Dysarthria of motor neuron disease: longitudinal measures of segmental durations.

Motor neuron disease encompasses a group of terminal, demyelinating diseases affecting upper- and lower-motor neurons and producing muscular weakness resulting in a flaccid, spastic, or spastic-flaccid dysarthria of speech. The present study presents measurements of the temporal-acoustic characteristics of dysarthria in three subjects with Motor Neuron Disease over a two-year recording period. Changes seen over the course of the disease varied by type of motor neuron disease, though all types demonstrated some degree of neutralization of the prevocalic VOT, target vowel duration, and postvocalic closure duration. These changes are discussed with relation to physical manifestation and progression of the disease.