Characteristics of diadochokinesis in multiple sclerosis and Parkinson's disease.

Diadochokinesis (DDK) for speakers with dysarthria has been described using a variety of acoustic measures. A clinical protocol for the objective assessment of DDK requires a unified approach, however, to facilitate implementation across clinics and laboratories. A protocol for the acoustic analysis of DDK that incorporates temporal and energy measures has been used to describe DDK characteristics for dysarthria secondary to stroke as well as ataxic dysarthria. The current study sought to validate and extend the protocol to a new set of etiological groups, including dysarthria secondary to multiple sclerosis (MS) and Parkinson's disease (PD). The results suggest that temporal measures are more useful than energy measures for distinguishing among dysarthria secondary to MS, dysarthria secondary to PD, and healthy controls. The results also highlight the value of including both alternating and sequential motion rate tasks in the assessment of DDK and of supplementing quantitative measures with qualitative spectrographic observations.