Anterior Petrosectomy With Intertentorial Approach

Abstract

Background and objectives: The extradural anterior petrosal approach (EAPA) can present a challenge because it deals with critical structures in a narrow, confined corridor. It is associated with several potential approach-related risks including temporal lobe and venous injuries. Tentorial peeling has the potential to largely eliminate these risks during the approach and may offer more options for tailoring the dural opening to the anatomic region that one wants to expose.

Methods: Anatomic dissections of five adult injected non-formalin-fixed cadaveric heads were performed. Anterior petrosectomy with intertentorial approach (APIA) through a tentorial peeling was completed. Step-by-step documentation of the cadaveric dissections and diagrammatic representations are presented along with an illustrative case.

Results: Tentorial peeling separates the tentorium into a temporal tentorial leaf and posterior fossa tentorial leaf, adding a fourth dural layer to the three classic ones described during a standard EAPA. This opens out the intertentorial space and offers more options for tailoring the dural incisions specific to the pathology being treated. This represents a unique possibility to address brainstem or skull base pathology along the mid- and upper clivus with the ability to keep the entire temporal lobe and basal temporal veins covered by the temporal tentorial leaf. The APIA was successfully used for the resection of a large clival chordoma in the illustrative case.

Conclusion: APIA is an interesting modification to the classic EAPA to reduce the approach-related morbidity. The risk reduction achieved is by eliminating the exposure of the temporal lobe while maintaining the excellent access to the petroclival region. It also provides several options to tailor the durotomies based on the localization of the lesion.

FIGURE 1.

Schematic drawing representing the surgeon's view after completing anterior petrosectomy A, with and B, without tentorium peeling. B, The drawing highlights the variation of dural opening (APIA 1-4) made possible by this approach that allows it to be specifically tailored to the patient and pathology being treated. AE, Arcuate eminence; APIA, anterior petrosectomy with intertentorial approach; GSPN, greater superficial petrosal nerve; IPS, inferior petrosal sinus; MMA, middle meningeal artery; PD, posterior fossa dura; PFTL, posterior fossa tentorial leaf; pICA, petrosal internal carotid artery; SPS, superior petrosal sinus; TD, temporal dura; TTL, temporal tentorial leaf; V3, mandibular branch of trigeminal nerve.

FIGURE 2.

Schematic drawing illustrating tentorial peeling and the most important anatomic landmarks. Coronal view A, before and B, after anterior petrosectomy and peeling have been performed. The plane between the TTL (pink line) and the PFTL (brown line) is developed just superior to the SPS. A and B, were used with permission from Giammattei, L., Starnoni, D., Ronconi, D. et al, “Tentorial peeling during combined petrosal approach: a cadaveric dissection.” Acta Neurochirurgica. 164, 2833-2839, 2022, Springer Nature. DOI: https://doi.org/10.1007/s00701-022-05370-z. PFTL, posterior fossa tentorial leaf; PD, presigmoid dura, SPS, superior petrosal sinus; TD, temporal dura; TTL, temporal tentorial leaf.

FIGURE 3.

A, Schematic drawing representing the surgeon's view obtained after APIA 1 dural cut. B, View obtained with APIA 1 + 2 dural cuts. C, View obtained with APIA 1 + 2+3 dural cuts where Meckel's Cave has been opened. D, View obtained with APIA 1 + 2+3 + 4 dural cuts. AE, arcuate eminence; APIA, anterior petrosectomy with intertentorial approach; GSPN, greater superficial petrosal nerve; IPS, inferior petrosal sinus; MMA, middle meningeal artery; PD, posterior fossa dura; PFTL, posterior fossa tentorial leaf; pICA, petrosal internal carotid artery; SPS, superior petrosal sinus; TD, temporal dura; TTL, temporal tentorial leaf; V3, mandibular branch of trigeminal nerve.

FIGURE 4.

A, Surgeon's view after completion of an anterior petrosectomy and tentorial peeling. B, Magnified view of Kawase's triangle with tentorial peeling, showing the APIA dural cuts 1–4. C, View obtained after APIA 1 dural cut. D, View obtained with APIA 1 + 2 dural cuts. AICA, anterior inferior cerebellar artery; APIA, anterior petrosectomy with intertentorial approach; GSPN, greater superficial petrosal nerve; ICA, internal carotid artery; IPS, inferior petrosal sinus; LPZ, lateral pontine zone; PD, posterior fossa dura, PFTL, posterior fossa tentorial leaf; SCA, superior cerebellar artery; SPS, superior petrosal sinus; STZ, supratrigeminal zone; TD, temporal dura; TTL, temporal tentorial leaf; V3, mandibular branch of trigeminal nerve.

FIGURE 5.

A, Meckel's cave has been opened after the APIA 3 cut, allowing transposition of the fifth cranial nerve. B, Transposing the fifth nerve superiorly improves exposure of the basilar trunk and middle clivus. C, APIA 4 cut is made by crossing across the PFTL and incisura, into the TTL, and then advancing anteriorly into the temporal dura posterior and superior to the cavernous sinus. D, Operative view obtained after all four APIA cuts have been completed. The temporal lobe is completely covered with dura. AICA, anterior inferior cerebellar artery; APIA, anterior petrosectomy with intertentorial approach; LPZ, lateral pontine zone; SCA, superior cerebellar artery; STZ, supratrigeminal zone; TD, temporal dura; TTL, temporal tentorial leaf; V3, mandibular branch of trigeminal nerve.

FIGURE 6.

A, Preoperative axial T2-weighted and B, sagittal gadolinium–enhanced magnetic resonance imaging showing a large petroclival intradural lesion, extending inferiorly to the level of the prepontine cistern and the internal acoustic meatus and superiorly to the level of the interpeduncular cistern and the upper margin of the dorsum sella with significant compression of the pons. C, Postoperative axial and D, sagittal gadolinium–enhanced magnetic resonance imaging showing a near total resection with a small residual tumor at the level of the uppermost margin of the dorsum sellae dura.