Cerebral vascular diameter and flow irregularities due to ischemic stroke after middle cerebral artery occlusion

Acute ischemic stroke is a major cause of death and disability. Although reperfusion therapies are effective, early and lasting alterations in the microvasculature can limit recovery. Research has largely focused on microvascular impairment, whereas the pial arterial network remains relatively underexplored. Using the middle cerebral artery occlusion model and in vivo microscopy in mice, we assessed pial vessel dynamics during occlusion, recanalization, and the first 24 h of reperfusion. We analyzed vessel diameter, irregularity, resistance, blood flow, and microthrombus formation. Results revealed marked vasoconstriction throughout the pial network during occlusion, which persisted after recanalization, with vessel diameters reduced to 72 ± 27% (SD) of baseline at 24 h. Smaller pial vessels (<30 µm) reacted differently over time compared with larger vessels. Vessel irregularity and resistance increased and peaked at 24 h. A considerable proportion of vessels had impaired flow and microthrombi at all time points. Thrombosis risk in daughter vessels rose when a mother vessel contained a thrombus. In conclusion, recanalization is insufficient to avert early and persistent vascular dysfunction in this model. Our findings underscore the role of pial artery impairment in disturbed reperfusion and point to the need for complementary strategies to restore adequate blood flow and improve outcomes.NEW & NOTEWORTHY This study investigated vasoconstriction in the larger pial arteries, a network relatively underexplored in vascular stroke research, during and after ischemic stroke. By measuring vessel diameters along the entire vessel length, we uncovered effects of local constriction on vessel irregularity and resistance not reported before in vascular literature. By imaging during occlusion and hyperacutely after reperfusion, this study investigated thrombi formation and flow impairments at critical time points, providing insight lacking in prior research.