The Utility of Cerebrovascular Reactivity MRI in Brain Rehabilitation: A Mechanistic Perspective

Abstract

Cerebrovascular control and its integration with other physiological systems play a key role in the effective maintenance of homeostasis in brain functioning. Maintenance, restoration, and promotion of such a balance are one of the paramount goals of brain rehabilitation and intervention programs. Cerebrovascular reactivity (CVR), an index of cerebrovascular reserve, plays an important role in chemo-regulation of cerebral blood flow. Improved vascular reactivity and cerebral blood flow are important factors in brain rehabilitation to facilitate desired cognitive and functional outcomes. It is widely accepted that CVR is impaired in aging, hypertension, and cerebrovascular diseases and possibly in neurodegenerative syndromes. However, a multitude of physiological factors influence CVR, and thus a comprehensive understanding of underlying mechanisms are needed. We are currently underinformed on which rehabilitation method will improve CVR, and how this information can inform on a patient’s prognosis and diagnosis. Implementation of targeted rehabilitation regimes would be the first step to elucidate whether such regimes can modulate CVR and in the process may assist in improving our understanding for the underlying vascular pathophysiology. As such, the high spatial resolution along with whole brain coverage offered by MRI has opened the door to exciting recent developments in CVR MRI. Yet, several challenges currently preclude its potential as an effective diagnostic and prognostic tool in treatment planning and guidance. Understanding these knowledge gaps will ultimately facilitate a deeper understanding for cerebrovascular physiology and its role in brain function and rehabilitation. Based on the lessons learned from our group’s past and ongoing neurorehabilitation studies, we present a systematic review of physiological mechanisms that lead to impaired CVR in aging and disease, and how CVR imaging and its further development in the context of brain rehabilitation can add value to the clinical settings.

Reduced Middle Cerebral Artery Blood Velocity Response during Low-Volume High-Intensity Interval Exercise in Chronic Stroke

“…Some hypothesize that reduced cerebrovascular reactivity with aging and in individuals post-stroke is due to arterial stiffness and poor vasomotor capability. 44 Our study supports this hypothesis by showing an association between MCAv responsiveness during HIIT and arterial stiffness. Prior studies have also shown that statin use may increase cerebrovascular reactivity to carbon dioxide and the MCAv response to moderate-intensity continuous exercise in individuals post-stroke.…”

Cerebral blood flow, cerebrovascular reactivity and their influence on ventilatory sensitivity

“…While CVR is a prominent and common test both clinically and in research, it has varying degrees of predictive value for cerebrovascular risk depending on the population investigated; the literature on CVR in ageing and pathology is rife with between‐study methodological inconsistency making collective interpretation difficult, though CVR certainly seems to be impaired with age and several diseases (Alwatban et al., 2021; Hoiland et al., 2019; Krishnamurthy et al., 2021; Lu et al., 2011; Williams et al., 2021).…”

The Relationship Between Resting Cerebral Blood Flow, Neurometabolites, Cardio-Respiratory Fitness and Aging-Related Cognitive Decline

“…In recent years, research shows that cerebrovascular control and its integration with other physiological systems (such as cardiovascular and pulmonary) play a key role in improved brain functioning via rehabilitation programs ( 60 ). Aerobic exercise is an important rehabilitation approach that can non-pharmacologically invoke cardiovascular responses that improve cerebrovascular function ( 61 ) (for example, CBF), and neurophysiology ( 62 , 63 ) (i.e., GABA and glutamate).…”