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Figure 4: Case 1: (a) The coring the anterior clinoid process (ACP) from within its bony shell is done using a 3-4mm diamond drill. This is helpful in drilling out the posterior strut of anterior clinoid process (ACP). #: Drilled planum sphenoidale; II: Optic nerve; ICA: Internal carotid artery; CS: Cavernous sinus. (b) The last portion of the posterior root (optic strut) of the anterior clinoid process (ACP) is being drilled, thereby mobilizing the ACP. #: Drilled planum sphenoidale; II: Optic nerve; ICA: Internal carotid artery; CS: Cavernous sinus. (c) The mobilized shell of anterior clinoid process (ACP) is gently dissected off from the carotid collar (CC), the fascial layer covering the clinoidal segment of internal carotid artery. #: Drilled planum sphenoidale; II: Optic nerve; ICA: Internal carotid artery; CS: Cavernous sinus. D: Removal of the anterior clinoid process by drilling its anterior strut (the portion between the planum sphenoidale (#) and anterior clinoid process; and, also its posterior strut (the core of the anterior clinoid process) exposes the distal dural ring (DDR), the proximal dural ring and the carotid collar [CC; the fascia covering the proximal clinoidal segment of the internal carotid artery (ICA)], as the internal carotid artery (ICA) curves laterally to enter the cavernous sinus (CS). The junction of distal cavernous sinus dura and the thickened proximal aspect of the carotid collar forms the proximal dural ring. The drilling of the planum sphenoidale (#) over the roof of optic foramen has exposed the distal part of optic nerve (II). The latter may gently be mobilized medially to access the proximal aspect of neck of the aneurysm. (e) The distal dural ring and carotid collar (CC) are gently lifted off from the clinoidal segment of internal carotid artery (ICA) and excised until the proximal dural ring that is located at the junction of carotid collar with the dural covering of the cavernous sinus (CS). This helps in exposing the proximal aspect of neck of the aneurysm arising from the internal carotid artery (ICA). II: optic nerve. (f) After excising of the carotid collar (CC), the clinoidal segment of internal carotid artery (ICA) is exposed (arrow)

Figure 4: Case 1: (a) The coring the anterior clinoid process (ACP) from within its bony shell is done using a 3-4mm diamond drill. This is helpful in drilling out the posterior strut of anterior clinoid process (ACP). #: Drilled planum sphenoidale; II: Optic nerve; ICA: Internal carotid artery; CS: Cavernous sinus. (b) The last portion of the posterior root (optic strut) of the anterior clinoid process (ACP) is being drilled, thereby mobilizing the ACP. #: Drilled planum sphenoidale; II: Optic nerve; ICA: Internal carotid artery; CS: Cavernous sinus. (c) The mobilized shell of anterior clinoid process (ACP) is gently dissected off from the carotid collar (CC), the fascial layer covering the clinoidal segment of internal carotid artery. #: Drilled planum sphenoidale; II: Optic nerve; ICA: Internal carotid artery; CS: Cavernous sinus. D: Removal of the anterior clinoid process by drilling its anterior strut (the portion between the planum sphenoidale (#) and anterior clinoid process; and, also its posterior strut (the core of the anterior clinoid process) exposes the distal dural ring (DDR), the proximal dural ring and the carotid collar [CC; the fascia covering the proximal clinoidal segment of the internal carotid artery (ICA)], as the internal carotid artery (ICA) curves laterally to enter the cavernous sinus (CS). The junction of distal cavernous sinus dura and the thickened proximal aspect of the carotid collar forms the proximal dural ring. The drilling of the planum sphenoidale (#) over the roof of optic foramen has exposed the distal part of optic nerve (II). The latter may gently be mobilized medially to access the proximal aspect of neck of the aneurysm. (e) The distal dural ring and carotid collar (CC) are gently lifted off from the clinoidal segment of internal carotid artery (ICA) and excised until the proximal dural ring that is located at the junction of carotid collar with the dural covering of the cavernous sinus (CS). This helps in exposing the proximal aspect of neck of the aneurysm arising from the internal carotid artery (ICA). II: optic nerve. (f) After excising of the carotid collar (CC), the clinoidal segment of internal carotid artery (ICA) is exposed (arrow)