單側高頻性感覺神經性聽障與威利氏環變異巧合發生

Unilateral High-tone Sensori-neural Hearing Loss Coincident with Variant of Circle of Willis

若有兩側不對稱的聽閾損失時，需考慮耳蝸後聽神經的病變，為了能夠早期發現較小的聽神經瘤，可安排磁振造影。一14歲男性，曾經連續1年內，每天使用兩耳開放式耳機聽隨身聽至少4小時，因為左側高頻性耳鳴1年求診於本院，純音聽力檢查呈現左側4,000與8,000 Hz處之聽力閾值分別為60與65 dBHL，鑒於僅有左側高頻處之聽閾損失，可能有耳蝸後聽神經的病變，遂安排影像學的檢查。血管磁振造影意外發現兩側後交通動脈發育不全，最後，診斷為左側高頻性感覺神經性聽障及後方威利氏環變異。目前尚無文獻證實威利氏環變異是否會影響聽覺功能，本個案或許僅是意外發現，特提出報告，期待未來能有更多的研究與討論。

A retro-cochlear lesion is a possible cause of an asymmetric hearing loss. In order to quickly diagnose a small acoustic neuroma, magnetic resonance image is recommended. A 14-year-old male had listened to a portable music player with open earphones for at least four hours every day for a year. He presented with left high-tone tinnitus for a year and then visited our hospital. Pure tone audiometry revealed that the hearing thresholds were respectively 60 and 65 dBHL in 4,000 and 8,000 Hz of his left ear. Because of left high-tone hearing loss, a retro-cochlear lesion was impressed, and then an image study was scheduled. Magnetic resonance angiography showed hypoplasia of bilateral posterior communicating arteries. Finally, left high-tone sensory-neural hearing loss and variant of posterior circle of Willis were diagnosed (posterior COW variant). COW variant had not been proven to directly influence hearing in the literature. It is limited in the literature if COW variant might influence hearing. This might bean exceptional case. We report it herein and hope for more studies in the future.