Dysarthria of motor neuron disease: clinician judgments of severity.

Motor Neuron Disease (MND) is a terminal, demyelinating disease affecting upper- and lower-motor neurons and producing muscular weakness resulting in a characteristic spastic-flaccid dysarthria of speech. The present study investigates the relationship between the temporal-acoustic parameters of the speech of 15 individuals with MND as they relate to the progression of the disease and clinicians' judgments of dysarthria severity. When temporal-acoustic parameters are used to predict the progression of MND, it becomes apparent that victims provide compensatory gestures to mark voicing distinctions. When the same acoustic parameters are used to predict clinician judgments of severity, it is found that clinicians tend to use the same temporal cues that mark actual disease progression. Differences between the two sets of predictions relate to the linguistic systems of both speaker and judge, and the implications of this are discussed.