Our review aimed to evaluate the existing data on the natural history of neck residuals with regards to recanalization rate (Class II worsening to Class III) versus rate of progressive occlusion (Class II to Class I, or obliteration)

The degree of intracranial aneurysm embolization required to prevent subsequent rupturing is not well established. Retreatment of residual portions of the aneurysm (neck and aneurysmal sac) requires a potential benefit that justifies the risk of endovascular intervention. Aneurysmal neck residual are suspected to carry less risk for subsequent regrowth. Due to the variable morphology of neck residuals and the lack of natural history studies, the degree to which neck residuals can be considered a favorable outcome after initial treatment is unknown

The Raymond–Roy Occlusion Classification (RROC) was used in order to define neck residuals in this study. Utilizing PRISMA guidelines, we undertook a systematic literature review for endovascular treatment of ruptured and unruptured intracranial aneurysms resulting in Class II neck residuals, and determined rates of recanalization and progressive occlusion. 22 out of 1105 studies analyzed were selected to characterize the angiographic evolution of neck residuals.

A total of 1002 class II aneurysms were included in the analysis. The average angiographic follow-up after initial treatment was 13.8 ± 9.0 months. Upon angiographic follow-up a total of 150 (14.9%) aneurysms recanalized, 429 (42.8%) evolved to progressive occlusion, and 423 (42.2%) remained stable (no change in classification). Additionally, out of 696 initial treatment class II aneurysms with available data, 156 (22.4%) had stand-alone coiling, 508 (73.0%) underwent stent-assisted coiling, and 32 (4.6%) had balloon-assisted coiling.

There is a greater tendency of neck residual (Class II) aneurysms to remain stable or evolve to progressive occlusion versus worsening to Class III residual status.