Pictorial Review of the Microvasculature Arising from the Cavernous Segment of the ICA (C4), and the Venous Connections of the Cavernous Sinus

Background Endonasal endoscopic microsurgery within the cavernous sinus and adjacent regions requires a sound understanding of the related microanatomy to prevent neurovascular compromise. Although there is vast literature on the microvasculature of the cavernous sinus for the transcranial approaches, few studies covered the endonasal perspective and no study correlated transcranial and endoscopic anatomy with multimodal imaging including angiography. In this study, we aim to provide a detailed, richly illustrated description of the microvasculature arising from the cavernous ICA and the venous connections of the cavernous sinus. Our comparative analysis and the correlation with angiographic data of selected clinical cases might advance the understanding of this complex anatomy and help in preventing neurovascular complications in endoscopic, microsurgical, and endovascular procedures.

Methods Eighteen formalin-fixed, colored, silicone-injected anatomical specimens were dissected endoscopically, another 10 similar specimens were used for microscopic dissection of the cavernous sinus and the adjacent perisellar and clival regions. For illustration, multimodal imaging (supraselective digital subtraction angiography [DSA], CT/CTA, MRI/MRA) was reviewed for selected cases of sphenocavernous, tentorial, and petroclival meningiomas, as well as AV fistulas in which the arterial microvasculature arising from the cavernous ICA could be identified.

Results The cavernous segment of the ICA (C4, van Loveren classification) spans from the petrolingual ligament to the proximal dural ring. At the medial loop (as described by Dolenc), it gives rise to the meningohypophyseal trunk, which usually branches into the inferior hypophyseal, dorsal meningeal, and marginal tentorial (“Bernasconi-Cassinari”) arteries. The inferolateral trunk arises slightly more distally from the horizontal subsegment and its branches consistently course between the abducens nerve and the ophthalmic division of the trigeminal nerve. There are numerous inconsistent anastomoses between the cavernous branches of the middle and accessory middle meningeal arteries, and the clival and petrosal branches of the ascending pharyngeal artery. Similarly, the presence and number of McConnell's capsular arteries is widely variable. The venous contribution to and drainage from the cavernous sinus was found to be largely consistent for the ophthalmic vein, sphenoparietal, petrooccipital, carotid, superior and inferior petrosal sinuses, and the emissary veins of the foramina rotundum and ovale. Constant, but widely variable in their morphological extension, are the basilar sinus (or “transverse and posterior occipital sinus”) and the intercavernous connections (or “superior, inferior, and posterior intercavernous sinus,” also termed “coronary sinus”). Some smaller inconsistent emissary veins could be identified, for example, the emissary vein of the sphenoidal foramen (or “vein and foramen of Vesalius”), located in the anterior aspect of the mandibular strut.

Conclusion We provide an anatomical description of the microvasculature arising from the cavernous segment of the ICA (C4), and the venous connections of the cavernous sinus from both the endonasal endoscopic and the open transcranial perspective.

Fig. 1