Exploration of the dynamics of otic capsule and intracochlear pressure: Numerical insights with experimental...

The otic capsule and surrounding temporal bone exhibit complex 3D motion influenced by frequency and location of the bone conduction stimulus. The resultant correlation with the intracochlear pressure is not sufficiently understood, thus is the focus of this study, both experimentally and numerically. Experiments were conducted on six temporal bones from three cadaver heads, with BC hearing aid stimulation applied at the mastoid and classical BAHA locations across 0.1-20 kHz. Three-dimensional motions were measured on various skull regions, including the promontory and stapes. Intracochlear pressure was measured using a custom acoustic receiver. The experiment was digitally recreated by a custom finite element model (FEM), based on the LiUHead, with the addition of an auditory periphery. The Young's modulus of the cortical bone domain within the FEM was varied between 4, 8, and 20 GPa. The predicted differential intracochlear pressures aligned with experimental data for most frequencies, and showed that skull deformation, particularly in the otic capsule, depends on skull material properties. Both experimental and FEM results indicated that the otic capsule behaves as a rigid accelerometer, imposing inertial loads on cochlear fluids, even above 7 kHz. Future work should explore the solid-fluid interactions between the otic capsule and cochlear contents.