Content area
Full Text
Encephalitides are known to cause severe cognitive decline in some patients. Among the acute encephalitides, Herpes simplex virus (HSV) has been the most commonly reported single aetiology leading to dementia. 1-3 Untreated herpes simplex virus encephalitis (HSVE) is fatal in up to 70%, and results in severe deficits in 40%-60% of the survivors. 4-7 Based on data published in the 1960s and 70s, the mortality in any encephalitis was 10%-50%, and 15%-28% of the survivors had neurological disability. 4 8 9 In the 1980s antiviral medication, improvements in neuroimaging, and probably also other developments in the neurointensive care seem to have improved the prognosis. Today the mortality in patients with HSVE treated with acyclovir is 19%-28%, but 18%-42% of survivors are still reported of having severe deficits in follow up. 10 11 Although the sequelae are mostly behavioural and cognitive, neuropsychological methods have not been systematically utilised. Cognitive deficits are often not detected in routine medical assessments. Even in cases with normal mini mental status examination, impairment has been found when a thorough neuropsychological assessment has been used. 12
The damage caused by the herpes simplex virus to the CNS has been found to progress months after the acute stage in some cases untreated with antiviral medication. 13 14 Also, relapses after a seemingly favourable recovery after antiviral treatment have been reported. 15-17 Although this idea is not widely accepted, 18-20 the presumably progressive nature of HSVE has generated the idea of HSV having a role in Alzheimer's disease. 21 22
To the best of our knowledge, no systematic follow up studies assessing the cognitive performance of a group of patients after acute encephalitides exist in the English literature. Previously we found that cognitive impairment initially occurs in 88% of the HSVE and in 56% of the non-HSV encephalitic patients. 23 We now aimed to study (1) does progressive deterioration really occur after acute encephalitis, or (2) do the cognitive deficits found in the acute stage later improve, and (3) how often acute encephalitides cause dementia?
Materials and methods
PATIENTS
Forty five consecutive patients with acute encephalitis were prospectively studied between 1 January 1990 and 31 December 1994. The mean (SD) age of the patients was 40.8 (16.3) years (range 19 to 73), and the...