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Neuroradiology

E2809. More Than a Bump in the Road: Imaging Characteristics and Treatment of Blisterlike Aneurysms

Danda D,  Rao B. Yale New Haven Hospital, New Haven, CT

Address correspondence to D. Danda (dipandanda@yahoo.com)

Background Information: A blisterlike aneurysm (BLA) is a small, broad-based, shallow outpouching that classically occurs in the dorsal wall of the supraclinoid internal carotid artery (ICA) and accounts for 0.3–7.8% of ruptured intracranial aneurysms. Compared with the more common saccular aneurysms, BLAs are not known to occur at the branch points of the cerebral arteries and present in younger patients with a reported mean age ranging between 41.8–53.7 years with a suggestion of a female predominance. Diagnostically, the identification of BLAs are challenging due to their atypical morphology and location particularly when they are found in nonclassic locations. BLAs also present therapeutic challenges. The diagnosis of a BLA portends a poor prognosis in comparison to a saccular aneurysm because of higher rates of intraoperative rupture, morbidity, and mortality, which are further increased in cases of more severe subarachnoid hemorrhage (SAH) as determined by the Hunt & Hess or Fisher scales. Furthermore, the rates of intraoperative rupture and mortality have been found to be increased in cases without a preoperative diagnosis of a BLA.

Educational Goals/Teaching Points: The purpose of this exhibit is to review the appearance of the blister-like aneurysms on CT, MRI, and angiography and to review treatment and associated complications.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: BLAs classically occur in the dorsal wall of the supraclinoid ICA. Common nonclassic locations for BLAs are the anterior communicating artery and the middle cerebral artery. CT angiography (CTA) is not sensitive enough to replace digital subtraction angiography which remains the reference standard for the detection of BLAs. Time-of-flight MR angiography is the most widely accepted technique for the detection of BLAs. Emerging MRI techniques such as vessel wall imaging can help identify ruptured aneurysms by demonstrating thick enhancement of aneurysm wall or intramural hematoma. Endovascular treatments such as the use of flow-diverting stents is associated with lower rates of morbidity and mortality in those with less severe SAHs. Surgery is associated with better outcomes in those with more severe SAHs.

Conclusion: Identification and appropriate management are essential to decrease the morbidity and mortality portended by diagnosis of a BLA