Introduction: Extended retrosigmoid approach is an anternative way to classical presigmoid approach and has less morbidity. The extended retrosigmoid provides additional Access to ventral brain stem by drilling mastoid bone and sigmoid sinus skeletonized. In this study we compared classical retrosigmoid and extended retrosigmoid approaches and detailed surgical anatomy of the extended retrosigmoid approach was presented.
Methods: 5 formalin fixed adult cadaveric heads were used. Theheads were scanned with CT and MRI before dissection and after dissection completed. Both classical retrosigmoid and extended retrosigmoid approacehs were done and documented each step. The angle of view was compared by measuring the angle. The base of the angle located at the entrance of internal acustic meatus and the borders pass at each craniotomy borders.
Results: The mean difference between angle of view between retrosigmoid and extended retrosigmoid approach was 15.40 . And this difference provided wider corridor to approach cerebellopontine angle and ventral brain stem. Another useful landmark is asterion. It is almost allways located over the inferior border of the transvers sinus and the junction of transvers and sigmoid sinus is 10-25mm lateral to asterion.
Conclusions: Extended retrosigmoid approach allows Access the entire cerebellopontine angle extending from tentorium to the foramen magnum with minimal cerebellar retraction. This approach decreased the need of presigmoid approach and has less morbidity.
Patient Care: This approach is an easy way compared to presigmoid approach and has less morbidity
Learning Objectives: By coclusion of this session participitans should be able to 1)describe the detail anatomy of the cerebellopontin angle 2)Clinical importance of extended retrosigmoid approach 3)Compare the difference between clasiccal retrosigmoid and extended retrosigmoid approach.