by Kurt Jellinger
With increasing survival of acute herpes simplex (HSV) encephalitis, (due to recent treatment with vidarabine® - adenine arabinoside and acyclovir), patients surviving acute disease develope persistent neurological and psychiatric dysfunctions, especially Kluver-Bucy syndrome, amnesia and memory dysfunctions, due to extensive necrosis of medial temporal lobes, cingulate gyrus, and thalamus, with cavitation and atrophy of the involved cerebral tissues and rare chronic HSV encephalitis due to persistent inflammatory reaction.
Dementia after HSV encephalitis
Symptoms and course
Frequent persisting symptoms are dysomnia, amnesia, Kluver-Bucy syndrome, impairment of memory which, in some cases, may be mild and evident only on neuropsychological testing. In additon, there may be seizures. In some patients, cognitive dysfunction and other psychiatric symptoms may resemble those in Alzheimer disease and Creutzfeldt-Jakob disease. A small proportion of patients experiences a clinical deterioration or relapse weeks to months or even years, after cessation of antiviral therapy. Sometimes depression, hallucinations, and personality changes occur. The majority of late symptoms show a chronic course with little tendency for repair.
HSV encephalitis may occur in young persons, but also in elderly subjects and in these may pose similar problems as in Alzheimer’s disease patients. The duration of clinical residual symptoms may last many years.
Causes and risk factors
HSV encephalitis is caused mainly by HSV type I virus spreading along olfactory nerve fibres and tracts via trigeminal ganglia into the brain. Reactivation of latent virus in the trigeminal ganglia and spread along centrally projecting nerve roots may also enter the brain. Reactivation of the virus has also previously established latent infection within the brain. Risk factors are concomitant HIV infection and immunological defects.
The incidence of acute HSV encephalitis is estimated as 1 in 250 000 - 500 000 persons per year. All age groups are involved. For dementia after survived HSV encephalitis no epidemiological data are available.
Detection of HSV DNA in CSF using PCR; CCT and MRI can early demonstrate. Demonstration of HSV antibodies in CSF and serum are no useful for early diagnosis, but can confirm HSV infection in chronic or residual cases. CCT and MRI show severe destruction and atrophy of medial temporal lobes, hippocampus, cingulate gyrus (limbic structures) and thalamus; SPECT and PET scans show increased temporo-mesial flow. Brain biopsy (mainly stereotactic) may be used for histological and immunohistochemical diagnosis.
Care and treatment
In the acute phase, antiviral treatment with vidarbin and acyclovir, beginning as soon as possible. In the late or residual state only conservative and rehabilitation treatment possible. High dose immunoglobulin treatment can be tried.
Ongoing research/Clinical trials
HSV I vaccination to reduce risk of HSV-I encephalitis
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Last Updated: Friday 09 October 2009