The role of impaired autoregulation in cerebral small vessel disease and vascular cognitive impairment

Cerebral autoregulation is the fundamental mechanism that regulates cerebral blood flow in the face of blood pressure variability. It is a dynamic process that depends on vascular smooth muscle cell contractile function, driven by myogenic, chemical and autonomic mechanisms. Cerebral small vessel disease (cSVD) is associated with increased blood pressure variation due systemic haemodynamic dysfunction, as well as dysfunction of the cerebral small vessels, characterised by endothelial dysfunction and vascular reactivity. As such, cerebral autoregulation may be impaired in cSVD, either as a manifestation of the disease or as a cause. This narrative review addresses current clinical evidence for involvement of autoregulatory dysfunction in cSVD. It discusses the mechanisms of autoregulation; how these overlap with vascular mechanisms involved in cSVD; methods of measurement of autoregulation these patients; evidence for altered autoregulation in patients with either sporadic cSVD, previous stroke or specific forms of cSVD; and effects of potential therapies for cSVD on autoregulation. This review thereby identifies the potential importance of autoregulation in cSVD, highlights current limitations in our understanding, and outlines future research avenues.