Association Between Cerebral Blood Flow and Longitudinal Cerebral Microvascular Structure Changes in Moderate Traumatic Brain Injury Assessed by Transcranial Color-Coded Duplex Ultrasonography

Objectives: Microvascular injury after traumatic brain injury (TBI) is the basis for the occurrence of neurological dysfunction. This study aims to dynamically observe cerebrovascular hemodynamics using TCCD to evaluate the stability of the microcirculatory network before and after TBI. Methods: In this study, a moderate TBI model in rats was established, comprising a sham group and TBI groups at days 1 (1 d), 3 d, 5 d, 7 d, 10 d, 14 d, 21 d, and 35 d (n = 5), and each group underwent TCCD and pathological examinations. Examinations were conducted to acquire hemodynamic parameters for every subgroup. Importantly, vessel density (VDnorm), number of endpoints (NEPnorm), and average vessel diameter (AVDnorm) of the injured-side brain tissue to calculate the Microcirculation Structural Score (MSS) were quantified and normalized from histological brain sections, while intracranial vessel hemodynamic indicators including PI, were obtained by TCCD. We analyzed correlations between microcirculation parameters and vessel hemodynamic parameters to validate whether the PI reflects microcirculatory alterations after TBI. Results: This study found that 1–3 days post-TBI was the peak period of vascular injury. From 5 to 14 days, microvascular density and intracranial large vessel blood flow parameters recovered before the microcirculatory structure. From 21 to 35 days, microvessels continued to remodel, with AVDnorm negatively correlated with PI of middle cerebral artery cortical branches (MCAcb-PI) (r = −0.626, p < 0.001). Then, a weighted PI (PIindex) was constructed, which was positively correlated with the microcirculatory injury MSS (r = 0.592, p < 0.001). Conclusions: PIindex can quantitatively assess microcirculatory injury and vascular structural remodeling. TCCD serves as a simple and feasible novel tool to monitor microcirculatory changes after TBI.