An update to the Raymond-Roy Occlusion Classification of intracranial aneurysms treated with coil embolization

Background The Raymond-Roy Occlusion Classification (RROC) is the standard for evaluating coiled aneurysms (Class I: complete obliteration; Class II: residual neck; Class III: residual aneurysm), but not all Class III aneurysms behave the same over time. Methods is a retrospective review of 370 patients with 390 intracranial aneurysms treated with coil embolization. A Modified Raymond-Roy Classification (MRRC), in which Class II la designates contrast within the coil interstices and Class IIIb contrast along the aneurysm wall, was applied retrospectively. Results Class II la aneurysms were more likely to improve to Class I or II than Class IIIb aneurysms (83.34% vs 14.89%, p<0.001) and were also more likely than Class II to improve to Class I(52.78% vs 16.90%, p<0.001). Class II lb aneurysms were more likely to remain incompletely occluded than Class II la aneurysms (85.11% vs 16.67%, p<0.001). Class II lb aneurysms were larger with wider necks while Class II la aneurysms had higher packing density. Class II lb aneurysms had a higher retreatment rate (33.87% vs 6.54%, p<0.001) and a trend toward higher subsequent rupture rate (3.23% vs 0.00%, p=0.068). Conclusions We propose the MRRC to further differentiate Class III aneurysms into those likely to progress to complete occlusion and those likely to remain incompletely occluded or to worsen. The MRRC has the potential to expand the definition of adequate coil embolization, possibly decrease procedural risk, and help endovascular neurosurgeons predict which patients need closer angiographic follow-up. These findings need to be validated in a prospective study with independent blinded angiographic grading.