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Progressive Apraxia of Speech as a Sign of Motor Neuron Disease
Joseph R. Duffy, Richard Peach, Edythe A. Strand

Motor neuron disease (MND) is very infrequently associated with aphasia or dementia. Although reports of cases with nonfluent aphasia and MND sometimes imply the presence of apraxia of speech (AOS), their co-occurrence has not been clearly described. This study documents the presence of AOS in seven patients with MND. Dysarthria was present in all seven patients, but the AOS was worse than the dysarthria in four and about equally severe as the dysarthria in two. Dysarthria type was spastic-only in three, mixed spastic-flaccid in three, and probably spastic and/or flaccid in one patient. Nonverbal oral apraxia was present in four and equivocally present in two patients. Aphasia or dementia was present in three patients. These findings establish that AOS can occur in MND, usually or always with dysarthria, but with or without aphasia or other cognitive deficits. Thus, a diagnosis of MND does not preclude the presence of AOS and, more important, MND should be a diagnostic consideration when AOS is the first or a prominent sign of degenerative disease. Finally, the management of communication disorders in people with MND who have both AOS and dysarthria is likely to be more complicated than when only dysarthria is present.

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