Background Pace and rhythm of speech and non-speech vocal utterances have recently been shown to be abnormal in speakers with manifest HD and are characterised by a reduced speech rate and irregularities of syllable repetition. On the other hand, speakers with premanifest HD already feature abnormalities of syllable repetition, however, speech rate has been found to be higher than in healthy controls. Therefore, longitudinal studies in premanifest HD subjects should be helpful to illustrate the evolution of the abnormal patterns over time.
Aim The aim of the study was to survey the development of distinctive parameters of speech and non-speech vocal performance in the time course of premanifest Huntington's disease (HD).
Methods We examined 13 speakers with premanifest HD which were tested and re-tested after 22 months using a speech task consisting of a) reading a German text (for the calculation of net speech rate/NSR and pause ratio/PR%) and b) several subtests for the monitoring of non-speech vocal performance to calculate the maximum syllable repetition capacity/maxSylRep and the precision of syllable in a self-chosen steady pace (the coefficient of variance/COV displayed the steadiness of repetition).
Results Disease specific variables as overall motor impairment and the cognitive score became worse over time. Furthermore, in the speech tasks, there was a tendency to a reduction of NSR and maxSylRep and further decline of the steadiness of syllable repetition. The self-chosen pace of syllable repetition was significantly slower at follow-up (p < 0.0001). Moreover, there was a correlation between the reduction of the MRI based volume of the caudate nucleus and a worsening of syllable repetition over time.
Conclusions Abnormalities of speech rate and rhythm are detectable even in the premanifest stages of HD and show a tendency to further deteriorate in the time course of disease progression. Further long-term follow-up studies are warranted to survey the evolution of these distinctive patterns with time which might be helpful for the monitoring of disease progression and could provide some further insight into the underlying pathophysiology of HD.