Dural waisting as a sign of subarachnoid extension of cavernous carotid aneurysms: a follow-up case report.

OBJECTIVE: Even when augmented by CT and MRI, it can be difficult on angiography to predict which intracavernous carotid artery aneurysms (ICCAA) have subarachnoid extension and therefore pose a higher risk of subarachnoid hemorrhage. Previously we reported a case of an ICCAA, which on angiogram had a focal tapering of the dome that we termed a "waist." At surgery this lesion was found to have subarachnoid extension. We postulated that this dural "waisting" on the arteriogram was a predictor of subarachnoid extension. Herein we report a second case of an ICCAA with the angiographic appearance of a waist that was also confirmed to have subarachnoid extension at surgery, thereby strengthening our original hypothesis.

CLINICAL PRESENTATION: A 40-year-old woman presented with a 3-month history of bitemporal headache, diplopia, and a left sixth nerve palsy. MRI showed a lesion in the vicinity of the left cavernous carotid sinus and an arteriogram confirmed the presence of a large cavernous carotid aneurysm. As in the previous case, the aneurysm fundus was indented, creating a waist on the aneurysm dome.

INTERVENTION: After passing a trial balloon occlusion of the involved carotid artery, the patient was brought to the operating room for lesion trapping. The aneurysm fundus was seen to extend beyond the falciform ligament and with subsequent dissection, the neck of the aneurysm was seen to incorporate the carotid artery distal to the ophthalmic artery. The aneurysm was trapped by ligating the internal carotid artery in the neck and by placing a clip on the intracranial carotid proximal to the posterior communicating artery.

CONCLUSION: The presence of subarachnoid extension of an ICCAA can be difficult to elucidate on an arteriogram. This is an additional case in which a focal narrowing or "waisting" of the aneurysm dome seen on an angiogram served as a marker of subarachnoid extension.