Oral diadochokinesis in neurological dysarthrias

Rapid syllable repetitions require alternating articulatory movements and, thus, provide a test for oral diadochokinesis. The present study performed an acoustic analysis of rapid syllable repetitions in patients suffering from idiopathic Parkinson's disease (n = 17), Huntington's chorea (n = 14), Friedreich's ataxia (n = 9), or from a purely cerebellar syndrome (n = 13). Four parameters were considered: the mean number of syllables per train, the median syllable duration with its variation coefficient, and articulatory imprecision in terms of the percentage of incomplete closures. Apart from a few subjects with minor motor deficits only, in all patients at least one of the four measures of diadochokinesis exceeded the normal range. Accordingly, discriminant analysis revealed a highly significant difference between controls and patients with respect to the considered parameters. Thus, oral diadochokinesis tasks represent a sensitive measure of orofacial motor impairment. Moreover, multivariate analysis showed that Parkinson's disease and Friedreich's ataxia are characterized by a highly specific profile of diadochokinesis performance.