Encephalitis

Last reviewed: 26 Apr 2022
Last updated: 05 Nov 2021

Summary

Definition

History and exam

Key diagnostic factors

  • fever
  • rash
  • altered mental state
  • focal neurologic deficit
  • meningismus
  • parotitis
  • lymphadenopathy
  • optic neuritis
  • acute flaccid paralysis
  • movement disorder
More key diagnostic factors

Other diagnostic factors

  • cough
  • gastrointestinal infection
  • seizures
  • biphasic illness
  • autonomic and hypothalamic disturbances
  • myocarditis/pericarditis
  • jaundice
  • arthritis
  • retinitis
  • parkinsonism
Other diagnostic factors

Risk factors

  • age <1 or >65 years
  • immunodeficiency
  • vaccination
  • postinfection
  • blood/body fluid exposure
  • organ transplantation
  • animal or insect bites
  • location
  • season
  • occupation
  • hunting/trekking in woods
  • swimming or diving in warm freshwater or nasal/sinus irrigation
  • spelunking (cave-exploring)
  • death in animals
  • cancer
More risk factors

Diagnostic investigations

1st investigations to order

  • CBC
  • peripheral blood smear
  • serum electrolytes
  • liver function tests
  • blood cultures
  • throat swab
  • nasopharyngeal aspirate
  • sputum culture
  • chest radiography
  • CT brain
  • MRI brain
  • electroencephalogram (EEG)
  • cerebrospinal fluid (CSF) analysis
  • CSF culture
  • CSF serology
  • CSF polymerase chain reaction (PCR)
More 1st investigations to order

Investigations to consider

  • urine culture
  • stool enteroviral culture
  • IgG and IgM antibodies (blood)
  • PCR (blood)
  • HIV serology/RNA test
  • CSF biomarkers/prion protein assay
  • paraneoplastic antibodies (blood and CSF)
  • abdominal/pelvic ultrasound
  • whole-body CT
  • whole-body PET scans
  • magnetic resonance spectroscopy
  • next-generation sequencing of CSF
  • brain biopsy
More investigations to consider

Treatment algorithm

INITIAL

immunocompetent host: suspected viral etiology

immunocompromised host: suspected viral etiology

ACUTE

confirmed herpes simplex virus (HSV) encephalitis

confirmed varicella zoster virus (VZV) encephalitis

confirmed cytomegalovirus (CMV) encephalitis

confirmed Epstein-Barr virus (EBV) encephalitis

confirmed herpes B encephalitis

confirmed human herpes 6 encephalitis

confirmed nonherpes virus etiology

nonviral etiology

ONGOING

convalescent phase: all etiologies

Contributors

Authors

Payal B. Patel, MD

Clinical Instructor

Department of Neurology

Yale University

New Haven

Connecticut

CT

Disclosures

PBP declares that she has no competing interests.

Acknowledgements

Dr Payal B. Patel would like to gratefully acknowledge Dr Leo H. Wang, Dr Louise T. Wang, Dr Catalina C. Ionita, Dr Manjunath Markandaya, Dr David Janicke, Dr Robert Schmidt, and Dr Kimiko Domoto-Reilly, previous contributors to this topic.

Disclosures

LHW, LTW, CCI, MM, DJ, RS, and KDR declare that they have no competing interests.

Peer reviewers

Russel Dale, MBChB, MRCPCH, MSc, PhD

Professor of Paediatric Neurology

The University of Sydney

Consultant Neurologist

The Children's Hospital at Westmead

Sydney

Australia

Disclosures

RD declares that he has no competing interests.

Arun Venkatesan, MD, PhD

Associate Professor, Neurology

Director

Johns Hopkins Encephalitis Center

Johns Hopkins Hospital

Baltimore

MD

Disclosures

AV declares that he has no competing interests.

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