A Classification Scheme for Assessing Recanalization and Collateral Formation following Cerebral Venous Thrombosis

Abstract

There has been substantial emphasis placed on categorizing recanalization and collateral
formation in patients with acute arterial occlusion resulting in ischemic stroke.1-4 Such
methods of semi-quantitatively classifying the severity of arterial occlusion for prognostic
purposes and assessing the response to treatment have become an integral part of clinical
studies.3-4 However, no such method exists for classifying either recanalization or collateral
formation in patients with cerebral venous thrombosis. A method with two components
is described that can be used to classify recanalization and collateral formation in patients
with cerebral venous thrombosis using serial magnetic resonance (MR) or computed
tomographic (CT) venography or catheter based angiography with venous phase imaging.
The recanalization is classified as follows (see Figure): grade I, partial recanalization of one or
more occluded dural sinus with improved collateral flow; grade II, complete recanalization of
one sinus but persistent occlusion of the other sinuses [A-no residual flow, B-non occlusive
flow]; and grade III, complete recanalization. The collateral formation is classified as follows:
grade I, collaterals-bypass occluded segment of dural venous sinus but connect within the same sinus; grade II, collaterals bypass
occluded segment but connect with a different sinus; and grade III, collaterals bypass the occluded segment and connect with different
circulation. The classification recognizes the superficial and deep venous circulation as distinct pathways with different prognostic
implications5
that can be linked through collateral pathways. Further studies are required to assess the inter-observer reliability of
the proposed classification and assess the ease of use in clinical studies and practice. Identification of patterns of recanalization and/
or collateral formation associated with minimal residual d