Twenty-eight years later: A case of superior vena cava aneurysm secondary to cystic hygroma

A 34-year-old obese female with a history of left neck cystic hygroma (post-resection and facial reconstruction at age 6 years) was referred for evaluation of asymmetric mediastinal widening on chest X-ray obtained during bariatric surgery evaluation (Panel A, arrows). No prior chest imaging was available. Subsequent chest computed tomography (CT) showed a fusiform aneurysm of the superior vena cava (SVC) (5.3 × 3.4 cm on double oblique measurement; Panel B) and innominate vein, with adjacent curvilinear vascular structures within the surrounding fat, consistent with lymphatic or venolymphatic malformations. The patient was completely asymptomatic, without evidence of SVC obstruction on physical examination. Vascular surgery was consulted and recommended imaging surveillance without initiation of therapeutic anticoagulation, as the aneurysm was felt to likely be congenital and would not warrant intervention if it remained stable on serial evaluations.

Panel A. Panel B.

SVC aneurysms are very rare, usually asymptomatic, and are typically incidentally diagnosed during chest radiography. ¹ The majority of these aneurysms are fusiform as opposed to saccular. In a previous case series of 15 patients with mediastinal cystic hygroma, eight patients also had venous aneurysms, with the majority being SVC aneurysms. ² Therefore, screening may be prudent in this population. Although the underlying pathophysiology remains poorly defined, the association between cystic hygroma and SVC aneurysms may relate to embryonic development, as lymphatic structures have a venous origin, with subsequent development driven by centrifugal growth and sprouting. ³ Given the rarity of these aneurysms, there is no evidence-based approach to management. Generally, asymptomatic fusiform aneurysms without thrombus are just monitored over time. There is no evidence to support the use of anticoagulants in otherwise asymptomatic non-thrombosed SVC aneurysms. Surgical intervention and anticoagulation are warranted when thrombosis is present (which increases the risk for pulmonary embolism), thromboembolism has occurred, or when the aneurysm becomes symptomatic secondary to compression. Open surgical repair includes using a graft in a similar fashion to abdominal aortic aneurysm repair. Stent grafts are rarely used because of the lack of an appropriate landing zone in the superior vena cava.

‘Images in vascular medicine’ is a regular feature of Vascular Medicine. Readers may submit original, unpublished images related to clinical vascular medicine. Submissions may be sent to: Heather L Gornik, Editor in Chief, Vascular Medicine, via the web-based submission system at http://mc.manuscriptcentral.com/vascular-medicine