Abstract Body: Introduction: Literature demonstrates that nearly one-third of acute ischemic stroke (AIS) patients with large vessel occlusion (LVO) or severe stenosis arrive at the emergency room with mild symptoms, attributed to favourable collateral status. However, approximately 20~40% of patients with mild symptoms due to LVO or severe stenosis are at risk of early neurological deterioration (END) as a consequence of subsequent collateral failure post arrival. This study aimed to identify the difference of collateral patterns between mild stroke patients with END and those without.
Methods: AIS patients presenting within 24 hours from last known well, with a baseline NIHSS≤5 and anterior circulation LVO or severe stenosis were included. Patients who underwent endovascular treatment before END were excluded. END was defined as an increase in total NIHSS≥4 or NIHSS≥2 for any item within 72 hours, without evidence of parenchymal hemorrhage. Collateral flow was rated as the Tan scale (leptomeningeal collaterals) and cerebral blood volume (CBV) index (cerebral blood flow reserve). A good leptomeningeal collateral score (goodCS) was defined as Tan scale≥2 (poorCS: Tan scale <2). CBVindex was calculated as the ratio of mean CBV within Tmax>6s lesion over the mean CBV of Tmax<4s area.
Results: A total of 237 AIS patients with mild symptoms due to anterior circulation LVO or severe stenosis were included and END occurred in 22% of the patients. Stepwise logistic regression analysis revealed that higher CBVindex and poorCS were associated with the increased risk of END occurrence. The optimal threshold of CBVindex predicting END was 0.735 (sensitivity: 0.83; specificity:0.48). Accordingly, patients were divided into four groups: group1: CBVindex<0.735+ poorCS; group2: CBVindex<0.735+goodCS; group3: CBVindex>0.735+goodCS; group4: CBVindex>0.735+ poorCS. Further analysis showed that that patients with CBVindex>0.735 and poorCS (group 4) were most likely to present with END (logistic OR[95%CI]: 5.18[1.22,22.18] P=0.026).
Conclusions: Higher CBVindex and poor leptomeningeal collaterals were independent predictors of END in patients with mild symptoms due to anterior circulation LVO or severe stenosis. Therefore, we hypothesize that though higher CBVindex reflects favorable collaterals at baseline, higher CBVindex combined with the absence of goodCS indicates insufficient blood flow reserve, leading to collapse of collateral flow during acute phase, therefore, the occurrence of END.