AMNESIA IN ACUTE HERPETIC AND NONHERPETIC ENCEPHALITIS

Objectives: To evaluate how often global amnesia syndrome is encounter ed as a sequel of herpes simplex virus type 1 encephalitis (HSVE) nd i n other types of acute encephalitides, and lo evaluate whether there a re qualitative differences in amnesia caused by different encephalitid es. Subjects: Forty-five consecutive patients with encephalitis (mean age, 40.8 years) studied prospectively within a 5-year period, 8 of wh om had HSVE. There were 24 normal controls. Measures: Neuropsychologic al assessment and memory evaluation after the acute stage of encephali tis, as well as at follow-up after 27.7+/-18.6 months. Results: Three patients (6%), including 1 with HSVE, had persistent anterograde and r etrograde memory defects, typical features of global amnesia. Twelve p atients had anterograde amnesia in the first assessment. No statistica lly significant differences in the memory measures were found between the HSVE (n=4) and the non-HSVE (n=8) groups. Some patients had predom inantly semantic difficulty, some had a ''frontal-type'' memory disord er, and in some patients rapid forgetting was the prominent feature. C onclusions: The frequency of amnesia can reliably be evaluated only in consecutive series of patients. Previous literature, mainly case repo rts, may give the impression that global amnesia is a common consequen ce of encephalitis. Our findings do not support that view. Furthermore , there are clear differences in the quality of the memory impairment between cases of acute encephalitides. Our findings suggest that amnes ia as a consequence of encephalitis, even HSVE, should not be consider ed a uniform phenomenon.