船酔いを生じやすいスクーバダイバーの1症例

―耳石器機能の経時的変化―

抄録

　Motion sickness (MS) is a familiar complaint among scuba divers. We examined the long-term 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.