viral encephalitis
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Etiology
- common
- Herpes simplex virus (HSV)-1 (50-75%)[8]
- Varicella zoster virus
- arboviruses
- encephalitis virus, between June & October[2]
- enteroviruses (< 34 years of age) between May & Nov[2]
- mumps virus
- less common
- rare
Epidemiology
- 48% of encephalitis is viral encephalitis
- Herpes encephalitis most common viral encephalitis
- 2/3 of cases > 40 years of age
- 3000 cases in USA/year 2005; 7 per 100,000[8]
Pathology
- temporal lobe affected with Herpes simplex encephalitis
Clinical manifestations
- herpes encephalitis
- fever
- hemicranial headache
- altered mental status[2]
- focal cranial nerve palsy
- hemiparesis
- ataxia
- focal seizures
- fulminant symptoms evolve over days*
- also see encephalitis virus (includes West Nile virus)
* distinguishing feature from paraneoplastic limbic encephalitis
* also see Herpes simplex encephalitis
Laboratory
- lumbar puncture & cerebrospinal fluid analysis
- CSF cultures generally unrewarding
- PCR/ISH for herpes simplex virus DNA
- 95% sensitivity, 98% specificity[2]
- may be negative early during the course of HSV encephalitis
- repeat testing indicated if initial result is negative & MRI neuroimaging shows temporal lobe inflammation[2]
- CSF serology
- bloody CSF suggests Herpes simplex encephalitis
- mild-moderately elevated CSF protein
- lymphocytic pleocytosis
- CSF glucose is generally normal
- CSF may be normal in 3-5% of patients
- Varicella zoster IgG or Varicella zoster DNA
- IgM antibodies by ELISA for flavivirus (arbovirus)
- brain biopsy (gold standard)
Diagnostic procedures
- EEG:
Radiology
- magnetic resonance imaging (MRI)
- areas of increased signal intensity on T2-weighted spin-echo images
- frontotemporal cortex
- cingulate gyrus
- insular regions
- temporal lobe inflammation (Herpes simplex)
- areas of increased signal intensity on T2-weighted spin-echo images
- CT of head with contrast if MRI not available
- temporal-parietal areas of low absorption
- mass effect
- contrast enhancement
Complications
- increased risk for Alzheimer's disease[9]
Management
- neurosurgery consult
- supportive therapy
- intensive care units support
- monitoring of intracranial pressure
- fluid restriction
- avoid hypotonic fluid
- suppression of fever
- prophylaxis for seizures with standard anticonvulsant therapy
- patients at risk for:
- aspiration pneumonia, stasis ulcers, contractures, DVT, infections of lines & catheters
- empiric acyclovir 10 mg/kg IV every 8 hours for 10 days
- do not wait for laboratory confimation[2]
- treatment of choice for Herpes simplex encephalitis[2]
- 14-21 days of treatment for confirmed HSV encephalitis[2]
- effective treatment for arbovirus encephalitis is not available[2]
- discontinue acyclovir if CSF herpes simplex virus DNA is negative[2] unless MRI neuroimaging shows temporal lobe inflammation
- oral acyclovir does not reach therapeutic levels[2]
- neurologic sequellae vary with severity & etiology
More general terms
More specific terms
- AIDS dementia complex; AIDS encephalopathy; HIV-associated dementia (HAD)
- Herpes simplex encephalitis
- Powassan virus
- progressive multifocal leukoencephalopathy (PML)
- Rocio viral encephalitis; Rocio viral infection
- St. Louis encephalitis
- subacute sclerosing panencephalitis (Dawson disease, SSPE)
- viral meningoencephalitis
Additional terms
References
- ↑ Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 2312-14
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 Medical Knowledge Self Assessment Program (MKSAP) 14, 15, 16, 18, 19. American College of Physicians, Philadelphia 2006, 2009, 2012, 2018, 2021.
- ↑ ARUP Consult: Encephalitis, Infectious The Physician's Guide to Laboratory Test Selection & Interpretation https://www.arupconsult.com/content/encephalitis-infectious
- ↑ Tunkel AR, Glaser CA, Bloch KC et al The management of encephalitis: clinical practice guidelines by the Infectious Diseases Society of America. Clin Infect Dis. 2008 Aug 1;47(3):303-27 PMID: https://www.ncbi.nlm.nih.gov/pubmed/18582201 (corresponding National Guideline Clearinghouse entry withdrawn Dec 2013)
- ↑ Singh TD et al. The spectrum of acute encephalitis: Causes, management, and predictors of outcome. Neurology 2015 Jan 27; 84:1 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/25540320 <Internet> http://www.neurology.org/content/early/2014/12/24/WNL.0000000000001190
- ↑ Armangue T, Leypoldt F, Malaga I et al Herpes simplex virus encephalitis is a trigger of brain autoimmunity. Ann Neurol. 2014 Feb;75(2):317-23. PMID: https://www.ncbi.nlm.nih.gov/pubmed/24318406 Free PMC Article
- ↑ 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. PMID: https://www.ncbi.nlm.nih.gov/pubmed/22120595
- ↑ 8.0 8.1 8.2 Rothaus C Viral Encephalitis. NEJM Resident 360. Aug 8, 2018. https://resident360.nejm.org/content_items/viral-encephalitis-2
Rothaus C A Woman with Fever, Headache, and Progressive Encephalopathy NEJM Resident 360. Jan 23, 2019 https://resident360.nejm.org/content_items/a-woman-with-fever-headache-and-progressive-encephalopathy - ↑ 9.0 9.1 George J Viruses Tied to Subsequent Dementia, Other Neurodegenerative Diseases. Viral encephalitis and Alzheimer's disease showed strongest links. MedPage Today January 30, 2023 https://www.medpagetoday.com/neurology/generalneurology/102872
Levine KS, Leonard HL, Blauwendraat C et al Virus exposure and neurodegenerative disease risk across national biobanks. Neuron. 2023. Jan 19 PMID: https://www.ncbi.nlm.nih.gov/pubmed/36669485Free article https://www.cell.com/neuron/fulltext/S0896-6273(22)01147-3 - ↑ National Institute of Neurological Disorders and Stroke (NINDS) NINDS Encephalitis and Meningitis Information Page https://www.ninds.nih.gov/Disorders/All-Disorders/Meningitis-and-Encephalitis-Information-Page