Thrombosed aneurysm of the cervical carotid artery: avoiding a retrospective diagnosis.

Two patients with neck masses were evaluated, one with computed tomography (CT) and the other with magnetic resonance (MR) imaging. Each mass was correctly identified within the carotid sheath. The correct diagnosis-thrombosed cervical carotid aneurysm--was not considered, necessitating unexpected repair of the aneurysm or artery. Although rare, aneurysm of the cervical carotid artery should be considered in the differential diagnosis of a carotid sheath mass between the jugular vein and carotid artery. Peripheral calcification or enhancement on CT scans and a peripheral signal void on MR images are especially suggestive of the diagnosis.