"Thalamic" dementia in herpes encephalitis: clinico-pathological report.

Herpes zoster (HZ) primary affections of the CNS are rare and, in most of the reported patients, are representing variously extended forms of ascending myelitis. Our examination concerns a man who at the age of 37 developed apathy after a feverish episode with iridocyclitis. Six months later an ophthalmic HZ was diagnosed and thenceforth the patient showed a dementia with Korsakow's syndrome, apathy and a right hemipalsy, and diplopia appeared; the later symptoms remitted after steroid therapy. Post-mortem examination revealed a slowly progressive encephalitis with symmetrical impairment of the anterior ventral, medial, and centrum medianum of the thalamus. The HZ origin of the lesions and the relation between their site and the peculiar form of dementia, to be ascribed to the "thalamic" ones, are discussed. A vasculitis process can be hypothesized considering both the symmetrical localisation and the microscopical aspects of the lesions.