显微镜下骨锚式助听器植入术和适宜植入部位的初步研究

Position and operation skill of bone-anchored hearing aids implantation under microscopy

目的探讨局麻下通过显微镜进行骨锚式助听器(BAHA)植入手术的优点,总结植入的适宜部位。方法选择2例男性患者,①62岁患者为左耳混合性聋,右耳极重度感音神经性聋(近全聋),气导左耳为92.5 dB,右耳>100 dB(取0.5、1、2、4 kHz均数,当听阈>100 dB时仍作100 dB,下同),声场检查双耳均大于100 dB,声场软带BAHA试验45～100 dB下降斜坡型,4 kHz以上消失。BAHA植入部位选择在耳后沟后3 cm,外耳道口上缘水平上方2.5～3.0 cm处,距外耳道口约5.0～5.5 cm植入基座;②16岁患者为双耳传导性耳聋,曾先后行鼓室成形听骨链重建术,均因3听骨畸形固定,术后听力提高不明显。声场检查50～70 dB水平型(左耳为67.5 dB,右耳为52.5 dB),声场软带BAHA试验40～50 dB,水平型。BAHA植入部位选择外耳道口上缘平面、耳后沟后2 cm距外耳道口约4.5～5.0 cm处。结果带机后声场检查结果,病例1术耳平均57.5 dB,对侧耳平均72.5 dB;曲线呈水平型,且双侧4 kHz亦测出,术侧较术前平均提高35 dB,对侧耳平均提高27.5 dB,较术前试戴结果术侧也平均提高26.25 dB;病例2术耳32.5 dB,曲线呈水平型,较术前声场检查术侧平均提高35 dB,比术前软带试验结果也平均提高13.75 dB。2例术后3个月复查CT均显示骨融合良好。三维重建显示,病例1钛钉虽未穿入颅骨中,但局部向颅内突起。病例2见钛钉远端离颅内面至少有2 cm的距离。结论 BAHA对改善传导性耳聋及独耳患者听力效果确切,局麻下显微镜手术一般可以适用。耳道正后方乳突骨质较厚,比传统耳道后上方植入基座产生颅内损伤机率更少。

Objective To explore bone-anchored hearing aids（BAHA） implant position and operation skill under local anaesthesia microscopy. Methods Both 2 male patients were operated under microscopy and local anaesthesia. One was 62 years old. He had the mixed hearing loss at the left and sensorineural deafness at the right. The result of sound field examine was over 100 dB in two ears, and the BAHA soft belt test was 45-100 dB sharp decline type, over 4 kHz was lost. In case 1, the BAHA pedestal was implanted in the conventional position on the skull, which was behind the ear groove 3 cm and above the ear canal 3 cm. The two was 16 years old. He had double three-auditory-ossicle mal- formed fixation and hearing loss, but the hearing was only a little improved after operation of two times. The result of sound field audiometry was 67.5 dB, and the BAHA soft belt test was 40-50 dB fiat type. In case 2, the BAHA pedes- tal was implanted on the different position on the skull, which was in the level of the ear canal and behind the ear groove about 2 cm. Results Case 1 obtained the hearing improved about 35 dB in the sound field examine post-operation. Case 2 hearing improved above 35 dB. The post-operative CT revealed Case 1 pedestal had a little projecting skull bone into meninges. Case 2 pedestal was away from meninges about 2 cm. Conclusion BAHA can evidently improve hear- ing, and the pedestal can be implanted under local anaesthesia and microscopy in most cases. Bone is thicker at the po- sition behind the ear canal than at the conventional position, so pedestal implantation at this position has less probability of damage mininges than the conventional position.