Anatomical Study For Microsurgery Of Extended Retrosigmoid Approach

Part 1: Anatomical study for microsurgery of extended retrosigmoid approachObjective To investigate the improvement of surgical field exposure in cerebellopontine angle area via the extended retrosigmoid approach by microanatomical study. Methods Suboccipital retrosigmoid approach was used on 10 adult fresh cadaveric heads(20 sides) and then the extended retrosigmoid approach was simulated by further revealing the transverse sinus and sigmoid sinus. Using internal auditory meatus,the entrance of Meckel's cave and midpoint of clivus as reference points respectively, the maximum angles and distances between superior and inferior border,lateral and medial border of bone window and the three reference points were measured in two approaches. Then,the exposure of vital nerve and blood vessels in the cerebellopontine angle area via the extended retrosigmoid approach was observed. Results In extended retrosigmoid approach,the distances between midpoint of lateral border of bone window and three reference points were shorter than that in suboccipital retrosigmoid approach(all P<0.05).The maximum angles between both superior and inferior border of bone window and the reference points were increased significantly,and did also the maximum angles between both lateral and medial border of bone window and the reference points in extended retrosigmoid approach(all P<0.05). Conclusion The extended retrosigmoid approach can increase the extent of surgical exposure,expand the visual angle of operation,improve the total resection rate of large tumors,and protect the vital nerves and blood vessels in the cerebellopontine angle area. Part 2: The clinical application of the extended retrosigmoid approachObjective To explore the clinical effect and safty of surgical skills in microsurgical resection of large cerebellopontine angle lesions via the extended retrosigmoid approach.Methods Seventeen cases of large cerebellopontine angle lesions treated by microsurgery via the extended retrosigmoid approach were retrospectively analyzed in operation field, microsurgical techniques,intraoperative accidents, and management of the postoperative complications.Doppler ultrasound was used to monitor the blood flow of transverse sinus and sigmoid sinus during operation. Results The tumors were totally removed in 14 cases and subtotally in 3 cases.The facial nerve function was well preserved in 14 cases and the hearing was preserved in 5 cases.Heart rate decreased in 3 cases during operation,and 2 patients suffered from short-term postoperative complications,but no death occurred.Bblood flow of transverse sinus and sigmoid sinus were patency without thrombosis. Conclusion Complications and mortality of microsurgical resection of large cerebellopontine angle lesions via the extended retrosigmoid approach are low. Good clinical effect was observed.Proficient microsurgical skills and thorough understanding of the microanatomy are crucial for total tumor resection and reduction of the nerve injury and surgical complications.