Images in Vascular Medicine: A rare case of intimomedial mucoid degeneration of the carotid artery

A 30-year-old White man was admitted with a sudden onset of right faciobrachial weakness. A brain computed tomography (CT) scan revealed no acute cerebral ischemic, hemorrhagic lesions or large vessel occlusions. Computed tomography angiography (CTA) showed a 13 × 14 mm diameter saccular aneurysm in the right extracranial internal carotid artery (ICA) with concomitant carotid kinking and two other small aneurysms (2 mm in diameter) in the left ICA (Panels A1 and A2, arrows).

The patient underwent intravenous thrombolysis with early regression of neurological symptoms.

An angiography confirmed the presence of carotid aneurysms (Panels B1 and B2, arrows) and the absence of arteriovenous malformations or cerebral vasospasm.

After multidisciplinary discussion, we performed an elective right aneurysmectomy. The location of the aneurysm allowed clamping of the ICA only, allowing blood flow from the external carotid artery through the collateral vessels to be maintained. After resecting the aneurysm, a direct end-to-end anastomosis was performed on the ICA, restoring direct flow, without the need for prosthetic graft material, and correcting the kinking (Panel C). Surgical excision was considered by us to be the best choice because in suspected connective tissue pathology it allowed a pathologic diagnosis to be established. Histopathologic evaluation of the resected aneurysm revealed mucoid deposition of the intima and the media (Panels D1 to D3). The postoperative course was uneventful, and a duplex ultrasound examination after 3 months showed patency of the carotid artery and absence of pseudoaneurysm or anastomotic stenosis.

For the two small left carotid aneurysms, we opted for conservative management with antiplatelet therapy and watchful waiting. The patient also underwent a total body CT scan, which revealed no other aneurysms as well as stability of left carotid aneurysms.

Intimomedial mucoid degeneration (IMD) is a rare vascular disorder of unknown etiology characterized by mucinous deposits in the intima and media that cause elastic fiber degeneration, resulting in aneurysmal degeneration of the vessel wall. ¹ IMD typically occurs in young patients, ² with a strong predominance of Black South African female patients. ³ Although the abdominal aorta is the most commonly involved artery, more recent reports have described the involvement of the major aortic branches (subclavian, carotid, superior mesenteric, iliac, femoral arteries) ² and smaller vessels including coronary, ⁴ brachial, ⁵ dorsalis pedis, ³ and temporal arteries. ⁶

Only two cases of carotid artery aneurysm in patients with IMD have been described in the literature so far. ⁷ Ours is the third case of carotid artery aneurysm caused by intimomedial mucoid degeneration reported in the literature.

IMD is a histopathologic entity distinct from cystic medial necrosis, which has an important role in the development of arterial aneurysms in certain patients. Although IMD is a rare condition, it is important to consider this vascular disorder as an uncommon case of aneurysm in the younger population. The young age of these patients imposes the need for long-term surveillance and follow-up, together with CT, for the detection of any new aneurysmal formation.

Panel A.

Panel B.

Panel C.

Panel D.