Impaired neurovascular coupling in ischaemic stroke patients with large or small vessel disease

There is limited data of neurovascular coupling on stroke patients, especially on comparison of different etiologies. We aim to test the hypothesis that patients with small vessel disease (SVD) are impaired on neurovascular coupling rather than stroke patient with large intracranial artery stenosis (LIAS), because small vessel is more associated with microcirculatory function. To assess microcirculatory integrity of stroke patients, we performed a functional transcranial Doppler test using a standardized visual stimulation test.

The neurovascular coupling was measured in the asymptomatic occipital cortex in ischaemic stroke patients with LIAS, SVD, and healthy elder controls. Bilateral posterior cerebral arteries were monitored to measure evoked flow velocity during resting and visual stimulation phase. Peak systolic flow velocity responses were recorded, and time course of hemodynamic response was modeled according to a control system analysis with the parameters gain, natural angular frequency, attenuation, and rate time.

Reproduced for both sides, the functionally induced flow velocity changes (gain) were significantly lower in LIAS and SVD compared with controls (P < 0.001). Reductions in both stroke groups were in the same order. Neurovascular coupling in LIAS group did not show difference at the side of vessel stenosis compared with non-stenosis side or at different stenotic degrees.

Interestingly, both LIAS and SVD showed an uncoupling of the blood supply of active neurons. This points to an additional small vessel dysfunction in patients with LIAS.