ABSTRACT
As the internal carotid artery [ICA] traverses the skull base and the cavernous sinus to become an intradural structure, its course can be altered by lesions originating from or extending to these regions. The identification of this altered course as visualized on magnetic resonance imaging [MRI] help in preoperative recognition of these lesions and consequent surgical planning. The internal carotid artery was encased and narrowed in three intracavernous meningiomas, one hemangiopericytoma, and nine sphenoid wing and petrodival meningiomas invading the cavernous sinus. Tumors of the lateral wall of the cavernous sinus, [seven trigeminal neurinomas, two epidermoids, and one melanoma] displaced the internal carotid artery medially without encasement or narrowing. Chondrosarcoma invading the cavernous sinus [five cases], petrous apex cholesteatoma [three cases], and petrous apex cholesterol granuloma [two cases] displaced the ICA laterally and anteriorly. Pituitary tumors invading the cavernous sinus [seven cases] displaced the ICA laterally in medial compartment invasion with encasement and narrowing in advanced invasion. Displacement of the ICA on MRI is a useful diagnostic sign