The Transorbital Approach to the Internal Carotid and Middle Cerebral Arteries. A Dissection Study Toward Targeted Access Aneurysm Clipping.

Background: The application of the transorbital (TO) approach for vascular lesions has been scarcely explored. In this anatomic study, we examine the carotid and middle cerebral arteries from the TO perspective and investigate the feasibility of vascular clipping in a pseudovascularized model.

Methods: Three fixed human cadaveric specimens (6 sides) were used for dissection. The sequential TO approach comprised 1) conventional lateral orbital craniectomy; 2) lateral orbital rim removal; and 3) anterior clinoidectomy. The clinoidal, ophthalmic, and communicating carotid segments, branches, related cranial nerves, and dural attachments were examined. Comparison among the 3 variations of bone removal determined the minimal necessary steps for each vascular segment. An additional fresh pseudovascularized specimen (2 sides) was used to test the surgical feasibility of clipping.

Results: The TO approach allowed exposure of the carotid C4 to bifurcation. Clinoidectomy and dural ring opening exposed lateral and dorsal aspects of C5/C6 and the ophthalmic, but not medial or ventral aspects, nor the superior hypophyseal artery or the carotid cave. The posterior communicating artery could be followed from origin to end. The anterior choroidal origin was seen but disappeared behind the uncus. The carotid bifurcation was visible, M1 could be followed to its bifurcation, but A1 lay deep within the field. The corridor permitted arachnoidal dissection, vessel manipulation, and clipping of exposed segments.

Conclusions: The TO approach provides anatomic access to the lateral and dorsal carotid siphon, complete posterior communicating artery, and proximal middle cerebral artery. This preliminary study suggests potential application in the elective treatment of paraclinoid and posterior communicating aneurysms.