Subarachnoid trabeculae suppress cerebrospinal fluid pressurization during translational impact loading using instrumented biomimetic head surrogates

Traumatic brain injury (TBI) is a global health concern. Cerebrospinal fluid (CSF) dynamics play a key role in the injury process but remain poorly understood due to experimental challenges imposed by the opaque skull and subarachnoid trabeculae (SAT). This study investigates the influence of SAT on CSF pressurization during impact using instrumented head surrogates. Two surrogates were developed, each including a transparent plastic skull, artificial brain tissue, and a CSF layer between. One model incorporated artificial SAT (permeability = 2.12 ± 1.03 × 10⁻⁹ m², porosity = 0.97), while the control model lacked SAT. Both models were instrumented with pressure sensors in the coup and contrecoup regions and subjected to repeated translational impacts monitored with an accelerometer. Results reveal that the presence of SAT structure decreased peak pressure in both coup and contrecoup regions. Across peak linear impact accelerations (126 g to 1071 g on the surrogate frame, corrected to 68 g to 574 g on the surrogate skull) with impact durations of 0.5 ms to 1.1 ms, linear regressions of peak pressure (P_max) vs. impact acceleration (α) revealed that SAT reduced the slope by 33 % in the coup region (P_max = 0.0006α without SAT, P_max = 0.0004α with SAT), and by 60 % in the contrecoup region (P_max = 0.0054α without SAT, P_max = 0.0022α with SAT). In the contrecoup region, pressurization was rapid but delayed by 24 % relative to that of coup region, suggesting possible occurrence of local intracranial cavitation and SAT's potential interactions with cavitation bubbles. In summary, this study uncovers the biomechanical function of SAT in modulating pressure dynamics during impact, indicating a protective effect that may mitigate brain injury. STATEMENT OF SIGNIFICANCE: This study provides new insights into how the fibrous structures around the brain, known as subarachnoid trabeculae (SAT), help protect against traumatic brain injury (TBI). While previous TBI studies attribute injury to tissue deformation during impact, this work considers the overlooked role of cerebrospinal fluid (CSF) pressure dynamics within the skull. Using transparent head surrogates equipped with pressure and acceleration sensors, SAT influence on CSF pressurization is directly measured for a reduction in harmful pressure spikes. Findings reveal a previously unrecognized protective mechanism in brain biomechanics. By replicating head anatomy, this work advances modern understanding of brain injury and could guide the development of future helmets, medical models, and injury prevention strategies.