枕下乙状窦后入路内听道后壁磨除的显微解剖

Microsurgical anatomy of drilling posterior wall of the internal acoustic meatus using the suboccipital retrosigmoid approach

目的：观测经枕下乙状窦后入路手术路径中,显微镜下磨除内听道后壁所涉及的重要解剖结构及相关解剖学参数,以指导术中安全磨除内听道后壁。方法模拟枕下乙状窦后入路,对6具（12侧）国人湿性头颅标本显微镜下行磨除内听道后壁,以内听道内口后缘中点（P 点）作为参照点,分别测量 P 点至弓状隐窝、后半规管、共脚、内听道底、前庭导水管外口、颈静脉孔的最短距离,对这些结构拍照记录,所得测量结果行统计学处理。结果以内听道后壁作为参照平面,测得内听道干与后壁平面所呈夹角为47.3＆#176;±17.2＆#176;。以 P 点作为参照点,测得 P 点至弓状隐窝的最短距离（4.10±0.60） mm,P 点至后半规管最短距离（7.39±0.44） mm,P 点至共脚的最短距离（8.09±0.47）mm,P 点至内听道底距离（9.08±0.59）mm,P 点至前庭导水管外口（10.44±0.73）mm,P 点至颈静脉孔最短距离（7.35±1.09）mm。结论枕下乙状窦后入路磨除内听道后壁,其磨除长度不应超过7 mm,可减少半规管及共脚的损伤概率。熟悉磨除内听道后壁过程中容易损伤的结构,可避免损伤半规管、颈静脉球、前庭导水管外口及内淋巴囊等重要解剖结构。

Objective To investigate anatomic characters and obtain microanatomic data for the application of the suboccipital approach drilling of the posterior wall of the internal acoustic meatus （IAM）, in order to open the posterior meatal wall safely and fully. Methods Simulating the procedures of the suboccipital retrosigmoid approach, 12 sides of 6 cadaveric adult head specimens were dissected by using microsurgical anatomic skill, with the posterior meatal walls were drilled. Regard a point P as reference that located posterior to internal acoustic pore, the averaged minimum distances from P to the subarcuate fossae, the posterior semicircular canal, common crus, fundus of IAM, external aperture of vestibular, jugular foramen were measured with the vernier caliper, and then photos were taken. Results Using the posterior wall of IAM as reference plane, the angle between the stem and this plane was 47. 3＆#176; ± 17. 2＆#176;. The average minimum distance from P to the subarcuate fossae, the posterior semicircular canal, common crus, fundus of IAM, external aperture of vestibular, jugular foramen were （4. 10 ± 0. 60） mm, （7. 39 ± 0. 44） mm, （7. 39 ± 0. 44） mm, （7. 39 ± 0. 44） mm, （10. 44 ± 0. 73） mm, and （7. 35 ± 1. 09） mm, respectively. Conclusions To protect the posterior canal and common crus, the length of posterior meatal wall when stripping should be kept within 7 mm. Being familiar with the susceptible structures of the surgical anatomy, such as semicircular canal, external aperture of vestibular, jugular bulb, ect, those structures can be protected very well during microsurgery.