Cognition, language and behaviour in motor neurone disease: evidence of frontotemporal dysfunction.

Cognitive symptoms accompanying motor neurone disease (MND) have been recognized and described since the late 19th century. Numerous reports from Europe, North America and Japan suggest existence of a syndrome that can be described as MND/dementia. Typically, psychiatric and cognitive changes, strongly reminiscent of frontotemporal dementia, precede the occurrence of the classical signs and symptoms of MND by several months. In a small number of patients a similar picture can be heralded by a progressive aphasia leading ultimately to mutism. While the syndromes of MND/dementia and MND/aphasia constitute a comparatively small group, subtle but consistent cognitive alterations have also been observed in the majority of nondemented MND patients. Although generally much less pronounced, their pattern, affecting mostly frontal-executive functions, resembles that of MND/dementia. Postmortem examination results, describing pathological changes in the frontal lobes, and functional neuroimaging studies, showing abnormal pattern of frontal activation, add more weight to the hypothesis linking MND to the frontotemporal dementia.