The association of motor neuron disease and Alzheimer-type dementia

An elderly woman is described who developed senile dementia of the Alzheimer type, followed within eight months by classical and electromyographic features of sporadic motor neuron disease. Although amyotrophic lateral sclerosis is generally believed to affect the voluntary motor system and spare intellectual function, with the exception of certain familial forms and geographic isolates in the Pacific, pathological involvement of the cerebral cortex and posterior columns has often been demonstrated. A small number of cases of concomitant amyotrophic lateral sclerosis have been reported, but an association has not thereby been proven. With the incidence of dementia increasing, it is possible that epidemiologic studies may show an increase in the incidence of motor neuron disease, and thereby suggest an association. A unitary hypothesis for causation of amyotrophic lateral sclerosis, Parkinson's disease, and Alzheimer's disease has been proposed. Closer investigation of patients with motor neuron disease for dementia, and inquiry into the incidence of motor dysfunction in demented patients, may yield evidence in support of such a hypothesis.