Enhanced dynamic cerebral autoregulation and impaired vasoreactivity may contribute to white matter damage in hypertension: A correlational tractography and transcranial Doppler study.

Hypertension (HT) is the leading risk factor for cerebral small vessel disease (CSVD). White matter lesions (WML) linked to CSVD are visible on conventional neuroimaging, likely reflecting late irreversible stages of the CSVD pathological cascade. Despite the prevalence of this disease, the mechanistic link between CSVD, hypertension and WML remains poorly understood. In this prospective, cross-sectional study, 44 hypertensive patients asymptomatic of CSVD underwent diffusion-weighted magnetic resonance imaging (dMRI) and transcranial Doppler (TCD) monitoring of the right middle and left posterior cerebral arteries (MCA and PCA, respectively) to assess dynamic cerebral autoregulation (dCA) and vasomotor reactivity to CO (VRCO). Diffusion measures from two dMRI models quantified the WM structural integrity: fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity from diffusion tensor imaging (DTI), and quantitative anisotropy (QA) and isotropy from q-space diffeomorphic reconstruction (QSDR). We examined the association of dMRI measures with dCA and VRCO through correlational tractography. We observed that impaired VRCO was associated with decreased WM structural integrity, indicated by the associations of reduced QA and increased MD and RD with lower VRCO. Regarding dCA, we found a negative association between QA and the phase parameter, indicating an increased dCA in association with reduced WM structural integrity. Our results suggest that HT-induced remodeling of the cerebrovasculature, with enhanced dCA and impaired VRCO, may contribute to impaired brain function and lead to CSVD, and highlight the potential of integrating TCD studies and dMRI, including QSDR-derived metrics, to investigate the natural progression of CSVD from its early, asymptomatic stages.