Cerebral vasomotor reactivity of bilateral severe carotid stenosis: is stroke unavoidable?

Abstract

We evaluated the cerebral hemodynamic features of severe bilateral carotid stenosis by assessing and comparing cerebral vasomotor reactivity (VMR) in the middle cerebral (MCA) and vertebral arteries (VA) by transcranial Doppler and the Diamox (1 g acetazolamide i.v.) test. VMR was evaluated by recording the percentage differences in peak systolic blood flow velocity in each MCA and VA at baseline and by the Diamox test. Twenty-eight symptomatic (SCAS) and 31 asymptomatic (ACAS) patients with bilateral severe (>70%) internal carotid artery stenosis were studied. The mean MCA VMR% was 29 +/- 26.9% in SCAS and 43.2 +/- 26.8% in ACAS patients (P < 0.01). Their respective mean VA VMR% was 30.2 +/- 36.5% and 39.6 +/- 24.4% (P = NS). VMR% of the symptomatic MCA side in SCAS patients was significantly lower than the opposite side (20.5 +/- 31.1% and 39.2 +/- 37.9% respectively; P < 0.03). In contrast, the VA VMR% of both sides in SCAS patients remained similar (28.1 +/- 39.3% and 34.6 +/- 47.9% respectively; P = NS). VMR% of the MCA and VA in ACAS patients was also similar for both sides of bilateral carotid stenosis. The cerebral hemodynamic features differ between SCAS and ACAS patients with bilateral carotid occlusive disease in the anterior part of the circle of Willis. An independent cerebral vascular reserve capacity of the posterior circulation is proposed.

Hemispheric Asymmetry of Visual Cortical Response by Means of Functional Transcranial Doppler

“…According to our results, a degree of ICA stenosis does not influence the MBFV in ipsilateral nor in contralateral PCA, showing that visual evoked response of the PCA remains similar both on the stenosed and the unstenosed side of ICAs in the case of more pronounced metabolic demands of the region and that the degree of ICA stenosis has no impact, or only exceptionally, on the collateralizing capacity of the PCAs. Those results that are in concordance with the results of the previous studies demonstrate an independent cerebral posterior circulation mechanism that compensates very successfully the anterior circulation insufficiency in severe carotid disease [3–7]. Concerning the correlation of the ICA stenosis, one of the limitations of our study was limited number of patients.…”

“…Results of the studies testing the posterior cerebral circulation using visual stimuli in patients with severe carotid stenosis and consecutively compromised anterior cerebral circulation suggest the existence of an independent cerebral vascular reserve capacity of the posterior part of Willis circle [3–7]. Undoubtedly, collateral variations in circle of Willis have to be taken into consideration since they are highly variable [8].…”

Cerebrovascular reactivity predicts stroke in high-grade carotid artery disease

“…19 This semi-invasive test may also be a risk indicator in carotid artery stenosis. 20,21 Furthermore, CO 2 inhalation and breathholding can induce blood pressure increases and thus overestimate the actual vasomotor reactivity. 22 In the present study, a correction for concomitant blood pressure increases was not possible since most of the studies did not monitor blood pressure during the hypercapnic challenge.…”

The cerebral vasomotor response in varying CO2 concentrations, as evaluated using cine phase contrast MRI: Flow, volume, and cerebrovascular resistance indices

“…1 Cerebral vasomotor reactivity (VMR) is an index with which to evaluate the capability of the cerebral arterioles to respond to extrinsic stimulation by vasodilators, such as acetazolamide 2 or hypercapnic challenge. [3][4][5] Previous studies have identified that impaired VMR is associated with a higher risk of stroke 6,7 and transient ischemic attack. 8,9 Further investigation of VMR is, therefore, clinically important.…”