Tailored Surgical Access to the Cavernous Sinus and Parasellar Region: Assessment of Cavernous Sinus Entry Corridors and the Periclinoid and Pericavernous Surgical Maneuvers.

Background: Lesions involving the cavernous sinus (CS) represent some of the most challenging pathologies of the skull base owing to the dense traversing and surrounding neurovasculature. Extradural exposure and preparation of this region, whether as initial preparation for a combined intra-extradural approach or as the main avenue of surgical exposure, can enlarge surgical corridors and minimize the need for brain retraction in this very confined space. We provide a detailed assessment of the entry corridors to the CS that are available within each approach, the surgical exposure and freedom provided by each of these corridors, and demonstrate how extradural and intradural preparation of these corridors can be used to widen the available working space and facilitate surgery.

Methods: Pterional, frontotemporal-orbital, frontotemporal-orbitozygomatic, frontotemporal-zygomatic, perilabyrinthine transtentorial, and endoscopic transnasal transsphenoidal approaches were performed on cadaveric heads to access the perisellar and CS regions. Periclinoid maneuvers (extradural cutting of the meningo-orbital band, anterior clinoidectomy, unroofing of the optic canal, opening of the superior orbital fissure, displacement of the extra-annular structures, opening of the annulus of Zinn, and interdural dissection), pericavernous maneuvers (intradural cutting of the distal dural ring, mobilization of the supraclinoid internal carotid artery, opening of the oculomotor porus, and mobilization of cranial nerve (CN) III), peritrigeminal extensions (extradural mobilization of CN V2 [maxillary] and/or V3 [mandibular]), and other surgical maneuvers were performed and evaluated. The CS was divided into 8 anatomical compartments and 9 entry corridors were described, and exposure and freedom were assessed accordingly.

Results: Intradurally, the standard unextended pterional, frontotemporal-orbital, and frontotemporal orbitozygomatic transsylvian approaches provided access solely to the parasellar entry corridor into the superior wall of the CS. Expanding these approaches with extradural periclinoid maneuvers allowed for subsequent application of the intradural pericavernous maneuvers and enlargement of the parasellar corridor and exposure of the carotid cave. Extradurally, the frontotemporal-orbital approach could be expanded via application of periclinoid maneuvers, which provided access to the anterior portions of the main lateral wall entry corridors. The frontotemporal-orbitozygomatic approach could also be expanded with periclinoid maneuvers to provide extradural access to all 6 lateral wall entry corridors. The extradural frontotemporal-zygomatic approach only provided exposure following interdural dissection, which allowed for access to the inferolateral entry corridors into the lateral wall. Extradural peritrigeminal extension in the frontotemporal-orbitozygomatic and frontotemporal-zygomatic approaches allows for enlargement of the supramaxillary and pre- and postmandibular corridors. The perilabyrinthine approach to the posterior wall was enlarged with opening of Dorello's canal and the endoscopic transnasal transsphenoidal approach was enlarged with opening of the optic canal.

Conclusions: Targeted extradural preparation optimizes exposure and significantly improves access to deep-seated targets by enhancing surgical maneuverability through the unlocking of neurovascular structures and widening of surgical corridors without the need for additional brain retraction.