Collateral vessels in acute stroke

During the acute imaging of ischaemic stroke, the presence or absence of collateral vessels is an important consideration when deciding if the patient wouldwill benefit from endovascular thrombectomy (ECR, endovascular clot retrieval) ¹.

Studies have shown that in acute stroke, both CTA and MRA can assessare accurate modalities in assessing the status of collateral vessels ^2-4. The status of these vessels not surprisingly has an impact oninfluences the evolution of the ischaemic penumbra, the size of the core infarct and affects functional outcomes. The presence of good collateral vessels promoteshas been shown to promote recanalization after acute large vessels occlusion and reduces the risk of hemorrhagic transformation by limiting local perfusion impairment ^{5, 7, 8}. The paucity of good collateral vessels also correlates with a higher risk of treatment complications ⁷.

Overall, the poorer the collateral vessels in a region of ischaemia, the larger the core infarct (DWI lesion size ⁵) and the worse the clinical (functional) outcomes ^3-5. Good leptomeningeal collateral vessels have been shown to correlate with lower baseline ASPECTS ³ and robust collateral vessels have been shown to be an independent predictor of final infarct volume ⁴. 

Patients with poor collateral vessels have been termed fast progressors in whom infarct growth rate is quick compared to patients with strong collaterals (, the slow progressors) who canare able to tolerate ischaemia longer without progressing to infarction ¹.

Collateral scoring systems

Several scoring systems have been described in the literature ¹, based either on a single- or multiphase CT angiogram:

• single-phase CTA collateral scores
• multiphase CTA collateral score