Dardinger Microneurosurgical Skull Base Laboratory, Department of Neurological Surgery, The Ohio State University Medical Center, Columbus, Ohio 43210, USA.
Neurosurgery. 2009 Dec;65(6 Suppl):53-9; discussion 59. doi: 10.1227/01.NEU.0000343521.88537.16.
Hearing loss after removal of vestibular schwannomas with preservation of the cochlear nerve can result from labyrinthine injury of the posterior semicircular canal and/or common crus during drilling of the posterior wall of the internal auditory meatus. Indeed, there are no anatomic landmarks that intraoperatively identify the position of the posterior semicircular canal or of the common crus. We investigated the usefulness of image guidance and endoscopy for exposure of the internal auditory canal (IAC) and its fundus without labyrinthine injury during a retrosigmoid approach.
A retrosigmoid approach to the IAC was performed on 10 whole fresh cadaveric heads after acquiring high-resolution computed tomographic scans (120 kV; slice thickness, 1 mm; field of vision, 40 cm; matrix, 512 x 512) with permanent bone-implanted reference markers. Drilling of the posterior wall of the IAC was executed with image guidance. Its most lateral area was visualized using endoscopy.
Target registration error for the procedure was 0.28 to 0.82 mm (mean, 0.46 mm; standard deviation, 0.16 mm). The measured length of the IAC along its posterior wall was 9.7 +/- 1.6 mm. The angle of drilling (angle between the direction of drill and the posterior petrous surface) was 43.3 +/- 6.0 degrees, and the length of the posterior wall of the IAC drilled without violating the integrity of the labyrinth was 7.2 +/- 0.9 mm. The surgical maneuvers in the remaining part of the IAC, including the fundus, were performed using an angled endoscope.
Frameless navigation using high-resolution computed tomographic scans and bone-implanted reference markers can provide a "roadmap" to maximize safe surgical exposure of the IAC without violating the labyrinth and leaving a small segment of the lateral IAC unexposed. Further exposure and surgical manipulation of this segment, including the fundus without additional cerebellar retraction and labyrinthine injury, can be achieved using an endoscope. Use of image guidance and an endoscope can help in exposing the entire posterior aspect of the IAC including its fundus without violating the labyrinth through a retrosigmoid approach. This technique could improve hearing preservation in vestibular schwannoma surgery.
在经迷路切除前庭神经鞘瘤时，若在内耳迷路后骨半规管和/或共同管处的后颅窝侧壁钻孔时损伤迷路，可能导致术后听力丧失。事实上，术中没有解剖标志可以确定后骨半规管或共同管的位置。我们研究了图像引导和内窥镜用于显露内听道（IAC）及其底部而不损伤迷路的在后乙状窦入路的效果。
在获取带有永久性骨植入参考标记的高分辨率计算机断层扫描（120 kV；层厚 1 毫米；视野 40 厘米；矩阵 512 x 512）后，对 10 个全新鲜尸体头颅进行了后乙状窦入路 IAC 显露。在内耳迷路后骨半规管的后侧壁进行钻孔时使用了图像引导。使用内窥镜观察其最外侧区域。
该手术的靶区注册误差为 0.28 至 0.82 毫米（平均值 0.46 毫米；标准差 0.16 毫米）。沿 IAC 后侧壁测量的 IAC 长度为 9.7 +/- 1.6 毫米。钻孔角度（钻头方向与后岩骨表面之间的角度）为 43.3 +/- 6.0 度，且不破坏迷路完整性而钻通的 IAC 后侧壁长度为 7.2 +/- 0.9 毫米。在内耳迷路其余部分的手术操作，包括底部，使用角度内窥镜进行。
使用高分辨率计算机断层扫描和骨植入参考标记的无框架导航可以提供“路线图”，以最大限度地安全暴露 IAC 而不损伤迷路，并使一小段外侧 IAC 不暴露。使用内窥镜，可以进一步暴露和手术操作该段，包括不进行额外的小脑牵拉和迷路损伤的底部。图像引导和内窥镜的使用有助于通过后乙状窦入路暴露包括底部在内的整个 IAC 后侧面，而不损伤迷路。这种技术可以提高前庭神经鞘瘤手术中的听力保护。
