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
Other diagnostic factors
- cough
- gastrointestinal infection
- seizures
- biphasic illness
- autonomic and hypothalamic disturbances
- myocarditis/pericarditis
- jaundice
- arthritis
- retinitis
- parkinsonism
Risk factors
- age <1 or >65 years
- immunodeficiency
- vector exposure and/or animal bites
- location
- vaccination
- postinfection
- blood/body fluid exposure
- organ transplantation
- season
- occupation
- hunting/trekking in woods
- swimming or diving in warm freshwater or nasal/sinus irrigation
- spelunking (cave-exploring)
- death in animals
- cancer
Diagnostic tests
1st tests to order
- CBC
- peripheral blood smear
- serum electrolytes
- liver function tests
- blood cultures
- throat swab
- nasopharyngeal aspirate
- chest radiography
- CT brain
- MRI brain
- electroencephalogram (EEG)
- cerebrospinal fluid (CSF) analysis
- CSF culture
- CSF serology
- CSF polymerase chain reaction (PCR)
Tests to consider
- stool enteroviral culture
- sputum culture
- IgG and IgM antibodies (blood or CSF)
- 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
Treatment algorithm
immunocompetent host: suspected viral etiology
immunocompromised host: suspected viral etiology
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
convalescent phase: all etiologies
Contributors
Authors
Sung G Ji, MD, PhD
Behavioral Neurology Fellow
Department of Neurology
University of Washington
Seattle
WA
Disclosures
SGJ declares that he has no competing interests.
Payal B. Patel, MD
Assistant Professor of Neurology
Department of Neurology
University of Washington
Seattle
WA
Disclosures
PBP has received research funding support from the National Institute of Health and Bayer Pharmaceuticals. PBP has received an honorarium as an author from Medlink Neurology and Continuum Neurology.
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
Alejandro Rabinstein, MD
Professor of Neurology
Mayo Clinic
Rochester
MN
Disclosures
AR has participated in advisory board meetings for Astra Zeneca, Chiesi, and Shionogi.
Rodrigo Hasbun, MD, MPH, FIDSA
Professor of Medicine
UT Health McGovern Medical School
Houston
TX
Disclosures
RH has received research support and personal fees from Biomeriaux (Biofare Diagnostics).
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.
References
Key articles
Venkatesan A, Tunkel AR, Bloch KC, et al. Case definitions, diagnostic algorithms, and priorities in encephalitis: consensus statement of the International Encephalitis Consortium. Clin Infect Dis. 2013 Oct;57(8):1114-28.Full text Abstract
Solomon T, Michael BD, Smith PE, et al. Management of suspected viral encephalitis in adults--Association of British Neurologists and British Infection Association National Guidelines. J Infect. 2012 Apr;64(4):347-73.Full text Abstract
Miller JM, Binnicker MJ, Campbell S, et al. Guide to utilization of the microbiology laboratory for diagnosis of infectious diseases: 2024 update by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM). Clin Infect Dis. 2024 Mar 5:ciae104.Full text Abstract
Kneen R, Michael BD, Menson E, et al. Management of suspected viral encephalitis in children - Association of British Neurologists and British Paediatric Allergy, Immunology and Infection Group national guidelines. J Infect. 2012 May;64(5):449-77.Full text Abstract
Reference articles
A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.
Differentials
- Viral meningitis
- Encephalopathy (toxic/metabolic)
- Status epilepticus
More DifferentialsGuidelines
- Guide to utilization of the microbiology laboratory for diagnosis of infectious diseases
- Canadian consensus guidelines for the diagnosis and treatment of autoimmune encephalitis in adults
More GuidelinesPatient information
Meningitis and septicemia
Lumbar puncture
More Patient information
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