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Herpes Simplex Encephalitis
05 November 2004
The most common form of nonepidemic encephalitis in adults Prevalence: 3/1,000,000 95% due HSV1 (oral form) but encephalitis & oral ulcers rarely occur together
80% population seropositive for HSV1 10-60% population seropositive for HSV2
CLINICAL Prodrome: 1-5 days of headache, fever Encephalitis: 65% seizures Confusion, stupor, coma Site specific: inferomedial frontal & temporal lobes Olfactory / gustatory hallucinations Anosmia Temporal lobe seizures Personality change Bizarre / psychotic behavior Aphasia
Atypical presentations in immunocompromised hosts
INVESTIGATIONS CSF: pleocytosis, increased protein Intrathecal antibodies to HSV 60% sensitive (false positives with VZV, MS) Done > 3 days after onset Nested HSV PCR: 95% sensitive 100% specific Culture, antigen testing not useful EEG: 73% compatible with HSV in first week 84% compatible with HSV in second week 9% false positive CT: hypodense lesions temporal lobe 70% after 3 days MRI: picks changes earlier than CT Brain biopsy: gold standard 3% complication rate inc death
TREATMENT 10 mg/kg @ 8hrs for acyclovir acyclovir > vidarabine > placebo mortality: 19% 50% 70% no sequelae: 56% 13% acyclovir 1% risk with encephalopathy (lethargy, obtundation, tremors, confusion, hallucinations, agitation, seizures, coma)
OUTCOME 70% mortality untreated 80% survivors have major sequelae (seizures, memory impairment) Dependent upon: age Stage of presentation Time to initiate therapy |
