Raymond–Roy occlusion classification of intracranial aneurysms
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The Raymond–Roy occlusion classification (RROC) is an angiographic classification scheme for grading the occlusion of endovascularly treated intracranial aneurysms 1. It is also known as the Raymond class, Montreal scale or the Raymond Montreal scale.
class I: complete obliteration
class II: residual neck
class III: residual aneurysm
The scheme was originally created to evaluate aneurysm occlusion class, and not predict aneurysmal recurrence. Though not truly equivalent these are often equated to aneurysmal obliteration of 100%, >90% and <90% respectively.
Modified Raymond–Roy classification
Mascitelli et al. 1 in 2015 proposed a modified Raymond–Roy classification (MRRC) or modified Montreal scale, where class III is subdivided to reflect progression to occlusion:
class IIIa: contrast opacification within the coil interstices of a residual aneurysm
class IIIb: contrast opacification outside the coil interstices, along the residual aneurysm wall
The study from Mascitelli et al. found that class IIIa aneurysms progress to complete occlusion more than class IIIb aneurysms.
A validation study by Stapleton et al. confirmed that the predictive capability of the RROC was improved by the MRRC, showing not only that IIIa occluded more often (53.6% vs 19.2%) but that IIIb lesions would also further recanalize more frequently (65.1% vs 27.4%) 2.