Tailoring the Surgical Corridor to the Basilar Apex in the Pretemporal Transcavernous Approach: Morphometric Analysis of Different Neurovascular Mobilization Maneuvers

Objective: The pretemporal transcavernous approach (PTA) provides optimal exposure and access to the basilar artery; however, a full PTA can be relatively invasive when several vital neurovascular structures are mobilized. The goal of this study is to evaluate the feasibility of different mobilization strategies to plan-tailored approaches to the basilar apex.

Methods: After a full orbitozygomatic craniotomy, ten sides of five cadaveric heads were used to assess the surgical access to the basilar artery via the optico-carotid triangle (OCT), carotid-oculomotor triangle (COT), and oculomotor-tentorial triangle (OTT). Measurements and morphometric analysis were taken for natural neurovascular positions and after each stepwise addition of several expansion maneuvers. A line connecting the midpoints of the limbus sphenoidale and dorsum sellae was used as a reference to normalize measurements of basilar artery exposure and to facilitate the clinical applicability of this technique. Similarly, an imaginary vertical line, the basilometer, along the actual basilar artery and extending up to the mammillary bodies was used to indicate the different segments that could be exposed along the extent of the vessel.

Results: In the OCT, the natural width and maximum width with the ICA lateral mobilization were 4.1 ± 1.62 and 6.3 ± 1.66 mm. The distance from the exposed BA segment to the reference line in a natural position ranged from −1.3 ± 3.94 to +5.7 ± 2.03 mm. In the COT, the natural width, maximum width with the ICA medial mobilization before, after the carotid collar (CC) dissection, and oculomotor nerve lateral mobilization were 6.7 ± 1.81, 8.6 ± 1.79, 9.9 ± 1.84, and 13.1 ± 1.94 mm, respectively. The accessible BA segment ranged from −4.5 ± 2.30 to −1.7 ± 2.95 mm at the natural position. Via the OTT, the natural width and maximum width with the oculomotor nerve medial mobilization were 5.1 ± 1.69 and 8.2 ± 1.60 mm, respectively. The accessible BA segment ranged from −7.1 ± 2.57 to −5.1 ± 2.81 mm at the natural position. In the OCT, COT, and OTT, a posterior clinoidectomy extended the exposure down to −6.2 ± 2.66, −8.2 ± 2.48, and −9.3 ± 2.94 mm, respectively.

Conclusion: This study provides a method to quantitatively evaluate the need for the expansion maneuvers in the PTA to basilar artery aneurysms according to individual anatomical characteristics.

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