Motor neurone disease, dementia and aphasia: coincidence, co-occurrence orcontinuum?

Cognitive,and particularly aphasic, symptoms associated with motor neurone disease (MND) are still frequently described as rare and "recently discover ed". This review demonstrates that the association between MND and dementia was described and recognised as an entity as early as 1929, and its close relationship to Pick's disease was postulated in 1932. Changes in language production and comprehension were also observed by early authors, although they were rarely described as aphasia. The striking similarity to the conte mporary descriptions is, however, sometimes obscured by diverging terminolo gy. The syndromes of MND/dementia and MND/aphasia are well established but represent a comparatively small subgroup of MND. In addition, subtle cognit ive alterations have also been reported in non-demented MND patients; most studies have found evidence of frontal-executive dysfunction, similar in pa ttern, but much milder than in patients with frank MND/dementia. These find ings are strengthened further by post-mortem studies demonstrating patholog ical changes in the frontal lobes, and functional neuroimaging studies, sho wing reduced frontal activation. The issue of whether memory, visuospatial skills and language are affected in non-demented subjects remains, however, controversial. Further studies are required to establish whether MND/demen tia and MND/aphasia form separate disease entities or can be viewed as extr eme forms of a cognitive deficit characteristic of MND in general.