Blast-induced mild traumatic brain injury through ear canal: A finite element study

Purpose: The role of ear canal in transmitting blast waves to the brain is not clear. The goal of this work is to characterize the influence of ear canal on blast-induced mild traumatic brain injury through a computational approach. Methods: A three-dimensional human head model with single-side ear canal details was reconstructed from computed tomography images. The ear canal was positioned either facing the incident blast wave or facing away from the blast wave. Results: The blast wave-head interaction has demonstrated that the overpressure within the ear canal was substantially amplified when the ear directly faced the blast wave. When it faced away from the blast wave, the overpressure within the ear canal was less than the actual incident blast pressure. Regardless of the substantial pressure differences within the ear canal induced by the blast wave, the resulting intracranial pressures were almost the same for both cases. Conclusions: The blast wave-head interaction has demonstrated that the role of the ear canal in brain dynamics, and thus brain injury, was negligible. However, the peak overpressure within the ear canal exceeded the documented tympanic membrane rupture and inner ear damage thresholds. This was speculated to cause the degeneration of axons along the auditory pathway up to the midbrain. This work provided fundamental understanding of the load transmission through the ear canal and could serve as a platform for designing better protective armors.