Case of a scuba diver with motion sickness

動揺病は乗り物などの動揺環境に曝されることに よって前庭神経系が刺激され,視覚系,自己受容器 系よりの刺激が脳幹で統合され自律神経系を介して 発症し,乗り物酔いとしてよく知られる疾患であ る。その発症機序として,動揺による加速度が内耳 を刺激し,その結果,自律神経機能の異常をきたす とする内耳過剰刺激説(overstimulation hypotheMotion sickness (MS) is a familiar complaint among scuba divers. We examined the longterm prognoses of scuba divers suffering from MS. We report the case of a 42-year-old woman with repetitive MS. For 2 years, we tested her otolith organ function every month. The otolith organ function of each ear was tested separately via ocular counter rolling (OCR) testing, which was performed under a 30° head tilt. The R-L side asymmetry ratio for OCR values (% OCRA) was compared with the divers’ static OCR. In addition, we studied the relationship between the %OCRA and climatic factors, such as sunshine exposure duration, global solar radiation, and the UV index. %OCRA scores differed significantly (p<0.01) between our subject and the volunteer diver without MS. There were sharp fluctuations in the %OCRA of our subject diver with MS. MS was more likely to occur in the summer season, especially when the % OCRA exceeded the cutoff value (45.9). There was a significant correlation between the % OCRA and the UV index. Physiological differences in R-L otolith organ function could be involved in the onset of MS. The amount of UV light exposure and female hormone levels may affect the metabolism of the otolith organ. As MS is caused by multiple factors, otolaryngologists need to consider various causative factors beyond those related to the otolith organ function in scuba divers with MS. 原 著