目的　医源性面神经损伤是中耳乳突手术的严重并发症之一，面神经椎曲段成为当前最容易受损伤的部位，这些案例中，部分患者存在面神经椎段外凸畸形，使得在乳突切除过程中，面神经位置高于水平半规管平面，我们通过活体解剖观察和高分辨率颞骨CT检查，揭示汉族人群面神经椎段外凸畸形的发生率，为更安全地开展耳科手术提供解剖学资料。  方法　2005年4月-2011年4月在我科接受单侧面神经减压术的302名成年汉族周围性面瘫患者，在手术显微镜下，观察分析面神经椎段外凸畸形的情况。对比术前高分辨率CT检查，探讨CT在发现这种畸形的价值。   结果    14例患者术中发现有面神经椎曲段外凸畸形，占全部患者的4.6%。术前颞骨CT的轴位平扫只发现其中1例有这种畸形，而冠状位重建可以100%在术前诊断出这种畸形。  结论　汉族人群中面神经椎曲段外凸畸形并不罕见。术前颞骨高分辨率CT的冠状位重建能发现患者是否存在这种畸形，应列为乳突手术前的常规检查。在乳突切除术中，以水平半规管平面作为安全解剖深度平面的这一传统技巧在汉族人群并不可靠，存在医源性面神经损伤的风险。

Objectives　To reveal the occurrence rate of extrusion abnormality at pyramid segment of facial nerve by observation on vivisection and high-resolution CT scanning of temporal bone, and provide anatomic data for safer development of otologic surgery.　Methods　Extrusion abnormality at pyramid segment of facial nerve among 302 adult Han cases with peripheral facial palsy, who received unilateral facial nerve decompression surgery in our department from April, 2005 to April, 2011, was observed and analyzed under operating microscope. The value of CT in the discovery of the abnormality was evaluated by the comparison of preoperative high-resolution CT data.　Results　Extrusion abnormality at pyramid segment of facial nerve was found to be presented among 14 cases during the surgery, accounting for 4.6% among all cases. Only one case with such abnormality was discovered by preoperative axial CT scanning of temporal bone, while 100% of the abnormality could be found by coronal reconstruction preoperatively.　Conclusions　Extrusion abnormality at pyramid segment of facial nerve is available among 4.6% Han adults. High-resolution CT scanning of temporal bone should be performed routinely prior to mastoid surgeries, and it's necessary to perform coronal reconstruction to find such abnormality. During mastoidectomy, the traditional skill with horizontal semicircular canal plane as the deep plane for safe dissection is not reliable for Han population, with the risk of iatrogenic facial nerve injury.