Dementia and aphasia in motor neuron disease: an underrecognised association?

Objectives-To determine the prevalence and nature of global cognitive dysfunction and language deficits in an unselected population based cohort of patients with motor neuron disease (MND). Methods-A battery of neuropsychological and language tests was administered to patients presenting consecutively over a 3 year period to a regional neurology service with a new diagnosis of sporadic motor neuron disease. Results-The 18 patients could be divided on the basis of their performance into three groups: Three patients were demented and had impaired language function (group 1); two non-demented patients had an aphasic syndrome characterised by word finding difficulties and anemia (group 2). Major cognitive deficits were therefore found in five of the 18 patients (28%). The remaining 13 performed normally on the test battery apart from decreased verbal fluency (group 3). Conclusions-The prevalence of cognitive impairment in MND in this population based study of an unselected cohort was higher than has been previously reported. Language deficits, especially anemia, may be relatively frequent in the MND population. Aphasia in MND may be masked by dysarthria and missed if not specifically examined.