Endoscope-Assisted Suprameatal Exposure through the Retrosigmoid Approach—A Surgical Corridor to the Middle Cranial Fossa and Intrapetrous Internal Carotid Artery: Illustrative Cases and Anatomical Study

Background: The enhanced visualization and illumination provided by the endoscope has heralded the development of various techniques and extensions to the standard retrosigmoid approach.

Objective: Evaluate the efficacy, potential indications and limitations of the suprameatal extension to the endoscopic-assisted retrosigmoid approach.

Methods: Eight sides in four cadaver heads were dissected to study the microsurgical and endoscopic anatomy of the suprameatal region. After drilling the suprameatal tubercle, further bony removal was performed at the petrous apex, exposing the middle cranial fossa dura and the intrapetrous internal carotid artery (C2). In the first illustrative case, a dumbbell-shaped trigeminal schwannoma that straddled both the middle and posterior fossae could be resected thorough this approach. Not only expose the Meckel’s cave but also drill the petrous bone to achieve the wide corridor to middle fossa, this approach was largely effective. The second case was a large chondrosarcoma with extensions around the clivus and petrous bone. Through the same extended suprameatal corridor, exposure of the petrous segment of internal artery (horizontal and vertical segments) allowed the safe resection of the lesion.

Conclusion: Drilling of the suprameatal region is usually considered to widen the exposure around the trigeminal nerve and ganglion in Meckel’s cave. By extending this approach laterally to C2, we can further expose the middle fossa and cavernous sinus region. However, a detailed understanding of the relevant anatomy, especially the location of C2, is critical.