Small Sphenoid Ridge as a Factor Associated with Laterally Deviated Proximal Sylvian Fissure in Patients Undergoing Pterional Craniotomy

Abstract

Background: During the pterional-transsylvian approach, we sometimes encounter the proximal Sylvian fissure (SF) deviating laterally beyond the fold of the sphenoidal ridge (SR) and experience difficulty dissecting the SF due to the deep and oblique dissection plane. In the present study, we explored the association between the height of the SR and lateral deviation of the SF during the pterional-transsylvian approach.

Methods: The association between the height of the SR on axial computed tomography and the presence of a laterally deviated SF was evaluated by reviewing patients who had undergone pterional craniotomy.

Results: Among the 52 patients included, lateral deviation of the SF was observed in 8 patients (13.4%). The median height of the SR was significantly smaller in patients with laterally deviated SF (6.0 mm) than in patients with non-deviating SF (13.4 mm; P < 0.0001). The oculomotor nerves and middle fossa were observed at the edge of the dissection plane of the SF in all patients with a laterally deviating SF, while medial structures such as the internal carotid artery or optic nerve were observed in patients with non-deviating SF.

Conclusions: Small SR was associated with lateral deviation of the proximal SF.

Keywords: Anatomy; Pterional craniotomy; Sphenoid ridge; Sylvian fissure.