Capillary stalling: A common microvascular pathway to stroke susceptibility and poor recovery

Capillary stalling, the transient interruption of blood flow within individual capillaries, is a potential indicator of cerebral microvascular dysfunction and may contribute to stroke susceptibility and recovery. Stroke remains a leading cause of death and disability worldwide, yet many patients do not qualify for available interventions, underscoring the need for improved prevention and early detection. Although stroke is traditionally viewed as a disorder of large-vessels, microvascular dysfunction may strongly influence both the likelihood and consequences of cerebrovascular injury. Because capillaries have extremely narrow lumens and low flow velocities, they are particularly vulnerable to obstruction by leukocytes, rigid or aggregated erythrocytes, platelet aggregates, or fibrin-rich microthrombi. Many pathological states increase the frequency and persistence of capillary stalls, with consequences beyond transient perfusion deficits. Capillaries that repeatedly fail to regain flow may be eliminated through pruning without compensatory regrowth, leading to capillary rarefaction, reduced cerebral reserve, and increased ischemic vulnerability. Thus, capillary stalling may actively contribute to progressive deterioration of the cerebral microvascular network. Conditions that increase stroke risk converge on mechanisms that promote capillary stalling, including endothelial activation, leukocyte adhesion, inflammation, altered erythrocyte rheology, and microthrombus formation. These processes occur across diverse disorders including TBI, AD, diabetes, infection, and cerebral small vessel disease, suggesting that capillary stalling is a shared microvascular pathway linking systemic disease to cerebrovascular injury. Persistent stalling may also worsen stroke outcomes by contributing to the no-reflow despite arterial recanalization. Detecting capillary stalling and defining its molecular regulators may reveal new opportunities for stroke prevention and early intervention.