Our auditory results using the Vibrant Soundbridge on the long process of the incus: 20 years of data

OBJECTIVE: After 20 years of experience with different types of middle ear implants, we analyzed our database about the Vibrant Soundbridge (VSB) to know the rate of complications, the effect on the residual hearing and the audiometric gain in our center.

METHOD: The study was retrospective and included all VSB implants bound to the long process of the incus in our tertiary medical center between january 1999 and february 2015. We observed the effect of surgery on residual hearing by comparing bone and air conduction thresholds before and after implantation. The functional results of the implant were quantified by measuring, at several post-operative intervals, the thresholds with the VSB in pure tone audiometry and speech audiometry, in quiet and in noise.

RESULTS: 53 VSB were implanted in 46 patients aged between 22 and 81 years old (average 53.9). 48 patients (90%) suffered from a sensorineural hearing loss, and 5 patients from a mixed hearing loss due to an otosclerosis (but only 3 of them have undergone stapedotomy). There were no major complications (e.g. facial palsy, dead ear or postoperative infection). The placement of the implant created an insignificant deterioration of the air conduction thresholds (5,6 dB HL) and bone conduction thresholds (2.2 dB HL) at 6 weeks post-implantation. The bone conduction thresholds increased by 4.7 dB HL 2.5 years after surgery in comparison with the preoperative results, which is also considered clinically insignificant. With the implant turned on, the pure tone audiometry thresholds in open field, in quiet, were significantly improved (gain of 13.9 dB on average on frequencies from 250 to 8000 Hz), particularly at frequencies of 1000, 2000 and 4000 Hz as the average gain on these frequencies amounted to 19.4 dB. The speech intelligibility in a cocktail party noise was also improved by 18.3% on average at 6, 52 and 104 weeks post-implantation.

CONCLUSION: The Vibrant Soundbridge with the electromagnetic vibrator fixed to the long process of the incus is a safe active middle ear implant with no major complications; it has no significant impact on the residual hearing. The VSB is particularly suitable for patients who are unable to wear conventional hearing aids due to anatomical or infectious problems in the external ear canal, or in case of poor audiometric results with conventional hearing aids. The VSB brings significant hearing gain, as it is particularly efficient in frequencies for the speech range and higher, resulting especially in better speech intelligibility in noisy environments.