Transcutaneous and percutaneous bone conduction sound propagation in single-sided deaf patients and cadaveric heads

Objective: To investigate transcranial transmission (TT) and the dampening effect of the skin in patients and cadaver heads. Design: In patients a pure tone bone conduction audiogram for ipsilateral and contralateral stimulation was performed. The TT was defined as the difference between ipsilateral and contralateral hearing thresholds. In cadaver heads ipsilateral and contralateral promontory motion was measured using a three-dimensional Laser Doppler Vibrometer system. Study sample: Seven single-sided deaf patients fitted with a Baha® Connect, fifteen single-sided deaf patients without a bone conduction hearing aid and five Thiel-embalmed cadaver heads were included. Results: The TT decreased with increasing frequency in patients and cadaver heads. No significant difference was seen between patients and cadaver heads. Measurements on patients and cadaver heads showed increasing skin attenuation with increasing frequency. However, the dampening effect was 3-12 dB higher in patients than in cadavers at all frequencies. Conclusion: The TT was not significantly different for patients compared to cadaver heads. The value of promontory motion to estimate TT in patients need to be further evaluated. The skin attenuates a BC stimulus by 10-20 dB in patients and by a smaller amount in cadaver heads, probably due to changes in the properties of the Thiel-conserved skin. Keywords: Transcranial transmission; bone conduction; promontory motion; skin dampening; unilateral hearing loss