The retrosigmoid intradural petrous apex approach (RIPA) to Meckelʹs cave and middle fossa

Introduction: The authors present a modification of the standard retrosigmoid intradural route to cerebellopontine (CPA) tumors which extend into Meckelʹs cave and the middle cranial fossa. This approach is called by the authors “Retrosigmoid Intradural Petrous Apex Approach” (RIPA). The surgical anatomy of the RIPA is presented along with clinical examples. Methods: Main steps for the RIPA include a standard retrosigmoid craniotomy, intradural exposure of CPA, drilling the petrous apex portion to expose the Vth nerve within the Meckelʹs cave, and opening the tentorium up to Meckelʹs cave. The RIPA has been routinely used in our Department since 1994. A total of 16 patients harboring meningiomas and trigeminal schwannomas which affected the middle and posterior fossae and Meckelʹs cave have been operated on using this approach. The surgical anatomy is described by cadaveric dissection, and the 16 clinical cases are reviewed. Clinical and operative records, as well as radiological findings and postoperative outcome are presented. Results: Total tumor resection with preservation of the cranial nerves V, VII, VIII was achieved in the majority of the cases. No mortality and minimal morbidity characterized this series. Conclusion: The RIPA allowed for resection of large tumors from the posterior fossa up to the middle fossa using a simple approach without necessity of extensive transpetrosal exposures. Facial and cochlear nerves are well visualized and preserved in the majority of the cases.