Elena Zapata-Arriaza, MD

Lin MP, Brott TG, Liebeskind DS, Meschia JF, Sam K, Gottesman RF. Collateral Recruitment Is Impaired by Cerebral Small Vessel Disease. Stroke. 2020;51:1404–1410.

Small vessel disease (SVD) is clearly related to increased stroke risk and worse functional outcome. However, the effect of mentioned SVD on the vasodilatory capacity of arteriole and microvasculature for collaterals recruitment during an acute stroke scenario is unclear. Lin and colleagues performed a study to asses SVD effect on collaterals development in acute stroke setting.

For this study, consecutive patients with middle cerebral artery or internal carotid artery occlusion presenting within 6 hours after stroke symptom onset who underwent thrombectomy from 2012 to 2017 were included. The primary outcome was poor collateral flow (assessed on baseline computed tomographic angiography). Markers of chronic SVD on brain magnetic resonance imaging were rated for the extent of white matter hyperintensities, enlarged perivascular spaces, chronic lacunar infarctions and cerebral microbleeds using the Standards for Reporting Vascular Changes on Neuroimaging criteria. Severity of SVD was quantified by adding the presence of each SVD feature, with a total possible score of 0 to 4; each SVD type was also evaluated separately.

After data analysis, the authors included 100 patients, with 68% of any SVD. Poor collaterals were observed in 46%, and those with SVD were more likely to have poor collaterals than patients without SVD. Of the SVD types, poor collaterals were significantly associated with white matter hyperintensities (aOR, 2.9 per Fazekas increment [95% CI, 1.6–5.3]) but not with the other SVD markers analyzed. Having a greater number of different SVD markers was associated with higher odds of poor collaterals. There was a dose-dependent relationship between white matter hyperintensity burden and poor collaterals: adjusted odds of poor collaterals were 1.5, 3.0, and 9.7 across Fazekas scores of 1 to 3. No patient with an SVD score of 4 had good collaterals.

The SVD-poor collateral correlation found in the present study offers relevant hypotheses that should be confirmed in larger studies. At the moment, it is unlikely that those patients with SVD who are candidates for thrombectomy will be ruled out for endovascular treatment. Impact of SVD on collaterals in acute stroke, could be the key in futile recanalization. SVD and poor collaterals could be understood as synonyms; but with  a dose-dependent relationship between WMH and poor collaterals. Thus, a mild SVD may have more difficulties in recruiting collaterals compared to a healthy patient, but even so, it is very likely that if rapid recanalization is achieved, patients could benefit from endovascular treatment.

It would be interesting to validate these results using non-contrast brain CT, the most widespread imaging test in daily clinical practice. Collaterals give us time to perform mechanical thrombectomy, and given this scientific work results, it is possible that patients with SVD have had an hourglass against them since the start of the large vessel occlusion, which should push us to act more quickly in these cases.