Effect of Skull Sutures on Vibrational Response of a Simplified Head Model
Authors: Cites Marianne E. , Dumm Christopher M. , Klinzing George E. , Balaban Carey D. , Vipperman Jeffrey S. 
Published: January 2025

Traumatic brain injury (TBI) is a frequently studied cause of death and disability. Car crash, contact sports, and combat injuries are typical scenarios for investigating the effects of blunt force and acceleration/deceleration impacts. A related area of study investigates damage arising from pressure wave exposure, such as blast wave injuries. However, the subfield of acoustic wave exposure is distinct from auditory damage arising in loud workplace environments, where noise exposure, following conventional, well characterized pathways, is related to hearing loss, neurodegenerative decline, and dementia.

This work bridges the gap between these two distinct injury mechanism fields (traumatic brain injury and noise-induced injury) by investigating how occupational noise exposure might induce traumatic brain injury. More specifically, this work investigates if sutural connections between the bones of the skull affect the vibrational properties of the head, ultimately revealing the possibility for a new type of brain injury mechanism.

The skull constituents surround and protect the brain. In typical head injury models, the skull is often treated as a continuous shell of compact bone, which in some studies includes the diploë (the spongy marrow-containing bone layer within the inner and outer layers of compact bone). However, the sutures that connect the skull bones are typically not modeled. Recent work has indicated that the skull may have unanticipated resonant vibrational properties if the sutures permit relative motion between the various skull bones. If so, the skull may be responsive to loud airborne sounds, and transmit higher-than-expected sound levels to the brain. Such oscillatory vibrations could induce alternating strains in intracranial tissues and be a potential mechanism for brain damage.

A typical analysis framework involves creating computational models of human anatomy and then analyzing their response to an injury event using finite element (FE) methods. Accuracy of numerical results is fundamentally reliant on the level of anatomic detail in the head model. More accurate anatomic features can enhance accuracy of the analysis, but the conclusions are then less generalizable to a population (e.g., a unique individual versus all humans).

In this study, we consider a simplified skull model containing the eight cranial bones (frontal, parietal, temporal, occipital, sphenoid, ethmoid) connected via cartilaginous sutural networks and a thin, protective dural layer on the inside skull surface. We use engineering simulation to investigate the effects sutures may have on overall skull vibrational response relative to the vibrational response of a conventional “continuous” skull for a prototypical skull size and shape. A series of sutural elastic moduli are investigated. The elastic modulus heavily influences the relative motion between the cranial bones, hence the resonant response. Results include natural frequencies and mode shapes corresponding to these properties. These results are expected to be applicable in occupational safety studies considering risk of injury in loud environments (where sound pressure levels in the range of 90–130 dB exist).