Distinct Perforator Hemodynamic Phenotypes Differentiate Mechanisms of Single Subcortical Infarction: In Vivo Evidence from 7T Phase-Contrast MRI

ObjectiveSingle subcortical infarction (SSI) arises from heterogeneous mechanisms, most commonly parent artery disease (PAD) or intrinsic small vessel pathology. However, whether these mechanisms produce distinct in vivo hemodynamic signatures within perforating arteries remains unknown. We aimed to determine whether lenticulostriate artery (LSA) hemodynamics differ between SSI subtypes and whether such differences provide mechanistic insight into SSI pathophysiology.MethodsPatients with recent SSI confined to the LSA territory were prospectively enrolled and underwent 7T MRI. Based on intracranial vessel wall imaging, patients were classified as SSI+PAD (ipsilateral MCA plaque on T1-weighted vessel wall imaging defined by eccentric wall thickening)) or SSI-PAD (no ipsilateral MCA plaque). LSA flow velocity was quantified at the arterial ostium and distal segment using phase-contrast magnetic resonance angiography (PC-MRA), and along-vessel velocity decline was calculated. LSA morphology was assessed with time-of-flight MRA. Linear mixed-effects models adjusted for age and sex were used for group comparisons.ResultsForty-two patients (21 SSI+PAD and 21 SSI-PAD) were included. In SSI+PAD, ostial velocity in the symptomatic hemisphere was significantly lower than in the contralateral hemisphere (7.25 vs. 9.61 cm/s; p<0.001) and the symptomatic side of SSI-PAD (8.95 cm/s, p=0.001), indicating proximal inflow restriction. In contrast, SSI-PAD preserved ostial inflow (8.95 vs. 9.15 cm/s, p = 0.70) but exhibited a greater along-vessel velocity decline on both hemispheres compared with SSI+PAD, suggesting distal microvascular dysfunction. Morphologically, the symptomatic hemisphere showed fewer visible LSA branches and shorter LSA length than the contralateral hemisphere in both groups. In addition, LSA diameter tended to be smaller in SSI-PAD than in SSI+PAD.Conclusion7T PC-MRA revealed distinct hemodynamic patterns in SSI. SSI+PAD was characterized by proximal inflow limitation, whereas SSI-PAD reflected diffuse distal hypoperfusion characteristic of small vessel pathology. Quantitative perforator flow assessment may refine etiologic classification and guide second prevention in SSI.