COGNITIVE IMPAIRMENT AFTER ACUTE ENCEPHALITIS - COMPARISON OF HERPES-SIMPLEX AND OTHER ETIOLOGIES

Objective-To compare the cognitive defects after acute acyclovir treat ed herpes simplex encephalitis with those after other types of acute e ncephalitis. Methods-Seventy seven consecutive patients between 1985 a nd 1995 and 29 normal controls were studied. Of the 77 patients withou t concomitant neurological conditions, 17 had herpes simplex, one viru s encephalitis (HSVE group), 27 had some other identified aetiology (n on-HSVE group), and in 33 patients the cause was unknown. Acyclovir tr eatment was started less than four days after the first mental symptom s in 12 of 17 patients with HSVE. A thorough neuropsychological assess ment was carried out about one month after the onset. Results-The HSVE group had deficits in verbal memory, verbal-semantic functions, and v isuoperceptual functions more often than the non-HSVE group. The risk for cognitive defects was twofold to fourfold in the patients with HSV E compared with the non-HSVE patients. Two (12%) of the patients with HSVE and 12 (44%) of the non-HSVE patients were cognitively intact. Si x patients with HSVE (46%) and 17 (89%) non-HSVE patients later return ed to work. The lesions on CT or MRI were bilateral only in one patien t with HSVE. The defects in the three patients with adenovirus infecti on were severe and resembled the amnesia after HSVE. Cognitive impairm ent, not previously reported, was found in encephalitis after rotaviru s infection and epidemic nephropathy. Conclusion-The recovery in the H SVE group was better than expected based on the medical literature. On the other hand there were surprisingly severe cognitive defects in en cephalitis after other viruses. With early acyclovir treatment patient s with the least severe HSVE were equivalent to those with non-HSV enc ephalitis with good outcome whereas those with the most severe non-HSV encephalitis were equivalent to those with HSVE with poor outcome.