第76回日本めまい平衡医学会テーマセッション１「蝸牛vs 前庭：類似点と相違点」
遺伝性難聴から見た蝸牛と前庭
2018 年 77 巻 3 号 p. 180-187
詳細
2018 年 77 巻 3 号 p. 180-187
We summarize the similarities and differences between the cochlea and vestibular endorgans in relation to mutations of genes causing hereditary hearing loss. In regard to the gene expressions associated with hereditary hearing loss in the inner ear, most of the genes expressed in the cochlea are also expressed in the vestibular end-organs. This implies that the genes associated with hereditary hearing loss also function in the vestibular endorgans, and mutations in these genes leading to hearing loss phenotypes may be associated with vestibular dysfunction phenotypes and/or symptoms. We searched the literature for the frequency of vestibular symptoms in patients with mutations in the causative genes for hearing loss. Although 67.3% of the patients with SLC26A4 mutations complained of vestibular symptoms, few patients with other mutations of genes known to cause hereditary hearing loss complained of vestibular symptoms.
SLC26A4 and COCH mutations have been reported to be the most frequently associated with vestibular dysfunction and/or symptoms. Characteristically, in patients with SLC26A4 mutations, vertigo episodes are associated with acute hearing deterioration, and in patients with COCH mutations, progressive vestibular dysfunction is associated with progressive hearing loss. Although 4% of patients with GJB2 mutations complained of vestibular symptoms, saccular dysfunction was more frequent.
It is difficult to explain the absence of vestibular symptoms in most patients with mutations of the causative genes for hearing loss?. Possible explanations for this inconsistency are the presence and functioning of other molecules to compensate for the functional loss of sensory activity in the vestibular end-organs; congenital or slowly progressive vestibular dysfunction could be compensated by visual and somatosensory input. Furthermore, the vestibular sensory system may have a lower sensitivity than the auditory system. Further studies are required to elucidate the effects of mutations linked to deafness on the vestibular functions.
