The importance of brain thermomechanics in clinical neurosurgery and simulations

During surgery, the exposed brain can experience temperatures from physiological levels down to room or preservation temperatures. Research on the effects of temperature on brain mechanics is limited, and studies relevant to surgical conditions have largely focused on reporting empirical results without further mechanical interpretation. To our knowledge, a comprehensive, model-based analysis of thermal effects on the mechanical response of brain tissue under conditions resembling surgery is still lacking. This study aims to fill the long-standing gap by quantifying undercharacterized thermo-frequency-dependent aspects of brain tissue and providing temperature-sensitive, model-ready properties for surgical conditions. To this end, oscillatory shear tests were performed on bovine brain tissue at 1 % strain across a frequency range of 0.1-100 rad/s and at three temperatures: 5 °C, representing hypothermic preservation, and 25 °C and 35 °C, approximating the room and physiological temperature range, respectively. A Generalized Maxwell model was fitted to present viscoelastic parameters. Across most frequencies, experimental results showed that storage (G') and loss (G″) moduli decreased with increasing temperature, with 5 °C values significantly higher than those at higher temperatures, which were not significantly different. Fits to the model quantitatively parameterized the softening trend, showing a decrease in stiffness parameters with increasing temperature. Additionally, the model showed that the rise from hypothermic to room or physiological temperature reduced the viscous contribution and increased the elastic contribution, thereby altering the tissue's stress-relaxation behavior. This study provides a basis to improve computational analysis of brain tissue across temperatures, supporting improved modeling, simulations, and surgical planning.