A comparison of static and dynamic cerebral autoregulation during mild whole-body cold stress in individuals with and without cervical spinal cord injury: a pilot study

This paper was published in the journal Spinal Cord and the definitive published version is available at https://doi.org/10.1038/s41393-017-0021-7.Study design: Experimental study. Objectives: To characterize static and dynamic cerebral autoregulation (CA) of individuals with cervical spinal cord injury (SCI) compared to able-bodied controls in response to moderate increases in mean arterial pressure (MAP) caused by mild whole-body cold stress. Setting: Japan Methods: Five men with complete autonomic cervical SCI (sustained>5y) and six age-matched able-bodied men participated in hemodynamic, temperature, catecholamine and respiratory measurements for 60 min during three consecutive stages: baseline (10 min; 330C water through a thin-tubed whole-body suit), mild cold stress (20 min; 250C water) and post-cold recovery (30 min; 330C water). Static CA was determined as the ratio between mean changes in middle cerebral artery blood velocity and MAP, dynamic CA as transfer function coherence, gain and phase between spontaneous changes in MAP to middle cerebral artery blood velocity. Results: MAP increased in both groups during cold and post-cold recovery (mean differences: 5 to 10 mm Hg; main effect of time: p=0.001). Static CA was not different between the able-bodied vs the cervical SCI group (mean [95% CI] of between-group difference: -4 [-11 to 3] and -2 [-5 to 1] cm/s/mmHg for cold (p=0.22) and post-cold (p=0.24), respectively). At baseline, transfer function phase was shorter in the cervical SCI group (mean [95% CI] of between-group difference: 0.6 [0.2 to 1.0] rad; p=0.006), while between-group differences in changes in phase were not different in response to the cold stress (interaction term: p=0.06). Conclusions: This pilot study suggests that static CA is similar between individuals with cervical SCI and able-bodied controls in response to moderate increases in MAP, while dynamic CA may be impaired in cervical SCI due to disturbed sympathetic control

Brain imaging of neurovascular dysfunction in Alzheimer’s disease

Neurovascular dysfunction, including blood–brain barrier (BBB) breakdown and cerebral blood flow (CBF) dysregulation and reduction, are increasingly recognized to contribute to Alzheimer’s disease (AD). The spatial and temporal relationships between different pathophysiological events during preclinical stages of AD, including cerebrovascular dysfunction and pathology, amyloid and tau pathology, and brain structural and functional changes remain, however, still unclear. Recent advances in neuroimaging techniques, i.e., magnetic resonance imaging (MRI) and positron emission tomography (PET), offer new possibilities to understand how the human brain works in health and disease. This includes methods to detect subtle regional changes in the cerebrovascular system integrity. Here, we focus on the neurovascular imaging techniques to evaluate regional BBB permeability (dynamic contrast-enhanced MRI), regional CBF changes (arterial spin labeling- and functional-MRI), vascular pathology (structural MRI), and cerebral metabolism (PET) in the living human brain, and examine how they can inform about neurovascular dysfunction and vascular pathophysiology in dementia and AD. Altogether, these neuroimaging approaches will continue to elucidate the spatio-temporal progression of vascular and neurodegenerative processes in dementia and AD and how they relate to each other