Torrens M, Maw R, Coakham H, Butler S, Morgan H
Department of Neurosurgery, Ygeia Hospital, Athens, Greece.
Br J Neurosurg. 1994;8(6):655-65. doi: 10.3109/02688699409101179.
The results are presented from a consecutive operative series of 62 acoustic neuromas in 60 patients following the introduction of improved neurophysiological monitoring techniques. Twenty-two patients had usable preoperative hearing. Thirty tumours were less than 2.5 cm diameter and 32 greater in size. Operation was via a 3-4-cm diameter retromastoid craniectomy. The internal auditory meatus was opened by an ENT surgeon (RM) using a drill and the facial nerve identified by stimulation. The tumour was then centrally evacuated by a neurosurgeon (MT/HC) using an ultrasonic aspirator, and the thin exterior part of the tumour carefully dissected off the nerves in or around the capsule with constant stimulation and monitoring of facial EMG, BSAEP and electrocochleography. A new type of stimulation probe has been designed and coupled to a stimulator/integrator/tone burst generator (SB) so that continuous immediate direct feedback to the surgeon is possible. A variable amplitude discriminator rejects baseline EMG (> 50 microV) and a gating circuit prevents stimulus artefact (during monopolar stimulation) from causing interference. By these means the VII nerve could be identified even when translucent and undefinable as a nerve bundle. Anatomical preservation was possible in 98% of VII nerves. Full facial function was present in 20 cases immediately postoperatively. Full delayed recovery occurred in 23 cases giving an eventual total in House Grade I of 69%. Seven other cases recovered to House Grade II. There was therefore 81% satisfactory facial nerve function. This percentage is exactly the same for larger and for smaller tumours. Anatomical preservation of the VIII nerve was achieved in 24/62 (39%) of the whole series and 11/16 (69%) of those with a hearing loss of < 50 dB. Functional preservation of hearing described as usable by the patient (< 65 dB) was achieved in 7/22 cases (32%), 3/13 (23%) in tumours < 2.5 cm and 4/9 (44%) in those > 2.5 cm diameter. Hearing preservation of < 50 dB in patients with preoperative hearing threshold < 50 dB and tumours of < 2.5 cm was 3/11 (27%). Monitoring by BSAEP and ECochG was technically unsatisfactory because the responses were affected by drilling and stimulation. Acoustic nerve preservation should be attempted in all cases with measurable hearing, regardless of tumour size.
在引入改进的神经生理学监测技术后，对60例患者连续进行了62例听神经瘤手术，并展示了相关结果。22例患者术前听力可用。30个肿瘤直径小于2.5厘米，32个肿瘤更大。手术通过直径3 - 4厘米的乳突后颅骨切除术进行。耳鼻喉科医生（RM）使用钻头打开内耳道，通过刺激识别面神经。然后神经外科医生（MT/HC）使用超声吸引器将肿瘤中心内容物吸出，在持续刺激和监测面部肌电图、脑干听觉诱发电位和耳蜗电图的情况下，小心地将肿瘤的薄外部从包膜内或周围的神经上剥离。设计了一种新型刺激探头，并与刺激器/积分器/短纯音发生器（SB）相连，以便能持续即时地向外科医生提供直接反馈。可变幅度鉴别器可排除基线肌电图（>50微伏），门控电路可防止刺激伪迹（单极刺激期间）产生干扰。通过这些方法，即使面神经呈半透明且无法明确为神经束时也能识别。98%的面神经可实现解剖学保留。术后即刻有20例患者面部功能完全正常。23例患者实现了完全延迟恢复，最终House I级的总数为69%。另外7例恢复到House II级。因此，面神经功能满意度为81%。对于较大和较小的肿瘤，该百分比完全相同。在整个系列中，62例中有24例（39%）实现了听神经的解剖学保留，在听力损失<50分贝的患者中，16例中有11例（69%）实现了保留。患者描述为可用（<65分贝）的听力功能保留在7/22例（32%）中实现，肿瘤<2.5厘米的患者中有3/13例（23%）实现，直径>2.5厘米的患者中有4/9例（44%）实现。术前听力阈值<50分贝且肿瘤<2.5厘米的患者中，听力保留<50分贝的比例为3/11（27%）。通过脑干听觉诱发电位和耳蜗电图进行监测在技术上并不理想，因为其反应受钻孔和刺激的影响。对于所有有可测量听力的病例，无论肿瘤大小，都应尝试保留听神经。
