infection
  • smoking

Diagnostic tests

1st tests to order

  • cerebrospinal fluid (CSF) cell count and differential
  • CSF protein
  • CSF glucose
  • CSF Gram stain
  • CSF culture
  • antigen detection in CSF
  • blood culture
  • CBC and differential
  • CRP
  • electrolytes, calcium (Ca), magnesium (Mg), glucose
  • coagulation profile (prothrombin time, INR, activated PTT, fibrinogen, fibrin degradation products)
  • CT head
  • polymerase chain reaction (PCR)

Tests to consider

  • MRI head
  • serum procalcitonin

Treatment algorithm

Contributors

Authors

Rodrigo Hasbun, MD, MPH

Professor of Medicine

UT Health Mc Govern Medical School

Houston

TX

Disclosures

RH has received research support and personal fees from Biomeriaux.

Omaima El Tahir, MD

PhD Candidate

Department of Pediatric infectious Diseases and Immunology, AI&II

Amsterdam UMC, Vrije Universiteit Amsterdam

Amsterdam

The Netherlands

Disclosures

OET declares that she has no competing interests.

Acknowledgements

Dr Rodrigo Hasbun and Omaima El Tahir would like to gratefully acknowledge Dr Marceline Tutu van Furth, previous contributor to this topic.

Disclosures

AMTvF declares that she has no competing interests.

Peer reviewers

Guy Thwaites, MA, MBBS, PhD, MRCP, FRCPath

Wellcome Trust Clinical Research Fellow

Centre for Molecular Microbiology and Infection

Imperial College London

London

UK

Disclosures

GT declares that he has no competing interests.

Wendy Ziai, MD, MPH

Assistant Professor

Neurology, Neurosurgery, and Anesthesiology and Critical Care Medicine

The Johns Hopkins University

Baltimore

MD

Disclosures

WZ declares that she has no competing interests.

Use of this content is subject to our disclaimer