Abstract: Objective A microanatomical study was performed to observe the relationship between trigeminal nerve, superior cerebellar arteries (SCA) and superior petrosal veins (SPV), in order to provide anatomical reference for the clinical application of microvascular decompression. Methods Simulating operation technique, a retrosigmoid keyhole craniotomy was made and the bone window was controlled within 2.00 cm × 2.50 cm. Thirty sides of 15 cadaver heads (embalmed and injected) were dissected under 4 to 24 magnification via operating microscope. Opened the calvaria and removed dura mater and cerebrum tissue, the tentorium of cerebellum and brainstem were exposed. Trigeminal nerve, SCA and SPV were dissected carefully under microscope. The related anatomical variations were observed and analysed. Results Retrosigmoid keyhole approach presented a clear visualization of trigeminal nerve, trochlear nerve, SPV, and SCA and the branches. The site and the route of cranial nerves were regular, the vascular structures were somewhat variable related to nerves which can be contacted or compressed. SCA of 11 specimens (36.67%) contacted with trigeminal nerve. The suprameatal tubercle was developed variably, but in all specimens it obstructed the exposure of Meckel's cavity under microscope. Of the 30 superior petrosal sinus (SPS) examined in 15 cadaver heads, the SPV entered into the sinus as a single venous stem in 24 sides and as 2 stems in the remaining 6 sides. There were 22.22% (8/36) of SPV entered into SPS at the lateral side of the medial margin of internal auditory meatus (IAM), 63.89% (23/36) of the SPV entered into the SPS between the medial margin of the IAM and the lateral margin of the trigeminal nerve of Meckel's cavity, and 13.89% (5/36) of the SPV entered into the SPS at a point medial to the lateral margin of the trigeminal nerve. Five different types were identified based on the relative sites between trigeminal nerve and SPV, including noncontact type, contact type, branch riding type, arachnoid adhesion type and perforating nerve type. Conclusion The SCA and SPV have close relationship with trigeminal nerve. Compression of the SCA is the primary etiological factor for trigeminal neuralgia in most cases. SPV is the most frequently encountered venous structure during microvascular decompression operation and exists significant variation in position, form, branch and distribution area. Maneuvering the SPV individually may aid surgical exposure and may reduce the probability of potential venous complications.

Key words: Trigeminal nerve, Cerebral veins, Microsurgery, Neuroanatomy

摘要： 目的   显微解剖观察三叉神经、小脑上动脉与岩静脉之间的解剖关系，以为微血管减压术提供解剖学参考。方法   模拟经乙状窦后锁孔入路手术对15 例（30 侧）成人尸头标本进行解剖，骨窗范围设计为2.00 cm × 2.50 cm，于4 ~ 24 倍手术显微镜下观察显露范围和解剖结构，打开颅盖骨、剔除硬脑膜和大脑组织，显露小脑幕和脑干，通过显微镜解剖三叉神经、小脑上动脉和岩静脉，观察分析相关解剖学变异。结果   经乙状窦后锁孔入路行微血管减压术可较好地显露三叉神经、滑车神经、岩静脉和小脑上动脉。约36.67％（11/30）标本小脑上动脉与三叉神经接触或压迫，15 例标本内听道上结节形态变异较大，阻挡了对Meckel憩室的显露。其中单干型岩静脉24 侧，双干型岩静脉6 侧；约22.22％（8/36）岩静脉在内听道内侧缘外侧部汇入岩上窦，63.89％（23/36）在内听道内侧缘与Meckel 憩室处三叉神经外侧缘之间汇入岩上窦，13.89％（5/36）于三叉神经外侧缘以内汇入岩上窦。三叉神经与岩静脉相对位置关系分为无接触型、接触型、属支“骑跨”型、蛛网膜粘连型和贯穿神经型。结论   小脑上动脉和岩静脉与三叉神经解剖关系密切，是三叉神经痛的主要责任血管。岩静脉是微血管减压术中必须显露的血管结构，其位置、形态、分支和静脉回流区域存在明显变异，个体化处理岩静脉，有助于手术视野的显露，减少静脉系统并发症。

关键词: 三叉神经, 脑静脉, 显微外科手术, 神经解剖学