Vestibular Performance During High-Acceleration Stimuli Correlates with Clinical Decline in SCA6
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In spinocerebellar ataxia type 6 (SCA6), the vestibular dysfunction and its correlation with other clinical parameters require further exploration. We determined vestibular responses over a broad range of stimulus acceleration in 11 patients with SCA6 (six men, age range=33–72 years, mean age±SD=59±12 years) using bithermal caloric irrigations, rotary chair, and head impulse tests. Correlations were also pursued among disability scores, as measured using the International Cooperative Ataxia Rating Scale, disease duration, age at onset, cytosine-adenine-guanine (CAG) repeat length, and the gain of the vestibulo-ocular reflex (VOR). In response to relatively low-acceleration, low-frequency rotational and bithermal caloric stimuli, the VOR gains were normal or increased regardless of the severity of disease. On the other hand, with relatively high-acceleration, high-frequency head impulses, there was a relative increase in gain in the mildly affected patients and a decrease in gain in the more severely affected patients and gains were negatively correlated with the severity of disease (Spearman correlation, R=−0.927, p<0.001). Selective decrease of the vestibular responses during high-acceleration, high-frequency stimuli may be ascribed to degeneration of either the flocculus or vestibular nuclei. The performance of the VOR during high-acceleration, high-frequency head impulses may be a quantitative indicator of clinical decline in SCA6.
KeywordsSpinocerebellar ataxia Vertigo Cerebellum Vestibulo-ocular reflex Head impulse test
This study was supported by a grant of Korea Medical Device Industrial Cooperative Association.
Conflict of Interest
Drs. Huh, Park, J.M. Kim, and J. W. Cho, and Ms. H.J. Kim report no disclosure.
Dr. J.S. Kim serves as an Associate Editor of Frontiers in Neuro-otology and on the Editorial Boards of the Journal of Korean Society of Clinical Neurophysiology, Research in Vestibular Science, Journal of Clinical Neurology, Frontiers in Neuro-ophthalmology, Journal of Neuro-ophthalmology, and Journal of Vestibular Research and received research support from SK Chemicals, Co. Ltd.
Dr. Jeon has received funding for travel from Novartis Korea and GlaxoSmithKline Korea and has received research support as PI from Norvartis, Boehringer Ingelheim, Ipsen, the Korea Health 21 R&D project, Ministry of Health & Welfare, Republic of Korea (A101273), the National Research Foundation of Korea(NRF), Ministry of Education, Science and Technology (2010-0021653), Advanced Biometric Research Center (ABRC), Korean Science and Engineering Foundation (KOSEF), Seoul National University Hospital, the Mr. Chung Suk-Gyoo and Sinyang Cultural Foundation, and the Song Foundation.
Dr. Zee receives research support from the National Institutes of Health and is an Associate Editor of Frontiers in Neuro-otology and a member of the Editorial Board of the Cerebellum. He received speaker’s honoraria from Abbott and Micromed and from Sun Pharmaceuticals and from the American Academy of Neurology.
Drs. J.S. Kim and Zee conducted the design and conceptualization of the study, interpretation of the data, and drafting and revising the manuscript. Dr. Huh conducted the design and conceptualization of the study, wrote the manuscript, and analyzed and interpreted the data. Drs. Park, Jeon, J.M. Kim, and Cho contributed to the study concept and design and interpreted the data. Ms. H.J. Kim analyzed and interpreted the data.
Video Head impulse test in patient 1. Bedside head impulse tests were positive in both horizontal directions with corrective saccades. Bedside head impulse tests were performed manually with a rapid rotation of the head in the planes of the horizontal canals. Head impulse test was considered abnormal if a corrective saccade had to be generated to maintain fixation on the target because the slow phase was of the wrong amplitude (MPG 975 kb)
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