Expanding the endoscopic transpterygoid corridor to the petroclival region: anatomical study and volumetric comparative analysis.

OBJECTIVE The endoscopic endonasal transmaxillary transpterygoid (TMTP) approach has been the gateway for lateral skull base exposure. Removal of the cartilaginous eustachian tube (ET) and lateral mobilization of the internal carotid artery (ICA) are technically demanding adjunctive steps that are used to access the petroclival region. The gained expansion of the deep working corridor provided by these maneuvers has yet to be quantified. METHODS The TMTP approach with cartilaginous ET removal and ICA mobilization was performed in 5 adult cadaveric heads (10 sides). Accessible portions of the petrous apex were drilled during the following 3 stages: 1) before ET removal, 2) after ET removal but before ICA mobilization, and 3) after ET removal and ICA repositioning. Resection volumes were calculated using 3D reconstructions generated from thin-slice CT scans obtained before and after each step of the dissection. RESULTS The average petrous temporal bone resection volumes at each stage were 0.21 cm3, 0.71 cm3, and 1.32 cm3 (p < 0.05, paired t-test). Without ET removal, inferior and superior access to the petrous apex was limited. Furthermore, without ICA mobilization, drilling was confined to the inferior two-thirds of the petrous apex. After mobilization, the resection was extended superiorly through the upper extent of the petrous apex. CONCLUSIONS The transpterygoid corridor to the petroclival region is maximally expanded by the resection of the cartilaginous ET and mobilization of the paraclival ICA. These added maneuvers expanded the deep window almost 6 times and provided more lateral access to the petroclival region with a maximum volume of 1.5 cm3. This may result in the ability to resect small-to-moderate sized intradural petroclival lesions up to that volume. Larger lesions may better be approached through an open transcranial approach.

Transposition of the paraclival carotid artery: a novel concept of self-retaining vascular retraction during endoscopic endonasal skull base surgery technical report.

BACKGROUND: Fixed retraction of the internal carotid artery (ICA) has previously been described for use during transcranial microscopic surgery. We report the novel use of a self-retaining microvascular retractor for static repositioning and protection of the ICA during expanded endonasal endoscopic approaches to the paramedian skull base. METHODS: The transmaxillary, transpterygoid approach was performed in five cadaver heads (ten sides). The self-retaining microvascular retractor was used to laterally reposition the pterygopalatine fossa contents during exposure of the pterygoid base/plates and the paraclival ICA to expose the petrous apex. Maximum ICA retraction distance was measured in the x-axis for all ten sides. RESULTS: The average horizontal distance of ICA retraction measured at the mid-paraclival segment for all ten sides was 4.75 mm. In all cases, the carotid artery was repositioned without injury to the vessel or disruption of the surrounding neurovascular structures. CONCLUSIONS: Static repositioning of the ICA and other delicate neurovascular structures was effectively performed during endonasal, endoscopic cadaveric surgery of the skull base and has potential merits in live patients.