Vertebrobasilar, non-sacular and dolichoectatic aneurysms (VBDAs) often represent a therapeutic challenge to clinicians – observe, serial image, or treat? The current study by Nasr et al adds further support to the pre-existing literature that VBDAs are generally associated with a poor natural history with high growth and rupture rates.
The authors performed a retrospective study on all VBDAs seen at their hospital. VBDAs were defined to include fusiform aneurysms (aneurysms with focal dilitations without a definable neck), dolichoectasia (uniform aneurysm dilitations), and transitional aneurysms (uniform aneurysm dilitations with superimposed dilitations of a focal portion of the involved artery). Dissecting aneuryms were excluded as the authors felt these lesions have a distinct natural history.
152 patients with VBDAs were followed for a mean of 3.6 years. 30% of the aneurysms were fusiform, 49% were dolichoectatic, and 21% were transitional. The median diameter of the aneurysms was 7.2mm. 23% of aneurysms demonstrated growth (>2mm) during the course of the study, resulting in an annual aneurysm growth rate of 6.5%. 5.3% (8) of aneurysms ruptured during follow-up, yielding a rupture rate of 1.5%/year and 13.2% of patient with VBDAs had posterior circulation infarcts.
In univariate analyses, aneurysm type, large (>10mm) aneurysms, presence of T1 signal in the aneurysm rim (representing subacute thrombus), presence of thrombus, and presence of daughter aneurysm were also associated with aneurysm rupture. However, in multivariate analyses, only aneurysm type was associated with aneurysm growth and rupture: transitional aneurysms had significantly higher odds of growth/rupture than dolichoectatic, but not fusiform aneurysms
The main limitations include the lack of standardization of imaging modality and lack of pre-specified time of imaging follow-up.
Overall, this study confirms that VBRAs, and in particular transitional vertebrobasilar aneurysms, have high rates of growth and rupture and warrant close imaging follow-up. Further research will be needed to better distinguish which aneurysms are at highest risk for rupture and may potentially benefit from treatment.