Impact of Parenchymal Hemorrhage on Internal Carotid Artery Wall Shear Stress in Post-Traumatic Vasospasm: A Dynamic Helical CTA Study

Background: Post-traumatic cerebral vasospasm (CVS) significantly worsens outcomes in moderate-to-severe traumatic brain injury (msTBI). While wall shear stress (WSS) modulates endothelial function, its state in post-traumatic CVS remains poorly understood. We aimed to assess supraclinoid internal carotid artery (ICA) WSS in msTBI patients with and without non-surgical parenchymal hemorrhage. Methods: This retrospective cohort study (2013–2024) included 85 adults with msTBI and angiographic CVS. Patients were divided into Group 1 (Marshall II-III, no hematoma; n=43) and Group 2 (Marshall IV, non-surgical parenchymal hemorrhage; n=42). Dynamic helical CT angiography (DHCTA) and Doppler ultrasound were performed 2–5 days post-injury. WSS in the ICA C7 segment was calculated using a Poiseuille-based formula incorporating mean CBFV and vessel radius. Results: ICA WSS significantly exceeded the reference range (0.82 ± 0.08 Pa) in both groups (p<0.001). In Group 2, WSS was significantly higher than in Group 1 (p<0.0001). Specifically, Group 2 ipsilateral WSS (64.4 ± 9.8 Pa) was significantly higher than both the contralateral side (49.3 ± 8.3 Pa; p=0.021) and the Group 1 mean (33.2 ± 7.5 Pa; p<0.0001). No significant age-WSS correlation was observed (p=0.72). Group 2 exhibited a trend toward worse clinical outcomes (GOS), though only moderate disability (GOS 4) showed a significant difference (p<0.05). Conclusions: Post-traumatic CVS in msTBI is associated with markedly elevated ICA WSS. The presence of parenchymal hemorrhage further amplifies this hemodynamic stress, potentially contributing to non-physiological microcirculatory remodeling. These findings suggest WSS could serve as a biomarker for secondary brain injury risk, necessitating individualized surgical and medical management.