Introduction: Dysarthria is one of the first sign of neurological Wilson's disease and is often characterized by a decreased speech rate. The aim of this study is to determine the abilities of Wilson's disease dysarthric patients to control their speech rate. We examined the impact of dual-tasking on the speech rate of patients as compared to healthy control speakers and in relation with their ability to accelerate speech rate when instructed to do so.
Methods: Twenty-six patients and twenty-six age- and sex-matched healthy controls repeated a sentence during 20 seconds at a comfortable speech rate used as reference. They were then asked to perform the same repetition task but in dual task conditions, in which sentence repetition was done while performing three types of executive grapho-motor tasks. Finally, the ability to control speech rate was tested by asking the speakers to perform the sentence repetition task alone but at a fast rate of speech.
Results: A significantly slower speech rate was observed for all patients as compared to controls. In the dual-task conditions, while the speech rate of healthy speakers accelerated significantly, two behaviors are found for the patients. Forty-two percent of the patients reproduced the control pattern with a significant increased in speech rate, while the other group significantly decreased their speech rate. Comparison of the ability of the two groups to intentionally modulate speech rate, when instructed to accelerate, shows that significantly better acceleration was achieved by speakers in the former group compared with the latter.
Conclusions: This study supports the finding that patients with Wilson's disease exhibit an impaired speech rate and also impaired control of speech rate. Indirect assessment of speech rate modulation with the help of a dual-task paradigm has proven to be useful to distinguish patient behaviors. This paradigm could also be envisioned as a tool for rehabilitation.
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