幼兒大前庭導水管症候群

Large Vestibular Aqueduct Syndrome in Children

隨著高解析度電腦斷層攝影與磁振造影的廣泛使用，大前庭導水管是目前影像診斷學上常見的內耳畸形之一，大多數有出生後或早期的感音神經性聽力損失，部分併有傳音性聽力損失，而只極少數呈現聽力正常。國內尚未有大前庭導水管症候群病例的報告，為瞭解國內病例與國外病例之臨床表現的異同，於是進行此研究。收集自1988年1月至1998年6月止，作者經驗的大前庭導水管症候群病例，總計8名病例（男性5名，女性3名），被發現聽力異常的年齡分布從1歲9個月至5歲9個月不等，平均2.9歲，其後均有配戴助聽器。8例(100%)均呈兩側前庭導水管不正常擴大，其中4耳(25%)併有其他內耳畸形，均是異常擴大的前庭。初診時聽力圖顯示16耳(100%)都有感音神經性聽力損失，9耳(56%)呈下降漸傾型，6耳(38%)呈水平型，1耳谷型。10耳(63%)同時有低頻的傳音性聽力損失。8例(100%)均曾有突發性感音神經性聽力損失，大部分是反覆發生，其中5例(63%)的突發性聽力損失常與上呼吸道感染或劇烈運動有關。4例(50%)有眩暈或不平衡的前庭症狀，8耳曾接受溫差試驗，結果有4耳(50%)呈現反應低下或無反應。在追蹤中有9耳(56%)呈漸進性聽力損失的現象，純音聽力閾值平均上升29dB；6耳(38%)呈穩定性聽力損失。對於大前庭導水管患者，雖然目前並無有效保護或恢復聽力的方法，但早期診斷可以預為限制病童的活動，以減緩聽力的惡化；因此所有先天性感音神經性聽力損失的兒童，尤其有突發性或波動性聽力損失者，都應接受顳骨電腦斷層攝影檢查，以便儘早診斷大前庭導水管或其他內耳畸形。至於兩側聽力若喪失到助聽器沒有幫助的程度，可以考慮植入人工電子耳。

Large vestibular aqueduct is one of the most common inner ear malformations seen by radiologists. Hearing loss is usually identified soon after birth or in early childhood. Large vestibular aqueduct syndrome is not common in this country, and is seldom reported. We herein report our experience with eight patients (5 boys, 3 girls) with large vestibular aqueduct syndrome. The mean age at presentation of hearing loss was 2.9 years. Computed tomogram showed bilateral large vestibular aqueducts in all children. Sensorineural hearing loss was the predominant feature in all ears. The conductive component of hearing loss was noted in ten ears (63%). The initial audiogram showed a downsloping pattern in nine ears (56%) and a flat pattern in six ears (38%). Sudden sensorineural hearing loss was another characteristic feature, and this occurred in all eight patients. Stable hearing was noted in six ears (38%), while progressive hearing loss was noted in nine ears (56%). In the latter group, the mean pure-tone threshold average (PTA) at presentation was 61dB and the mean final PTA was 90dB. Four children (50%) complained of vestibular symptoms. We suggest that all hearing impaired children with sudden or fluctuating hearing loss should undergo a detailed evaluation, including high resolution computed tomography, to screen for this congenital malformation of the inner ear.