雙側耳失聰患者耳萵植入手術前以磁振掃描影像評估

Abstract

由於植入耳耳型態上的畸型，使重度聽障甚或 耳聾的病童其植入耳蝸電子耳植入手術後有相當 的可能可引起腦脊髓液外漏及顏面神經障礙等可 能，手術中誤傷到顏面神經的機會也增加；另外， 不正常發育的顳骨中手術有意或無意形成腦脊髓 液漏管或術後耳源性腦膜炎的機會也較大，而某些 影像檢查的異常發現甚至可能改變手術的位置及 方式；因此影像檢查便成為耳蝸電子耳手術術前評 估很重要的部份！ 此研究針對三十例十六歲以下雙側失聰兒童 與十例聽力正常兒童進行磁振掃描影像檢查，採用 1.5T 磁場之磁振掃描儀 Siemens Magnetom Plus (Erlangen, Germany)，磁振掃描檢查施以橫向切面 之二維快速自旋回波(turbo spin echo TSE) 、 constructive interference in steady state (CISS) 序列 檢查，同時也將重組CISS 影像最大訊號強度的投 影像；並以螺旋電腦斷層掃描儀(PQ6000, Picker, Ohio)進行高解析度顳骨電腦斷層影像，各影像由兩 位放射線科醫師判讀，其判讀重點包括：耳蝸的圈 數、耳蝸內淋巴液的訊號是否異常降低、耳蝸是否 變形、前庭與半規管的形態是否異常、是否有明顯 之導水管瘺管、內聽道是否狹窄、測量內聽道內第 八對腦神經的直徑、顏面神經的走向是否異常。挑 選出那一邊最適合植入電子耳，並將影像所見與手 術所見相互比較，重點著重於：耳蝸是否異常鈣化 或纖維化、耳蝸是否變形、以及顏面神經的走向是 否異常。術後追蹤記錄病童能否聽到聲音而有反 應。對於影像顯示有內耳異常發育的患者，則依 Jackler’s classification [a]加以分類。 完成十三例雙側嚴重失聰病童之磁振掃描與 二十五例高解析度電腦斷層影像掃描。並完成十例 聽力正常兒童之磁振掃描影像檢查。判讀並比較耳 蝸的圈數、耳蝸內淋巴液的訊號是否異常降低、耳 蝸是否變形、前庭與半規管的形態是否異常、是否 有明顯之導水管瘺管、內聽道是否狹窄、顏面神經 的走向是否異常等。以求能比較各影像的優劣點以 尋求對於嚴重雙側失聰兒童耳蝸植入術前影像檢 查較為經濟合理的檢查方法。並應用高解析度影像 減少誤植入不適合之耳側而導致的失敗。

Cochlear implant in profoundly deaf children was not commonly performed due to the complex process involving surgery, imaging work-up, auditory functional evaluation and rehabilitation. Not much information about the results of cochlear implantation in children was available. Since there is no widely acceptable classification of malformation of the cochlea based on embryology and imaging findings, the results of pediatric cochlear implantation from various centers are not usually comparable. In addition, cochlear malformation is frequently associated with aberrant course or bifurcation of the facial nerve. The anatomic landmarks are usually absent in patients with cochlear malformation. One of the major concern during operation is to prevent incidental injury to the facial nerve. Thorough knowledge of the morphologic changes of cochlear malformation can not be overemphasized for the surgical approach of cochlear implantation. Due to recent advances of magnetic resonance imaging include three-dimensional Turbo-spin echo (3DTSE) and constructive interference in the steady state (CISS), imaging with thin section and high spatial resolution is possible. The goal of the study was to apply CISS and 3DTSE to demonstrate the morphologic changes of the cochlear malformation, associated semicircular canals and the diameter of facial as well as eighth nerves. Thirty children suffering from bilaterally profound deafness and younger than 16 years old will be included in the study. Another ten children with normal hearing acuity will also be included as control group. By using 1.5 T Magnetom Plus scanner (Siemens, Erlangen, Germany), these children will undergo 2D TSE, CISS pulse sequences. MIP images deriving from CISS images will also be obtained. In addition, these children will receive high-resolution temporal CT examinations on a spiral CT PQ 6000 scanner (Picker, Ohio). The four sets of images will be read by two radiologist to determine: the number of turns of cochlea, the signal intensity of endolymph within the cochlea, deformity of the cochlea, anomalies of the vestibule and semicircular canals, the vestibular aqueduct fistula, narrowing of the internal auditory canal, the diameter of the 8th nerve within the internal auditory canal, and the course of the facial nerve near the inner ear and middle ear. We will correlate these findings with what will be found during operation. Much attention will paid to the presence of calcification or fibrosis within the implanted cochlea, deformity of the cochlea and aberrant course of the facial nerve. Those congenital anomalies of the inner ear will be classified according to the Jackler’s classification. Whether the patient can hear will be recorded during postoperative follow-up. We intended to compare four kinds of images(2DFSE, CISS, CISS MIP and HRCT) find out the most conomic way to evaluate those bilaterally deaf children. With use of high-resolution images, we also want to cut down the failure rate resulting from implantation in the unsuitable side of ear. We believe that the risk of facial palsy after cochlear implantation will be less if high-resolution images of the inner ear are meticulously read.