Cavitation in translational brain impacts: The role of cerebrospinal fluid pressure and brain deformation dynamics

Traumatic brain injury (TBI) affects an estimated 69 million people worldwide annually and is associated with neurological disability. However, injury mechanisms and outcomes remain poorly understood, limiting protective and treatment strategies. The pressure response of cerebrospinal fluid (CSF) has gained attention due to evidence of intracranial cavitation. However, the severity of CSF pressurization remains unexplored. This study introduces an experimental system to examine CSF flow during translational impacts on the head by analyzing brain strain distribution, CSF pressurization, and skull acceleration responses. A head surrogate filled with a hydrogel brain model and a CSF-like medium was subjected to free-fall impacts recorded with an accelerometer, and intracranial pressures were measured at the coup (site of impact) and the contrecoup (opposite of impact). Results revealed that the contrecoup experienced significantly higher peak pressures, reaching 4.3 MPa at 544g, primarily due to cavitation. The coup displayed lower pressures, reaching 0.3 MPa at 550g. Strain analysis showed that the contrecoup exhibited the highest minimum principal strain (ϵmin), indicating greater susceptibility to compression and damage. A linear relationship between impact acceleration (a) and peak pressure (P) was observed in the coup (P = 0.0006a, R2 = 0.97) and the contrecoup (P = 0.0054a, R2 = 0.91), with more variability demonstrated in the contrecoup due to inconsistent formation and growth of cavitation bubbles. These findings suggest that cavitation plays a crucial role in TBI and helps localize damage. Understanding CSF cavitation may support protective technologies and pressure management strategies aimed at reducing injury progression, potentially lowering the risk of neurodegenerative conditions following TBI.