The role of the autonomic nervous system in cerebral blood flow regulation in stroke: A review.

Stroke is a pathophysiological condition which results in alterations in cerebral blood flow (CBF). The mechanism by which the brain maintains adequate CBF in presence of fluctuating cerebral perfusion pressure (CPP) is known as cerebral autoregulation (CA). Disturbances in CA may be influenced by a number of physiological pathways including the autonomic nervous system (ANS). The cerebrovascular system is innervated by adrenergic and cholinergic nerve fibers. The role of the ANS in regulating CBF is widely disputed owing to several factors including the complexity of the ANS and cerebrovascular interactions, limitations to measurements, variation in methods to assess the ANS in relation to CBF as well as experimental approaches that can or cannot provide insight into the sympathetic control of CBF. CA is known to be impaired in stroke however the number of studies investigating the mechanisms by which this occurs are limited. This literature review will focus on highlighting the assessment of the ANS and CBF via indices derived from the analyses of heart rate variability (HRV), and baroreflex sensitivity (BRS), and providing a summary of both clinical and animal model studies investigating the role of the ANS in influencing CA in stroke. Understanding the mechanisms by which the ANS influences CBF in stroke patients may provide the foundation for novel therapeutic approaches to improve functional outcomes in stroke patients.