Editors' note: Motor speech patterns in Huntington disease

Abstract

In the article “Motor speech patterns in Huntington disease,” Drs. Diehl et al. identified 4 distinct presentations of dysarthria in patients with Huntington disease (HD) based on the evaluation of audio recordings of 48 patients by 6 trained raters. The authors postulated that these distinct presentations may be due to divergent pathologic processes. In response, Drs. Rusz and Tykalova argue that the findings of a patient subgroup characterized by an abnormally fast speaking rate was at odds with prior evidence indicating slow speech rate in HD. They note that patients with a bradykinetic phenotype have previously been shown to have a slower speaking rate than those with a choreatic phenotype, challenging the authors' explanation of fast speaking rate as being related to hypokinetic dysarthria. Besides noting the absence of a control group of healthy patients for comparison, they also contend that the remaining 3 HD dysarthric subgroups may simply reflect overall disease progression. Responding to these comments, the authors cite prior work reporting a higher rate of speech in patients with HD and argue that the studies cited by Drs. Rusz and Tykalova relied on acoustic measures that may only weakly correlate with perceptual ratings of dysarthric speech. They note that the trained raters were asked to rate speech relative to what they considered normal, and that their study identified CAG repeats and Unified HD Rating Scale motor scores as differing significantly across speech subgroups. This exchange highlights potential challenges with reconciling acoustic-based and rater-based phenotyping of speech patterns in neurologic disease. In the article “Motor speech patterns in Huntington disease,” Drs. Diehl et al. identified 4 distinct presentations of dysarthria in patients with Huntington disease (HD) based on the evaluation of audio recordings of 48 patients by 6 trained raters. The authors postulated that these distinct presentations may be due to divergent pathologic processes. In response, Drs. Rusz and Tykalova argue that the findings of a patient subgroup characterized by an abnormally fast speaking rate was at odds with prior evidence indicating slow speech rate in HD. They note that patients with a bradykinetic phenotype have previously been shown to have a slower speaking rate than those with a choreatic phenotype, challenging the authors' explanation of fast speaking rate as being related to hypokinetic dysarthria. Besides noting the absence of a control group of healthy patients for comparison, they also contend that the remaining 3 HD dysarthric subgroups may simply reflect overall disease progression. Responding to these comments, the authors cite prior work reporting a higher rate of speech in patients with HD and argue that the studies cited by Drs. Rusz and Tykalova relied on acoustic measures that may only weakly correlate with perceptual ratings of dysarthric speech. They note that the trained raters were asked to rate speech relative to what they considered normal, and that their study identified CAG repeats and Unified HD Rating Scale motor scores as differing significantly across speech subgroups. This exchange highlights potential challenges with reconciling acoustic-based and rater-based phenotyping of speech patterns in neurologic disease.