Importance of adhesiolysis in revision surgery for vibrant soundbridge device failures at the short incus process

Influence of skin flap thickness on the transmission characteristics of middle ear implant audio processors

OBJECTIVE

To measure signal transmission characteristics for audio processors of an active middle ear implant as a function of skin flap thickness, i.e., distance between audio processor and the implant's receiver coil.

METHODS

Output sound pressure levels for 90 dB input sound pressure level (OSPL90), reference test gains as function of frequency for an input sound pressure level of 60 dB (RTG60), and reference test gains (RTG - high frequency averages) were recorded in a hearing aid test box for Samba 2 Hi, Samba 2 Lo, and AP404 audio processors (MED-EL, Innsbruck, Austria) positioned on an implant-in-the-box and distances of 0-10 mm between audio processors and the receiver coil.

RESULTS

For all audio processors, the OSPL90 and RTG decreased linearly with increasing distance. The effect was dependent on audio processor type and the strongest reduction was observed for Samba 2 Lo. Between distances of 0 mm and 10 mm, the relative change of RTG was - 9,9 dB for Samba 2 Hi, -10,3 dB for AP404, and -27,7 dB for Samba 2 Lo.

CONCLUSIONS

Skin thickness is a clinically significant factor which has to be considered in VSB treatment. In combination with insufficient transducer coupling or in patients with hearing thresholds close to the indication criteria limit, a thick skin flap could lead to loss of transmitted energy resulting in insufficient audiological outcome with the active middle ear implant.

Device failure caused by the dissociation of floating mass transducer in Vibrant SoundBridge®

BACKGROUND

Vibrant SoundBridge® (VSB), a semi-implantable middle ear device, is one of the treatment options for patients with mild-to-severe sensorineural hearing loss or mixed hearing loss. Herein, we report delayed device failure after VSB surgery in two patients.

CASE PRESENTATION

In both cases, a revision surgery was performed for the removal of the device; dissociation of the floating mass transducer (FMT) and coupler was noticed in one patient, and dissociation of the FMT-coupler complex from the short process of the incus in the other. In Case 1, the vibration-like sounds disappeared after the surgery. In Case 2, wearing bilateral hearing aids improved hearing after removal surgery, but complaints regarding speech discrimination persisted. Both cases show the importance of not loosening the connectivity between the FMT, coupler, and short process of the incus during VSB surgery.

CONCLUSIONS

To our knowledge, there has been no report of dissociation from the short process of the incus or the dissociation between an FMT and the coupler.

Intraoperative quantification of floating mass transducer coupling quality in active middle ear implants: a multicenter study

Purpose

Evaluating the effectiveness of intraoperative auditory brainstem responses (ABRs) to stimulation by the Vibrant Soundbridge (VSB) active middle ear implant for quantifying the implant’s floating mass transducer (FMT) coupling quality.

Methods

In a diagnostic multicentric study, patients (> 18 years) who received a VSB with different coupling modalities were included. Pre- and postoperative bone conduction thresholds, intraoperative VSB-evoked ABR thresholds (VSB-ABR) using a modified audio processor programmed to preoperative bone conduction thresholds, postoperative vibrogram thresholds, and postoperative VSB-ABR thresholds were measured. Coupling quality was calculated from the difference between the pure tone average at 1000, 2000, and 4000 Hz (3PTA) vibrogram and postoperative 3PTA bone conduction thresholds.

Results

Twenty-three patients (13 males, 10 females, mean age 56.6 (± 12.5) years) were included in the study. Intraoperative VSB-ABR response thresholds could be obtained in all except one patient where the threshold was > 30 dB nHL. Postoperatively, an insufficient coupling of 36.7 dB was confirmed in this patient. In a Bland–Altman analysis of the intraoperative VSB-ABRs and coupling quality, the limits of agreement exceeded ± 10 dB, i.e., the maximum allowed difference considered as not clinically important but the variation was within the general precision of auditory brainstem responses to predict behavioral thresholds. Five outliers were identified. In two patients, the postoperative VSB-ABR thresholds were in agreement with the coupling quality, indicating a change of coupling before the postoperative testing.

Conclusion

The response thresholds recorded in this set-up have the potential to predict the VSB coupling quality and optimize postoperative audiological results.

A retrospective European multicenter analysis of the functional outcomes after active middle ear implant surgery using the third generation vibroplasty couplers

Purpose

To evaluate the safety and performance of three novel vibroplasty couplers that allow attachment of the floating mass transducer of a transcutaneous active middle ear implant (AMEI) to the round window (RW) membrane, the long process (LP), or the incus body and the short process (SP) of the incus.

Methods

Retrospective multicenter cohort study of 25 AMEI users with sensorineural or mixed hearing loss that were among the first implanted with an AMEI vibrating ossicular prosthesis in combination with the third generation of vibroplasty couplers between 2014 and 2016. Main Outcome Measures were bone-conduction pure-tone and vibroplasty thresholds, postoperative aided sound field thresholds and postoperative aided word recognition score (WRS).

Results

Bone conduction threshold changes of more than 10 dB in 4PTA_BC were observed in two subjects. A mean improvement of 57.8% in speech recognition was observed with a mean WRS at 65 dB SPL improving from 14.8% (SD 21.9%) preoperatively to a mean aided score of 72.6% (SD 18.6%). Sound field thresholds improved from an average 4PTA_SF of 64.1 dB HL (SD 9.8 dB HL) to 37.0 dB HL (SD 8.9 dB HL), resulting in a mean functional gain of 27.1 dB. There was no significant difference in WRS or functional gain between the coupler types.

Conclusion

Initial experience shows that all three third generation vibroplasty couplers represent safe and efficient attachment options for the FMT allowing the surgeon to choose the coupling type based on the present pathology.