A case of mistaken identity: intraoperative discovery of an extracranial internal carotid artery aneurysm.

The optimal diagnostic modality for extracranial carotid artery aneurysm is not firmly established because of the emerging trend of replacing traditional carotid angiography with magnetic resonance imaging and angiography. An extracranial carotid artery aneurysm can have profound neurologic sequelae, and an elective resection is often suggested. Imaging studies should firmly establish the diagnosis and differentiate the aneurysm from other lesions of the carotid, especially carotid body tumor, prior to surgical planning. Magnetic resonance studies may not properly distinguish between different lesions of the carotid arteries. This case of an unexpected carotid aneurysm found intraoperatively demonstrates that while traditional angiography is costly and invasive, it is still the diagnostic study of choice when an aneurysm is a possible diagnosis.