Comparisons of acoustic function in SCA31 and other forms of ataxias

Objective: To investigate whether acoustic impairment can be one of the characteristic extracerebellar symptoms in sporadic and hereditary ataxias including spinocerebellar ataxia type 31 (SCA31). Methods: We investigated genotypes of dominant ataxia families, and determined a frequency of each form in our cohort of 154 families. Acoustic function in the groups of various forms of ataxia with multiple system atrophy of cerebellar predominance (MSA-C), cortical cerebellar atrophy (CCA), and hereditary ataxias including SCA31 was evaluated by using audiogram and brainstem auditory evoked potentials (BAEPs). Results: Genetic analysis of dominant ataxia families revealed that a frequency of SCA31 in our cohort was fewer than that reported from other areas of Japan, indicating that SCA31 is not widely distributed throughout Japan. Results of audiogram showed no significant difference of hearing levels among ataxic groups, and those of BAEPs did not support inner ear dysfunction in SCA31 in which hearing loss had initially been suggested as one of its characteristic symptoms. Conclusion: This study suggests that acoustic impairment is neither specific to SCA31, MSA-C and CCA nor useful in making a differential diagnosis among them.