Colletti V, Fiorino F G, Carner M, Tonoli G
ENT Department, University of Verona, Italy.
Otolaryngol Head Neck Surg. 1997 Dec;117(6):596-605. doi: 10.1016/S0194-59989770039-1.
Hearing loss during removal of acoustic neuroma (AN) may be due to labyrinthine and/or neural and/or vascular damage. Surgical maneuvers relating to perioperative and postoperative hearing may give rise to mechanisms of auditory impairment. Recording action potentials from the intracranial portion of the cochlear nerve (CN) has proven particularly useful for identifying the mechanisms of iatrogenic auditory injury. In this paper intraoperative and postoperative auditory impairments are investigated in relation to surgical steps in a group of 47 subjects with AN (size ranging from 5 to 25 mm) undergoing removal by a retrosigmoid-transmeatal approach. Drilling of the internal auditory canal (IAC), removal of the AN from the IAC fundus, coagulation close to the CN, lateral to medial tumor traction, separation of the CN from the facial nerve, and stretching of the CN have proven to be the most critical surgical steps in hearing preservation. On the other hand, maneuvers such as intracapsular tumor removal, vestibular neurectomy, suction close to the AN, and closure of the IAC defect did not correlate with changes in auditory potentials. Predisposing factors to postoperative hearing deterioration were IAC enlargement greater than 3 mm, IAC tumor size greater than 7 mm, extracanalar tumor size greater than 20 mm, labyrinth medial to the IAC fundus, severe involvement of the CN in the IAC, preoperative abnormal auditory brainstem responses, and normal vestibular reflectivity. Age and preoperative hearing did not prove to be statistically related to postoperative hearing. The variations in morphology and latency of CNAPs are discussed in relation to the mechanisms of iatrogenic injury.
听神经瘤（AN）切除术中听力丧失可能是由于迷路和/或神经和/或血管损伤。与围手术期和术后听力相关的手术操作可能会引发听觉损伤机制。记录耳蜗神经（CN）颅内部分的动作电位已被证明对识别医源性听觉损伤机制特别有用。本文研究了一组47例AN（大小范围为5至25mm）患者经乙状窦后 - 经耳道入路切除术中及术后与手术步骤相关的听觉损伤。事实证明，钻开内耳道（IAC）、从IAC底部切除AN、靠近CN进行电凝、从外侧向内侧牵引肿瘤、将CN与面神经分离以及拉伸CN是听力保留中最关键的手术步骤。另一方面，诸如囊内肿瘤切除、前庭神经切除术、靠近AN进行吸引以及封闭IAC缺损等操作与听觉电位变化无关。术后听力恶化的易感因素包括IAC扩大超过3mm、IAC肿瘤大小超过7mm、外耳道外肿瘤大小超过20mm、IAC底部内侧的迷路、IAC中CN的严重受累、术前听觉脑干反应异常以及正常的前庭反射率。年龄和术前听力在统计学上与术后听力无关。本文还结合医源性损伤机制讨论了CNAPs形态和潜伏期的变化。
