Consensus statement on round window vibroplasty

The influence of intraoperative auditory brainstem responses on vibroplasty coupling-quality and analysis of the impact of different fixation steps on the coupling

PURPOSE

The Vibrant Soundbridge (VSB) is an established active-middle-ear-implant for patients with moderate-to-profound hearing-loss. This surgery is referred to as "Vibroplasty". Sufficient transfer of the VSB's floating-mass-transducers (FMT) energy to the inner ear is a crucial factor influencing the coupling-quality (CQ). However, assessing CQ is hamper by two issues: the method of CQ-assessment itself and the method of FMT-fixation during Vibroplasty.

METHODS

This prospective study explored the influence of intraoperative auditory-brainstem-response (+ ABR) measurements and various fixation methods on postoperative CQ after Vibroplasty as compared to matched-patients after Vibroplasty without intraoperative ABR (-ABR). Propensity-score-matching was performed based on preoperative bone-conduction-pure-tone-average-3 (BC-PTA3) at 1-, 2- and 4 kHz. Primary outcome parameters were postoperative CQ-PTA3, intraoperative ABR threshold for various fixation methods and postoperative BC-PTA3.

RESULTS

A total of 28 patients were included, of which 14 were + ABR. Preoperative BC-PTA3, sex, age, and number of previous surgeries did not differ significantly between groups (all p > 0.301). Mean postoperative CQ-PTA3 was significantly better for + ABR (1.8 vs. 12.3 dB-HL; p = 0.006). Mean intraoperative ABR threshold was superior for cartilage-counter-bearing and cartilage-housing compared to additional fixation with injectable-platelet-rich- fibrin (53 vs. 56 & 57 dB-HL, respectively; p = 0.04; η2 = 0.33). Mean postoperative BC-PTA3 did not significantly differ between patients (41.4 vs. 41.8 dB-HL; p = 0.77). A total of 7% of the patients required intraoperative readjustment of the FMT based on unsatisfactory intraoperative ABR threshold.

CONCLUSION

Intraoperative ABR measurement resulted in significantly better postoperative CQ. Cartilage-counter-bearing and cartilage-housing were observed to have superior CQ. A total of 7% of the patients could be spared revision-Vibroplasty due to intraoperative ABR measurement.

Is Age a Limiting Factor for Audiological Results in Active Middle Ear Implants?

Active middle ear implants (AMEI) are implantable options for patients with sensorineural, conductive, or mixed hearing loss who are not good candidates for hearing aids. The aim of this study was to compare audiological, surgical, quality of life, and sound quality outcomes in adults <60 and ≥60 years receiving an AMEI. Twenty adult patients who underwent AMEI implantation were divided into two groups, <60 and ≥60 y. Preoperative tests included pure-tone average and speech discrimination score (SDS) at 65 dB for disyllabic words in quiet. Postoperative measures included AMEI-aided bone conduction threshold, free-field warble-tone threshold, and SDS at 65 dB for disyllabic words in quiet 12 months after the AMEI fitting. Subjective benefit was evaluated using the Nijmegen Cochlear Implant Questionnaire (NCIQ), Glasgow Benefit Inventory (GBI), and Hearing Implant Sound Quality Index (HISQUI19). Mean functional gain was 32 and 30 dB, and SDS at 65 dB improved from 19 to 95% and from 31 to 84% in the <60 and ≥60 y groups, respectively. All NCIQ domains improved following surgery, and all patients had a positive overall GBI score. The mean HISQUI19 score was 97 in both age groups. AMEIs are an effective hearing restoration method for older adults suffering from conductive or mixed hearing loss.

Round Window Stimulation of the Cochlea

Mixed hearing loss associated with a sensorineural component and an impaired conductive mechanism for sound from the external ear canal to the cochlea represents a challenge for rehabilitation using either surgery or traditional hearing amplification. Direct stimulations of the ossicular chain and the round window (RW) membrane have allowed an improved hearing in this population. The authors review the developments in basic and clinical research that have allowed the exploration of new routes for inner ear stimulation. Similar changes occur in the electrophysiological measures in response to auditory stimulation through the traditional route and direct mechanical stimulation of the RW. The latter has proven to be very effective as a means of hearing rehabilitation in a group of patients with significant difficulties with hearing and communication.

Effects of design and coupling parameters on the performance of electromagnetic transducers in round-window stimulation

Many studies have investigated factors contributing to large variations in the outcomes of round-window (RW) stimulation but most have focused on the floating mass transducer (FMT). To determine whether results for the FMT hold for a fixed-type transducer (FTT), this study constructs two coupled finite element models of the transducer and the human ear that incorporate the cochlear third windows and inner structures of these two electromagnetic transducers. We use these FE models of the human ear and transducers to investigate the influence of four design parameters and coupling conditions for the transducers, i.e., the support's Young's modulus, the coupling layer's cross sectional area and Young's modulus, and the transducer's cross sectional area. The results show that an increase in the support's Young's modulus reduces the output of the FMT but increases that of the FTT. Reducing the cross sectional area and Young's modulus of the coupling layer significantly increases the low-frequency response of the FMT but slightly reduces that of the FTT. Reducing the cross sectional area of the transducer increases the output of the FMT but reduces that of the FTT. This shows that inner structures of electromagnetic transducers should be considered in the optimal design parameters and coupling conditions for RW stimulation.

Systematic and audiological indication criteria for bone conduction devices and active middle ear implants

Certain patients with conductive or mixed hearing loss can benefit from bone-conduction hearing devices or active middle ear implants. Available devices differ in coupling site, energy transfer from the sound processor to the implant, and the active or passive actuator technology. The audiological benefit of those devices depends on the maximum stable power output and the noise floor of the device, the degree and expected stability of the sensorineural hearing loss and the coupling efficiency with the aim on achieving a minumum of 30-35 dB effective dynamic range. The choice of the device is often a trade-off between the optimal audiological solution with respect to the hearing loss, technical device-related parameters and the expected coupling efficiency, the optimal surgical solution with respect to patho-anatomical aspects, device dimensions and the coupling site, invasiveness or surgical risks, and other patient factors with respect to the patients' wish and expectations, social aspects, device usability and connectivity. This review article lists all currently available implantable and conventional bone-conduction hearing devices and active middle ear implants with respect to technical features like maximum power output, market availability, and the expected effective output dynamic range.

Drug distribution along the cochlea is strongly enhanced by low-frequency round window micro vibrations

The cochlea’s inaccessibility and complex nature provide significant challenges to delivering drugs and other agents uniformly, safely and efficiently, along the entire cochlear spiral. Large drug concentration gradients are formed along the cochlea when drugs are administered to the middle ear. This undermines the major goal of attaining therapeutic drug concentration windows along the whole cochlea. Here, utilizing a well-known physiological effect of salicylate, we demonstrate a proof of concept in which drug distribution along the entire cochlea is enhanced by applying round window membrane low-frequency micro vibrations with a probe that only partially covers the round window. We provide evidence of enhanced drug influx into the cochlea and cochlear apical drug distribution without breaching cochlear boundaries. It is further suggested that ossicular functionality is not required for the effective drug distribution we report. The novel method presented here of local drug delivery to the cochlea could be implemented when ossicular functionality is absent or impeded and can be incorporated in clinically approved auditory protheses for patients who suffer with conductive, sensorineural or mixed hearing loss.

[Coupling of active middle ear implants-biomechanical aspects]

Active middle ear implants or implantable hearing aids are used to treat sensorineural or combined hearing loss. Their coupling to the middle ear structures has a large impact on the success of rehabilitation. Practical issues such as the coupling site, influence of middle ear status, and forward and backward excitation of the inner ear are discussed in the context of biomechanics. For this purpose, experimental studies, model simulations, and current literature data are evaluated. The explanations are intended to contribute to a better understanding of certain procedures in hearing rehabilitation with active implants.

Long-Term Stability and Safety of the Soundbridge Coupled to the Round Window

Objective

The objective of the study was to demonstrate the long‐term outcomes of patients implanted with the active middle ear implant (AMEI) Vibrant Soundbridge (VSB) through coupling the floating mass transducer (FMT) to the round window (RW).

Methods

This retrospective study evaluated the short‐ and long‐term clinical performance (audiological outcomes) and safety (revisions/explantations) of the VSB coupled to the RW between 2013 and 2019 at the St. Pölten University Hospital, Austria. For the outcome analysis, the sample was divided into a short‐term examination group followed up for less than 12 months (<12 months) and a long‐term examination group followed up for more than 12 months (>12 months). Cumulative survival outcomes were separately analyzed for subjects with and without cholesteatoma.

Results

46 patients with an average long‐term follow‐up period of 31.43 months (13–75 months) were investigated. Complications requiring revision surgery were reported in total in seven patients with cholesteatoma (15.2%) and none in subjects without cholesteatoma (0%). Residual hearing was not affected by VSB surgery. Word understanding on the Freiburger monosyllabic speech test improved significantly at 65 dB (P < .0001) and 80 dB (P < .0001), and these outcomes were stable for long‐term follow up.

Conclusion

The VSB coupled to the RW is a safe implantation method for patients with conductive or mixed hearing loss. Hearing improvement was stable for the long‐term follow‐up up to 74 months. The revision rates are directly related to the underlying pathology of cholesteatoma (with radical cavity); thus, this special cohort requires additional counseling on potential complications.

Level of Evidence

4 (Case‐series) Laryngoscope, 131:E1434–E1442, 2021

Herald Cell: The Gateway to Posterior Tympanotomy-A Cadaveric Study

Posterior tympanotomy is the avenue to the facial recess of the middle ear from mastoid antrum. The entry into the facial recess in many cases is heralded by a distinct air cell before approaching the facial-chordal plane. The current study was undertaken to determine the prevalence of this 'Herald Cell' in an adult cadaveric population. It was a human cadaveric temporal bone dissection study. The bones were dissected to carry out cortical mastoidectomy and posterior tympanotomy using standard otologic drills under microscopic visualization (Leica M320 F12). Appropriate snapshots were taken to document the presence or absence of Herald cell. A total of 51 temporal bones were dissected (26 right, 25 left sided). The Herald cell was found to be present in 22 bones (43.1%). Herald cell, when present, is a convenient and reliable landmark to carry out a safe posterior tympanotomy.

Lysis of the long process of the incus secondary to Vibrant SounBridge® middle ear implants, treated with hydroxyapatite bone cement

We report two patients presenting with delayed complicationsafter Vibrant SounBridge® middle ear implant surgery: in both cases, a revision surgery was performed and lysis of the long process of the incus was highlighted. A re-assembly of the clip around the remaining long process of the incus was performed, associated with hydroxyapatite bone cement application, on the clip and the incudo-stapedial joint. Both patients had a satisfying result, with a mean follow up of 12 months.

Round and Oval Window Anatomic Variability: Its Implication for the Vibroplasty Technique

OBJECTIVE

The objective of this study is to evaluate the anatomical variability of round and oval window regions and its relationship with their closest structures, to determine its implication on the fitting and stabilization of the middle ear implant Vibrant Soundbridge.

METHODS

Variations of the anatomy of round and oval window regions were assessed in a total of 85 human dissected temporal bones. Afterward, we evaluated the adaptation and subsequent stabilization of the floating mass transducer (FMT) of the Vibrant Soundbridge in 67 cases in round window (RW) and in 22 cases in oval window (OW), and the influence that the variability of the different anatomical features examined had on this stabilization. We also assessed access and surgeon's view of the RW niche through the facial recess approach.

RESULTS

Stabilization of the FMT in the RW was achieved in 53 (79%) of the 67 cases; we found that the less favorable anatomical conditions for stabilization were: membrane smaller than 1.5 mm, presence of a high jugular bulb and a narrow or very narrow RW niche. Frequently, two or more of these conditions happened simultaneously. In seven cases (22%) access to the RW through facial recess approach did not allow positioning the FMT in place. OW stabilization succeeded in 18 (82%) of the 22 cases.

CONCLUSION

Round and oval window vibroplasty are difficult surgical techniques. To place the FMT directly on the OW may be easier as we do not have to drill the niche. In both regions there are some anatomical conditions that hinder fitting the FMT and even make it impossible. Once fitted, the main problem is to achieve good stabilization of the device.

Implantable hearing devices

Combined hearing loss is an essential indication for implantable hearing systems. Depending on the bone conduction threshold, various options are available. Patients with mild sensorineural deafness usually benefit from transcutaneous bone conduction implants (BCI), while percutaneous BCI systems are recommended also for moderate hearing loss. For combined hearing losses with moderate and high-grade cochlear hearing loss, active middle ear implants are recommended. For patients with incompatibilities or middle ear surgery, implants are a valuable and proven addition to the therapeutic options.

Influence of backside loading on the floating mass transducer: An in vitro experimental study

HYPOTHESIS

The vibration of the floating mass transducer (FMT) of a single active middle-ear implant (AMEI) is distinctly influenced by the properties of the material coupled to its back side.

BACKGROUND

In round window vibroplasty, the FMT needs to be padded against the surrounding bone opposite from the round window membrane. This represents one factor influencing its performance as a round window driver. Therefore, we examined the effects of different materials linked to the back side of an FMT on its vibration range.

METHODS

The back side of an FMT was glued to a silicone cylinder 1.0 mm in diameter and 1.0 mm - 1.5 mm in length and of 40A, 50A or 70A Shore hardness; to cartilage of equivalent size; or to a round window soft coupler (RWSC), all firmly fixed on a steel plate. The vibrations were determined by a laser Doppler vibrometer (LDV) measuring the velocity of the centre point on the front side of the FMT.

RESULTS

The materials on the back side of the FMT significantly influenced the vibration range of the FMT. The RWSC and silicone of 40A Shore hardness allowed for the highest detected velocities, while cartilage led to a distinct reduction similarly to 70A silicone.

CONCLUSION

The coupling on the back side of an FMT distinctly affects its vibration range. In this regard, the RWSC and silicone of 40A Shore hardness yield the least impairment of vibration. Thus, the RWSC may be a feasible option in round window vibroplasty when additionally connected to the FMT opposite from the round window membrane.

Multicenter Clinical Trial of Vibroplasty Couplers to Treat Mixed/Conductive Hearing Loss: First Results

Objective: To evaluate the safety and effectiveness of round window (RW), oval window (OW), CliP and Bell couplers for use with an active middle ear implant. Methods: This is a multicenter, long-term, prospective trial with consecutive enrollment, involving 6 university hospitals in Germany. Bone conduction, air conduction, implant-aided warble-tone thresholds and Freiburger monosyllable word recognition scores were compared with unaided preimplantation results in 28 moderate-to-profound hearing-impaired patients after 12 months of follow-up. All patients had previously undergone failed reconstruction surgeries (up to 5 or more). In a subset of patients, additional speech tests at 12 months postoperatively were used to compare the aided with the unaided condition after implantation with the processor switched off. An established quality-of-life questionnaire for hearing aids was used to determine patient satisfaction. Results: Postoperative bone conduction remained stable. Mean functional gain for all couplers was 37 dB HL (RW = 42 dB, OW = 35 dB, Bell = 38 dB, CliP = 27 dB). The mean postoperative Freiburger monosyllable score was 71% at 65 dB SPL. The postimplantation mean SRT50 (speech reception in quiet for 50% understanding of words in sentences) improved on average by 23 dB over unaided testing and signal-to-noise ratios also improved in all patients. The International Outcome Inventory for Hearing Aids (IOI-HA)quality-of-life questionnaire was scored very positively by all patients. Conclusion: A significant improvement was seen with all couplers, and patients were satisfied with the device at 12 months postoperatively. These results demonstrate that an active implant is an advantage in achieving good hearing benefit in patients with prior failed reconstruction surgery.

Anatomic measurements of the posterior tympanum related to the round window vibroplasty in congenital aural atresia and stenosis patients

CONCLUSIONS

With the aggravation of the external auditory canal malformation, the size of extra-niche fossa became smaller, providing concrete data and valuable information for the better design, selecting and safer implantation of the transducer in the area of round window niche. Three-dimensional measurements and assessments before surgery might be helpful for a safer surgical approach and implantation of a vibrant soundbridge.

OBJECTIVES

The aim of this study was to investigate whether differences exist in the morphology of the posterior tympanum related to the round window vibroplasty among congenital aural atresia (CAA), congenital aural stenosis (CAS), and a normal control group, and to analyze its effect on the round window implantation of vibrant soundbridge.

METHODS

CT images of 10 normal subjects (20 ears), 27 CAS patients (30 ears), and 25 CAA patients (30 ears) were analyzed. The depth and the size of outside fossa of round window niche related to the round window vibroplasty (extra-niche fossa)and the distances between the center of round window niche and extra-niche fossa were calculated based on three-dimensional reconstruction using mimics software. Finally, the data were analyzed statistically.

RESULTS

The size of extra-niche fossa in the atresia group was smaller than in the stenosis group (p < 0.05); furthermore, the size of extra-niche fossa in the stenosis group was smaller than that of the control group (p < 0.05). There was no statistically significant difference of the depth of extra-niche fossa among different groups.

MRI scanning in patients implanted with a round window or stapes coupled floating mass transducer of the Vibrant Soundbridge

Conclusion MRI examinations in patients with an alternatively coupled VSB can lead to unpleasant side-effects. However, the residual hearing was not impaired, whereas the hearing performance with the VSB was decreased in one patient which could be fixed by a surgical revision. Different experiences for the VSB 503 can be expected. Objective To investigate the in vivo effects of MRI scanning on the Vibrant Soundbridge system (VSB) with an alternatively coupled Floating Mass Transducer (FMT). Method Sixty-five VSB (502) implantees were included in this study. Of them, 42 questionnaires could be evaluated with the patients' statements about their medical, otological, and general condition before, during, and after an MRI scan which was indicated for different medical reasons, despite the previous implantation of an alternatively coupled Vibrant Soundbridge System. Results In four patients (9.5%), five MRI examinations were performed. These were done for different indications (e.g. knee and shoulder joint diagnostics). During the scanning, noise and subjectively perceived distortion of the implant were described. A deterioration of the hearing gain with the VSB in place was found in one patient. A decrease of the hearing threshold was not observed.

Subtotal petrosectomy and Codacs™: new possibilities in ears with chronic infection

Subtotal petrosectomy combined with obliteration of the tympanomastoid is a standard procedure to treat temporal bones in patients with radical cavity and chronic infections. Currently, patients with profound-to-severe sensorineural hearing loss are often fitted with cochlear implants. In the case of profound mixed hearing loss, active middle ear implants have been used successfully. The new Codacs™ system provides an effective treatment for patients with severe-to-profound mixed hearing loss; however, only aerated middle ears have been treated with this device. The question arises whether the Codacs™ can be implanted in patients with radical cavity or ears with chronic otorrhea. Of the 41 patients who were implanted with the Codacs™ at the department, 4 received the device after subtotal petrosectomy and obliteration with abdominal fat. Clinical and audiological results were assessed. The device was implanted without any complications in the obliterated subtotal petrosectomy. The preliminary results of the first two patients showed stable bone conduction thresholds and indicated improved speech intelligibility in quiet and noise. Implanting the Codacs™ device after subtotal petrosectomy and obliteration with abdominal fat has been proven to be a feasible and suitable procedure for patients with radical cavity or chronic otorrhea. The speech intelligibility outcome directly after activation was comparable to patients with aerated middle ears.