Thalamic hematomas: neuropsychological aspects. Report of 11 cases and review of literature.

We have recently observed 11 cases of thalamic hematomas. 5 of them (3 left and 2 right) were submitted to a detailed neuropsychological examination. All hematomas were mainly limited to the thalamus and the internal capsula without significant invasion or compression of surrounding structures. The level of consciousness was usually good. 4 of the 8 patients with left-sided hematomas showed dysphasia and the 3 patients submitted to a detailed neuropsychological examination suffered also severe and persistent mnesic disturbances (verbal and non-verbal). On the other hand, the two patients with right thalamic hematomas presented on neuropsychological testing non-verbal mnesic disturbances and features indistinguishable from right parietotemporal cortical lesions. Vital outcome was highly favourable since no patient died. Functional recovery was also rather satisfactory but formal neuropsychological testing of memory, language and right cortical functions showed significant persistent deficits at time of follow-up in most cases examined. Relevant literature is reviewed and possible pathogenetic mechanisms are discussed. Among various hypothesis concerning neuropsychological impairments, dysfunction of a specific alerting system appears the most seducing possibility but does not explain all observed deficits.