Impaired occipital cerebrovascular reactivity as a biomarker for vascular β-amyloid

Impaired cerebrovascular reactivity (CVR) represents a decrease in vasodilatory capacity because of arterial wall stiffening and elasticity loss. This measure seems to be a sufficient indication of the adequacy of tissue-level cerebral blood flow in patients with cerebral small vessel disease (CSVD).(1)Decreased CVR, linked to blood-brain barrier dysfunction and reduced microvascular pulsatility, contributes to disturbances in overall perivascular flow and interstitial fluid drainage that, in turn, impede the clearance of metabolites, including beta-amyloid (A beta), from brain tissue. Experimental studies have thus considered impaired CVR a hallmark feature of cerebral amyloid angiopathy (CAA).(2)It remains unclear, however, whether CVR also declines in Alzheimer disease (AD) and, if so, whether it relates to parenchymal A beta deposition or to concomitant CAA.