Round Window Occlusion Affects Bone Conduction in Cadaver Heads.

OBJECTIVE: To explore the feasibility of ear mold glue in the molding of round window occlusion (RWO) in cadaver heads and to study the effect on bone conduction (BC).

METHODS: Ten cadaver heads were selected to establish RWO model. Ear mold glue was used to immobilize round window niche. The vibration properties of the stapes footplate (VST) in response to the acoustic stimulation, and the vibration properties of the stapes footplate and cochlear promontory (VCP) in response to the B-71 stimulation were assessed by laser Doppler vibrometer in both pre-RWO and post-RWO.

RESULTS: The mean velocities of the stapes footplate in response to the acoustic stimulation in post-RWO were decreased significantly beyond 14 dB for frequency from 0.5k to 3k Hz and decreased beyond 11 dB for frequency above 4 kHz compared with pre-RWO (p<0.05). The stapes footplate relative velocity (VST/VCP) for pre-RWO and post-RWO conditions showed almost no difference (the difference was around 0.5 dB for 0.5k, 1k, 2k, 5k, 6k, and 7k Hz frequencies), except a slight decrease of around 1.5 dB at 3k and 8k Hz frequencies in post-RWO. However, the VST/VCP was a significant decrease of 1.7 dB at 4k Hz in post-RWO compared with Pre-RWO (p<0.05).

CONCLUSION: Ear mold glue was available for the immobilization of round window niche in cadaver heads. The RWO have an impact on the BC hearing threshold. The effect of RWO on the BC was similar to that of otosclerosis, but the feature frequency for the depressed BC threshold at 4k Hz.