2025 Poster Presentations
P103: A TRANSTUBERCLE SUPRAMEATAL RETROSIGMOID APPROACH: A NOMENCLATURE BASED ON A MICROSURGICAL TECHNIQUE OF 26 CASES
Mauro A Segura-Lozano, MD, PhD; Aarón G Munguía-Rodríguez; Arturo Santoyo-Pantoja; Mario A Del Real-Gallegos; Alejandro Gonzalez-Silva; Yael R Torres-Torres; Neurología Segura
Introduction: Over the past three decades, various descriptions based on imaging, microsurgical anatomy, and cadaver dissections have been published regarding the internal surface of the petrous apex. These studies highlight its utility in accessing Meckel's cave, the posterior cavernous sinus, the petrous tip, the trigeminal pore, and structures within the cerebellopontine angle. Despite this extensive research, there is no consensus on the nomenclature for identifying the surgical route in question. Therefore, we revised our cases and conducted a literature review to delineate the spatial scope of this approach and propose a simplified nomenclature.
Methods: From January 2020 to June 2024, 626 de novo retromastoid approaches were performed at our institution for primary and secondary trigeminal nerve decompression. We describe the findings of cases that required the transtubercle suprameatal retrosigmoid approach and discuss the importance of this nomenclature.
Results: Among the 626 patients who underwent retromastoid surgery, 26 cases (4.1%) required a transtubercle suprameatal retrosigmoid approach. Of the operated patients, 22 were women and 4 were men, with ages ranging from 26 to 66 years. There were 3 bilateral approaches, 9 right-side approaches, and 14 left-side approaches. The general transtubercular approach is described in Fig. 1.
The microsurgical anatomy of the inner surface of the petrous apex is highly irregular. The suprameatal tubercle is particularly significant for providing a surgical corridor to address various pathologies within the cerebellopontine angle. Generally, it is difficult to predict the obstructiveness of the bony element, so the skull base surgeon must be prepared to extend the retrosigmoid approach if necessary.
According to our experience, the correct nomenclature bust be the “transtubercle suprameatal retrosigmoid approach”. This terminology reflects the precise spatial extent of the approach, distinguishing it from an indefinite spatial extension. The adjective "intradural" is implicit once a retrosigmoid approach with dural opening is performed. The prefix "trans" is crucial because the approach traverses, rather than simply passes over, the suprameatal tubercle. This distinction is particularly important when compared to endoscopic visualization that passes over the tubercle with the lens directed towards the trigeminal pore. In summary, this approach involves an anatomically and microsurgically complex region, necessitating detailed knowledge and careful cadaveric training as part of the skill set for all skull base surgeons.
Fig. 1 Transtubercle suprameatal retrosigmoid approach.
(A) Suprameatal tubercle obstructing visualization of the CN V. (B) A 2 mm diamond burr drilling the cortical bone. (C) The 4 mm burr is used when reaching the spongy bone. (D) The 4 mm burr is used again to drill the opposite cortical bone. (E) Exposition of the surgical corridor and exploration on the CN V. (E) Colocation of Teflon felt.
Conclusion: An experienced skull base surgeon should be trained in the cadaver shop and have sufficient microsurgical tools to make the intraoperative decision in a specific clinical situation, whether for primary trigeminal neuralgia or trigeminal neuralgia secondary to a petrous apex tumor.