Objective: Among the four compartments, the posterior compartment presents the greatest challenges
during endoscopic endonasal surgery, for the reason that, not only its deepest location,
hidden behind the posterior genu of ICA, but also the intricate neuro-vascular-ligamentous
complex it enclosed, which increases the risk of severe complications with even minor
missteps. However, to date, no comprehensive anatomical study has focused on the posterior
compartment of CS. This study aims to delineate the surgical anatomy and technical
nuances for the posterior compartment in the endoscopic endonasal approach.
Methods: Thirty-nine colored-silicone–injected specimens were dissected in this study, in
which nineteen underwent a transcranial approach and twenty underwent an endoscopic
endonasal approach. Three illustrative cases involving the posterior compartment are
included to highlight surgical anatomy and strategies for tumor resection.
Results: From a lateral perspective, the posterior compartment of the CS manifests as an approximately
isosceles triangle, with its apex at the posterior petroclinoid ligament, anterior
boundary at the posterior genu of the ICA, and posterior boundary at the clival dura.
The base of this triangle, representing the widest anterior-posterior dimension of
the posterior compartment, is formed by the petrous process of the sphenoid bone (PPsb)
medially and the petrous apex laterally, measuring 5 ± 0.6 mm. ([Fig. 1A, B]) The posterior parasellar ligament (PPL) was found in 64% of hemispheres, being
the least prevalent compared with other parasellar ligaments. Morphologically, 42%
were typical ligaments with two anchors, with the medial anchor located on the medial
wall of the CS and the lateral anchor on the posterior genu of the ICA ([Fig. 1C, D]); and 58% were net-like, with multiple anchors attaching to various structures within
the posterior compartment. ([Fig. 1E]) Four venous outlets of the posterior compartment, including connection with the
basilar sinus, foramen lacerum, inferior petrosal sinus, and superior petrosal sinus,
were identified ([Fig. 1F]), highlighting the importance of effective hemostasis techniques targeting these
outlets during endoscopic endonasal surgery.
Fig. 1 Microsurgical anatomy of posterior compartment of cavernous sinus.
Conclusion: This study meticulously investigates the anatomical landmarks within the posterior
compartment of the CS, including ligaments, arteries, and venous, which elucidates
the technical nuances essential for tumor resection.
