听神经瘤手术的听力保存技术

Technique of hearing preservation during acoustic neuroma surgery

目的探索听神经瘤切除术中保留术前残余听力的可能性，以及评价术中动态听力监测和耳内镜技术对听力保护的效果。方法2003年至2007年7月共收治听神经瘤手术患者138例，对术前有残余听力18例（18耳）施行术中连续听力监测。男6例，女12例；左12耳，右6耳；年龄14～64岁；15例为单发的听神经鞘瘤，3例为神经纤维瘤病Ⅱ型。MRI测得肿瘤最大直径在12～33mm，中位数19．5mm。均采用经乙状窦后入路，10耳辅以耳内镜下手术。18例均行听性脑干反应（ABR）及耳蜗电图术中连续听力监测；术中常规监测面神经功能。术后随访时间为6个月～2．5年，以最后一次听力结果为准。术前及术后听力评价标准采用1995年美国耳鼻咽喉头颈外科学会分级法。结果手术全切16例，大部分切除2例（均为神经纤维瘤病Ⅱ型）。无死亡病例，术后均恢复顺利，无脑脊液漏，无皮下血肿等术后并发症。18例术前均无面神经麻痹，术中面神经均得以保存，解剖结构连续完整。术后7d面神经功能Ⅰ～Ⅱ级占50．0％（9／18）；术后6个月面神经功能Ⅰ～Ⅱ级占88．9％（16／18）。18耳中11耳术后听力得以保存（61．1％），术后听力A级4耳，B级4耳，C级2耳，D级1耳。术前肿瘤〉20mm者共5耳仅2耳保存听力，〈20mm者共13耳术后听力保存9耳（69．2％）。耳内镜辅助下手术10耳，听力保存8耳（80．0％）。术中监测发现，手术过程中当磨钻内耳道后唇、内耳道口附近处牵拉或电凝止血，尤其是夹持内听动脉、处理内耳道处肿瘤及夹持或电凝肿瘤表面最内层蛛网膜血管时，对ABR和耳蜗电图波形影响很大。结论对术前有良好听力的听神经瘤患者应在术中辅以实时动态听力监测，并结合术中耳内镜技术进行听力保护，术后能够获得较好的听力保存效果。听神经瘤表面蛛网膜的保留及其血供状况对保留听力起重要作用，而内听动脉的损伤是术后听觉丧失的最主要原因。

Objective To explore the possibility of hearing protection in acoustic neurinoma （AN） resection and to evaluate the effect of dynamic auditory monitoring and the effect of oto-endoscope for hearing protection. Methods From July 2003 to July 2007, there were a total of 138 cases of AN received surgical treatment. Continuous hearing monitoring was conducted in 18 cases with residual hearing. In these 18 cases, there were 6 males and 12 females, with 12 cases in left side and 6 cases in right. Fifteen cases were solitary AN, 3 cases were diagnosed as neurofibromeatosis Ⅱ. Maximal diameters of the tumor varied between 12 and 33 millimeters with an average of 19. 9 millimeters. All cases were operated on by retrosigmoid approach with routine facial nerve monitoring. Ten cases were assisted by otoendoscope. Eighteen cases were performed accompanying continuous auditory brainstem response （ABR） and electro-cochleogram （EcochG）. The patients were given routine hearing function test 7 to 10 days after operation, and reexamined 6 months to 1 year. The duration of follow-up ranged 6 months to 2. 5 years. Hearing data of the last time was thought as the judging result. Preoperative and postoperative hearing standard refer to （AAO-HNS）classifying. Results In all 18 cases, tumors were rsected completely in 16 cases, but sub-totally removed in 2 cases which were Ⅱ neurofibromeatosis. There was no mortality and no severe complication in this series. All the 18 cases had no facial paralysis before operation, and during operation facial nerves in 18 cases were kept anatomic integrity. According to House-Brackmann grade system, for 18 AN patients 7 days after operation only 50.0% （9/18） were kept at grade Ⅰ to Ⅱ, but 88.9% （16/18） were kept at grade Ⅰ to Ⅱ 6 months after operation. Out of 18 cases, hearing function were preserved in 11 cases （61.1%, 11/18） . After operation, there were 4 cases at hearing grade A, 4 cases at hearing grade B, 2 cases at hearing grade C and 1 cases at hearing grade D. In all 18 cases, there were 5 cases with tumor diameter more than 20 millimeters, in which only 2 cases of them preserved hearing function （2/5）. However, 9 cases preserved their hearing function in the other 13 cases whose tumors diameter less than 20 millimeters （69. 2% ,9/13）. In 10 cases assisted by oto-endoscope, 8 cases obtained hearing protection （ 80. 0%, 8/10） and 2 cases lost hearing. During operative monitoring, when drilling posterior lip of internal auditory canal （ IAC）, dragging and electric coagulating nearby IAC, especially clamping labyrinthine artery, removing tumor in IAC or electric coagulating arachnoid blood vessel on the top of tumor tissue, the ABR waves were affected greatly. Conclusions For the AN patient with preoperative residual hearing, it was necessary to protect hearing by combining continuous auditory monitoring with otoendoscope technique. Based on these efforts the patient could preserve applicable hearing after operation. Whether or not arachnoidal on the top of AN remain and the conditions about blood supplying were the main factors that affect postoperative hearing. Moreover trauma of labyrinthine artery was the key to postoperative hearing loss.