Magnetic resonance imaging for assessment of cerebrovascular reactivity in cerebral small vessel disease: A systematic review.

Cerebral small vessel disease (SVD) pathophysiology is poorly understood. Cerebrovascular reactivity (CVR) impairment may play a role, but evidence to date is mainly indirect. Magnetic resonance imaging (MRI) allows investigation of CVR directly in the tissues affected by SVD. We systematically reviewed the use of MRI to measure CVR in subjects with SVD. Five studies (total n = 155 SVD subjects, 84 controls) provided relevant data. The studies included different types of patients. Each study used blood oxygen level dependent (BOLD) MRI to assess CVR but a different vasoactive stimulus and method of calculating CVR. CVR decreased with increasing white matter hyperintensities in two studies (n = 17, 11%) and in the presence of microbleeds in another. Three studies (n = 138, 89%) found no association of CVR with white matter hyperintensities. No studies provided tissue-specific CVR values. CVR decreased with age in three studies, and with female gender and increasing diastolic blood pressure in one study. Safety and tolerability data were limited. Larger studies using CVR appear to be feasible and are needed, preferably with more standardized methods, to determine if specific clinical or radiological features of SVD are more or less associated with impaired CVR.