Vertebrobasilar Stroke: Association Between Infarction Patterns and Quantitative Magnetic Resonance Angiography Flow State

Background Treatment and prognosis of vertebrobasilar atherosclerotic disease differs depending on stroke mechanism, such as artery-to-artery embolism, branch atheromatous disease, and hemodynamic ischemia. Our aim was to investigate the relationship between infarction pattern and flow status using quantitative magnetic resonance angiography (QMRA), to determine the validity of using infarction patterns to infer stroke mechanism. Methods and Results This is a retrospective study of patients with ischemic stroke with intra- or extracranial vertebrobasilar atherosclerotic stenosis, who underwent magnetic resonance imaging of the brain, neurovascular imaging, and QMRA, between 2009 and 2021. Patients with cerebral infarction predating or following QMRA by >= 1 year, or QMRA studies performed for basilar thrombosis, vertebral dissection, or only postangioplasty/stenting, were excluded. Poststenotic flow (basilar and posterior cerebral arteries) was dichotomized as low-flow or normal-flow based on published criteria. Of 1211 consecutive patients who underwent QMRA noninvasive optimal analysis, 69 met inclusion. Mixed patterns were most common (46.4%), followed by perforator (23.2%), borderzone (14.5%), and territorial (15.9%). Patients with low-flow had a significantly higher rate of borderzone+ patterns (borderzone alone or in mixed pattern) compared with patients with normal-flow (77.4% low-flow versus 39.5% normal-flow, P=0.002). Borderzone+ patterns were associated with 61.5% probability of low-flow state, while no borderzone (perforator/territorial) patterns were associated with 76.7% probability of normal-flow state. Conclusions Borderzone infarction pattern (alone or mixed) was associated with low poststenotic posterior circulation flow by QMRA. However, borderzone pattern only moderately predicted low-flow state, and may be an unreliable flow marker. Therefore, infarct topography may complement, but should not replace hemodynamic studies to establish flow status.