Progressive apraxia of speech as a sign of motor neuron disease

Purpose: To document and describe in detail the occurrence of apraxia of speech (AOS) in a group of individuals with a diagnosis of motor neuron disease (MND). Method: Seven individuals with MND and AOS were identified from among 80 patients with a variety of neurodegenerative diseases and AOS (J. R. Duffy, 2006). The history, presenting complaints, neurological findings, and speech-language findings were documented for each case. Results: Spastic or mixed spastic-flaccid dysarthria was present in all 7 cases. The AOS was judged as worse than the dysarthria in 4 cases. Nonverbal oral apraxia was eventually present in all cases. Aphasia was present in 2 cases and equivocally present in another 2. Dementia was present in 1 case and equivocally present in 2. Conclusions: AOS can occur in MND, typically also with dysarthria, but not invariably with aphasia or other cognitive deficits. Thus, a diagnosis of MND does not preclude the presence of AOS. More importantly, MND should be a diagnostic consideration when AOS is a prominent sign of degenerative disease.