The Influence of Incudostapedial Joint Separation on the Middle Ear Transfer Function

OBJECTIVES: One of the risks in middle ear surgery is high frequency hearing loss. It is believed that manipulations on the middle ear ossicles with the instruments may cause overstimulation of the inner ear and damage of the hear cells. Controversy arises whether temporary separation of the ossicles has any impact on middle ear transfer function and hearing threshold after surgery. The aim of the study is to evaluate the influence of incudostapedial joint (ISJ) separation on middle ear function in an experimental model. METHODS: With the use of single point laser Doppler vibrometer (LDV) stapes velocity in the intact chain and after ISJ separation was measured in 5 fresh human cadaver temporal bones. RESULTS: In all cases there was a decrease in stapes velocity after ISJ separation. Mead stapes velocity was reduced for 1 dB in 800 Hz to 9 dB in frequencies above 1,000 Hz. The decrease of velocity was greater in higher frequencies. CONCLUSION: Separation of the ISJ does not reduce significantly the middle ear function.