Multi-component and multi-frequency tympanometry: a comparison between cochlear implanted ear and non-implanted ear

Cochlear implant (CI) surgery may alter middle ear structure and function, potentially affecting the measurement of the electrically evoked stapedius reflex threshold (eSRT). This study aimed to investigate such alterations using multi-component and multi-frequency tympanometry. Specific objectives were to compare tympanometric findings, multi-component tympanogram patterns, and frequency-dependent changes in admittance (ΔY), susceptance (ΔB), conductance (ΔG), and phase angle (Δθ) between implanted and contralateral non-implanted ears.

Twenty-two paediatric participants with unilateral CI (Cochlear Nucleus CI422 with CP802 processor), aged 3.5-7 years, were included. Tympanometric assessments were performed using probe tones of 226 Hz, 678 Hz, and 1000 Hz to record admittance, susceptance, and conductance. Multi-component tympanograms were classified according to the Vanhuyse model. Multi-frequency tympanometry was conducted using the sweep-frequency method (250-2000 Hz, in 50 Hz steps). Parameters ΔY, ΔB, ΔG, and Δθ across frequencies were compared between implanted and non-implanted ears.

The implanted ears showed significant reductions in static admittance and elevations in resonant frequency compared to non-implanted ears (p < 0.05). At 1000 Hz, 5 of 22 implanted ears (22.7 %) demonstrated the 3B1G pattern, compared with 11 of 22 (50 %) non-implanted ears. Frequency-dependent decreases in ΔY, ΔB, ΔG, and Δθ were also significant in implanted ears (p < 0.05).

CI surgery is associated with frequency-dependent changes in the implanted ear, indicating altered mechano-acoustical properties of the middle ear and increased stiffness. These changes may influence clinical procedures, particularly eSRT measurement.