Background and purpose Vertebrobasilar fusiform and dolichoectatic aneurysms (VFDAs) are characterized by arterial dilatation, elongation and/or tortuosity. These lesions are houghave a poor natural history with high rates of growth, rupture, compressive symptoms and associated ischemia. We sought to characterize the natural history of VFDAs receiving serial imaging.
Methods Patients with vertebrobasilar fusiform or dolichoectatic aneurysms demonstrated on CT/CTA, MRI/MRA and DSA studies between 2001–2014 were identified. Only patients who had serial imaging were included in this study. VFDAs were categorized into three morphological categories: 1) Fusiform aneurysm-dilatation of only a portion of an arterial segment, 2) Dolichoectatic aneurysm-uniform dilatation of the entire artery segment and 3) Transitional aneurysm-uniform aneurysmal dilatation of an entire arterial segment with superimposed dilatation of a portion of the involved arterial segment.
Initial and serial imaging studies were reviewed by an interventional neuroradiologist, neurologist and diagnostic radiologist. We defined VFDA enlargement as an increase of ≥2 mm. Additional outcomes included imaging evidence of posterior circulation infarction, VFDA rupture and mass effect. We performed a subgroup analysis of growth and rupture rates of VFDAs ≥10 mm in maximum diameter. Continuous variables were compared with Student’s T-tests and categorical variables were compared using chi-squared tests.
Results A total of 139 VFDA patients were included in this study (38 fusiform, 74 dolichoectatic and 27 transitional). Mean patient age was 59 ± 13 years. 104 patients (74.8%) were male. Mean follow-up was 42 months. Mean VFDA baseline diameter was 8.6 ± 4.7 mm. 29 VFDAs grew (20.8%) ≥2 mm for an annual growth rate of 5.9% per year. Five VFDAs ruptured (3.6%) for an annual rupture rate of 1.0% per year. Eighteen patients (12.9%) had increased radiological mass effect on follow-up. 19 patients (13.7%) had a new posterior circulation infarct on follow-up. In our subgroup analysis of aneurysms with baseline diameter≥10 mm, 16 of 26 aneurysms grew during the follow-up period (61.5%) for a growth rate of 30.8% per year. 2 aneurysms ruptured (7.7%, 2/26) for a rupture rate of 3.8% per year. Baseline variables associated with growth and/or rupture included presence of mass effect (P = 0.02), high T1 signal in the aneurysm rim (P = 0.006), presence of a daughter sac (P = 0.003), thrombus formation (P = 0.0001) and increasing diameter.
Conclusions Vertebrobasilar fusiform and dolichoectatic aneurysms, especially those 10 mm or larger, are associated with a poor natural history with high growth and rupture rates. Further research is needed to determine the best treatments for this disease in high risk patients.
Disclosures D. Nasr: None. A. Rouchaud: None. W. Brinjikji: None. D. Kallmes: None. K. Flemming: None.