Safe Strategy of Transpetrosal Approach for Tumors around the Petrous Apex

Introduction: Transpetrosal approach for skull base tumors, such as petroclival meningiomas, is more complicated than other approaches. It goes without saying that the pia mater and perforating arteries around the brain stem should be preserved. One of hazardous complications is injury of venous system. Cranial nerve injury also deteriorates quality of life. To make it simpler and safer, the procedure has been arranged.

Materials and Methods: Since 2006 through 2015, we experienced 244 lateral skull base approaches for tumors. Of 244, we performed transpetrosal approach in 34 cases. Preoperative fusion images were made with 3D-CT angiography and MRI (CISS), which was able to detect the veins, arteries, and cranial nerves around tumor. The manner of dural incision was changed individually to preserve venous system. Tumors were removed systematically in the concept of compartmentation into 4 parts. The 1st part consisted of tumor above the IVth nerve. The 2nd was tumor between the IVth nerve and the Vth. The 3rd was between the Vth and VII-VIII complex. The 4th, the last, was below the VII-VIII complex.

Results: We were able to preserve cranial nerves, perforators, and veins without any hazardous complications. No case was deteriorated. Postoperative mean Karnofsky performance status was better than preoperative one (87.4 versus 80.6).

Conclusion: Preoperative imaging, individual dural incision and systematic procedure of tumor removal were very useful in transpetrosal approach for tumors around the petrosal apex.