To study the co-existence of small-vessel vasculopathy in subordinate branches emanating from high-grade intracranial large-artery atherosclerosis

Patients with acute ischemic stroke attributed to high-grade (60-99%) middle cerebral artery (MCA) or basilar artery (BA) stenosis underwent 3-dimensional rotational angiography (3DRA) to delineate the patency of subordinate branches emanating immediately from the stenotic segments. For MCA stenoses, we scrutinised lenticulostriate artery, anterior temporal artery, and occasionally, an early M2 branch from a horizontal M1 segment. For BA lesions, we examined superior cerebellar artery and anterior inferior cerebellar artery.

We diagnosed branch atheromatous disease (BAD) if an ostial atheroma occluded >50% the orifice of a subordinate branch/perforator. BAD could be ‘adjoining BAD’ if the junctional atheroma was contiguous and morphologically inseparable from the main bulk of the parent plaque; or ‘isolated BAD’ if the orifical atheroma was discrete from the parent plaques.

We diagnosed intrinsic small-vessel vasculopathy if the steno-occlusion was distinctively distal to a normal orifice.

Among the 146 patients harbouring MCA (n=132) or BA plaques (n=14), the median luminal stenosis was 75%. 101 patients (69%) had steno-occlusions further in the penetrating arteries/subordinate branches within these high-grade ICAD segments. By anatomic location, these small-vessel steno-occlusions (n=107) were primarily orifical (due to adjoining BAD (n=88) or isolated ostial atheroma (n=6)). Distal intrinsic vasculopathy was much less common (n=13).