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Herpes simplex encephalitis

see viral encephalitis Epidemiology: - most common cause of sporadic encephalitis in the U.S. [1] - more common in neonates & adults >= 50 years Pathology: - necrosis of temporal lobe(s) Clinical manifestations: 1) acute in onset in immunocompetent patients - fulminant symptoms evolve over days* 2) fever is generally present 3) altered mental status [1] a) disorder of arousal -> obtundation b) language impairment, aphasia c) personality change d) behavioral disorder e) memory impairment, amnesia f) psychosis 4) encephalopathy 5) seizures, focal seizures, temporal lobe seizures 6) hemicranial headache 7) focal neurologic deficits a) focal cranial nerve palsy b) hemiparesis 9) ataxia may be confused with vertigo * distinguishing feature from paraneoplastic limbic encephalitis Laboratory: - CSF analysis may show lymphocytic pleocytosis - CSF lymphocytes 100-200 cells/uL - CSF protein may be elevated - occasional CSF RBC in non-traumatic taps - Herpes simplex DNA in CSF - may be falsely negative early [1,3] - repeat in 3-7 days if high index of suspicion - do not order Herpes simplex serology or Herpes simplex culture [1] Special laboratory: - EEG may be abnormal - periodic lateralizing epileptiform discharges [1] Radiology: - neuroimaging - brain MRI may show fluid-attenuated inversion recovery (FLAIR) signals in one or both temporal lobes &/or orbito-frontal lobes Differential diagnosis: - paraneoplastic limbic encephalitis evolves over weeks to months Complications: - lethal if not treated [1] - neurological impairment is common among survivors [2] - increased risk of Alzheimer's disease [5] - increased risk acyclovir crystalization & precipitation in renal tubules with high dose acyclovir in patients with hypertension & diabetes mellitus [7] Management: - high-dose intravenous acyclovir for 2-3 weeks - intravenous normal saline to maintain urine output > 75 mL/hour if rise in serum creatinine [7] - oral valacyclovir for 3 months following IV acyclovir of no cognitive benefit [2]

General

limbic encephalitis viral encephalitis Herpes simplex (HSV) or Herpes hominis

References

  1. Medical Knowledge Self Assessment Program (MKSAP) 16, 17. American College of Physicians, Philadelphia 2012, 2015 - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  2. Gnann JW Jr et al. Herpes simplex encephalitis: Lack of clinical benefit of long-term valacyclovir therapy. Clin Infect Dis 2015 Sep 1; 61:683. PMID: 25956891 http://cid.oxfordjournals.org/content/61/5/683 - Tyler KL. Failure of adjunctive valacyclovir to improve outcomes in herpes simplex encephalitis. Clin Infect Dis 2015 Sep 1; 61:692 PMID: 25956893 http://cid.oxfordjournals.org/content/61/5/692
  3. Adler AC, Kadimi S, Apaloo C, Marcu C. Herpes simplex encephalitis with two false-negative cerebrospinal fluid PCR tests and review of negative PCR results in the clinical setting. Case Rep Neurol. 2011 May;3(2):172-8. PMID: 21941494 Free PMC Article
  4. Rothaus C A Returning Traveler with Headache. NEJM Resident 360. Dec 25, 2019 https://resident360.nejm.org/clinical-pearls/a-returning-traveler-with-headache-2
  5. 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: 36669485Free article https://www.cell.com/neuron/fulltext/S0896-6273(22)01147-3
  6. Sabah M, Mulcahy J, Zeman A. Herpes simplex encephalitis. BMJ. 2012 Jun 6;344:e3166. PMID: 22674925 Review.
  7. NEJM Knowledge+ Complex Medical Care