Voice Alterations in Patients With Spinocerebellar Ataxia Type 7 (SCA7): Clinical-Genetic Correlations

Spinocerebellar ataxia type 7 (SCA7) is an inherited neurodegenerative disease caused by the expansion of a cytosine-adenine-guanine triplet located in the coding region of the ATXN7 gene, which is characterized by cerebellar ataxia, pigmentary macular degeneration, and dysarthria. Although dysarthria is a common feature in various SCA, its clinical characterization has been barely approached.

In this study, we report, to our knowledge for the first time, a detailed voice analysis in a large series of patients with SCA7, using different vocal parameters, including jitter, shimmer, and fundamental frequency. Patients were molecularly diagnosed using fluorescent-based polymerase chain reaction and capillary electrophoresis, and clinically characterized using the Scale for the Assessment and Rating of Ataxia and the Inventory of Non-Ataxia Symptoms.

We found altered jitter, shimmer, and fundamental frequency measurements in patients with SCA7 compared with control subjects (P < 0.05). However, voice impairment was found unrelated with both age at disease onset and size of the cytosine-adenine-guanine triplet tract. Remarkably, jitter and shimmer measurements of patients were found to correlate with their Inventory of Non-Ataxia Symptoms, but not with their Scale for the Assessment and Rating of Ataxia scores, implying that voice impairment is the result of extra-cerebellar manifestations of the disease.

We propose that deficiency of the extra-cerebellar component of SCA7 might lead to sudden changes in laryngeal muscle tone, producing instability in sustained vowel phonation. Clinical characterization of voice will help to discriminate SCA7 from other SCA and to guide vocal therapy treatments.