Abstract
In recent years, a definitive diagnosis of spinocerebellar ataxia type 3, also known as Machado-Joseph disease (SCA3/MJD), has become possible at an early stage with the development of a gene analysis method. We retrospectively investigated the otoneurological findings of 56 patients (male, 23 patients; female, 33 patients) who had been definitively diagnosed as having SCA3/MJD by gene information retrieval at Tokyo Metropolitan Neurological Hospital. In SCA3/MJD patients, the incidence of abnormal oto-neurological findings, e.g., upgaze palsy, gaze nystagmus, impaired optokinetic nystagmus (OKN), smooth pursuit, and saccade, reduced bilateral vestibulo-ocular reflex (VOR), and impaired visual suppression of VOR, was high. 12 of 56 patients had horizontal gaze palsy, so that those 12 cases were excluded from the later investigation. The reduced bilateral VOR performed by caloric response with cold and/or iced water was observed in 31 of 56 ears within six years of the disease; however, it was observed in all 32 ears of patients who had developed SCA3/MJD more than six years previously. Therefore, reduced bilateral VOR is considered to be a very useful biomarker of SCA3/MJD in clinical diagnosis, especially at six years or more since the onset of the disease. Moreover, the otoneurological findings in the markedly reduced VOR group (six patients) and normal VOR group (six patients) within six years after onset of the disease was investigated. In the markedly reduced VOR group, the incidence of upgaze palsy was higher, the impaired visual suppression of VOR was more advanced, and the mean maximum slow phase velocity of OKN was lower in comparison with the normal VOR group. It could indicate that the brainstem dysfunctions were more severe in the markedly reduced VOR group than in the normal VOR group. This may account for the fact that the bilateral VOR dysfunction in patients with SCA3/MJD may be due to a disorder in the central vestibular system originating from the VOR pathways.
