Human Histology after Structure Preservation Cochlear Implantation via Round Window Insertion

OBJECTIVES

Current surgical techniques aim to preserve intracochlear structures during cochlear implant (CI) insertion to maintain residual cochlear function. The optimal technique to minimize damage, however, is still under debate. The aim of this study is to histologically compare insertional trauma and intracochlear tissue formation in humans with a CI implanted via different insertion techniques.

METHODS

One recent temporal bone from a donor who underwent implantation of a full-length CI (576°) via round window (RW) insertion was compared with nine cases implanted via cochleostomy (CO) or extended round window (ERW) approach. Insertional trauma was assessed on H&E-stained histological sections. 3D reconstructions were generated and virtually re-sectioned to measure intracochlear volumes of fibrosis and neo-ossification.

RESULTS

The RW insertion case showed electrode translocation via the spiral ligament. 2/9 CO/ERW cases showed no insertional trauma. The total volume of the cochlea occupied by fibro-osseous tissue was 10.8% in the RW case compared with a mean of 30.6% (range 8.7%-44.8%, N = 9) in the CO/ERW cases. The difference in tissue formation in the basal 5 mm of scala tympani, however, was even more pronounced when the RW case (12.3%) was compared with the cases with a CO/ERW approach (mean of 93.8%, range 81% to 100%, N = 9).

CONCLUSIONS

Full-length CI insertions via the RW can be minimally traumatic at the cochlear base without inducing extensive fibro-osseous tissue formation locally. The current study further supports the hypothesis that drilling of the cochleostomy with damage to the endosteum incites a local tissue reaction.

LEVEL OF EVIDENCE

4: Case-control study Laryngoscope, 134:945-953, 2024.

Endoscope-Assisted Cochlear Implantation in Atretic Round Window

Different techniques have been proposed for cochlear implant (CI) from its conventional transmastoid posterior tympanotomy approach. Endoscopy role in the otologic field is still relatively new, but it provides a better surgical view with improved image clarity, especially in the challenging anatomical visualization of the critical structures in CI surgery. A 3-year-old girl with bilateral progressive profound hearing loss was scheduled for left cochlear implant surgery. The pre-operative high-resolution computed tomography (HRCT) of the temporal bone and magnetic resonance (MR) of internal acoustic meatus reported no significant abnormality of the middle and inner ears structures bilaterally. The standard left postauricular cortical mastoidectomy and posterior tympanotomy were performed. However, the microscopic view could not visualize the round window (RW) niche despite a widened extended posterior tympanotomy and surgical field manipulation. Transfacial recess endoscopic examination was done and was able to identify the possibly atretic RW. With endoscopic guidance, CI electrodes were inserted via cochleostomy, and intraoperative impedance measurement and neural response telemetry were obtained both during surgery and the postoperative phase. No intra- and postoperative complications were observed in this case. Following activation, the CI was functioning well. In conclusion, atretic RW is a rare anomaly found intraoperatively during CI surgery. Endoscope-assisted electrode insertion offers excellent visualization of targeted middle ear structures, especially in limited or abnormal anatomy of RW, which could minimize the risk of surgical complications.

Suspicion and Treatment of Perilymphatic Fistula: A Prospective Clinical Study

Background: Since the discovery of the perilymphatic fistula (PLF), the diagnosis and treatment remain controversial. If successfully recognized, the PLF is surgically repairable with an obliteration of the fistula site. Successful treatment has a major impact on patient's quality of life with an improvement in their audiological and vestibular symptoms. Objective: To prospectively investigate patients' clinical and audiological evolution with PLF suspicion after middle ear exploration and obliteration of the round and oval window. Study Design: Prospective comparative study. Setting: Tertiary care center. Methods: Patients were divided into two groups: Group I consisted of patients where no PLF had been identified intraoperatively at the oval and/or at the round window, and Group II consisted of patients where a fistula had been visualized. Patient assessment was a combination of past medical history, the presence of any risk factors, cochlear and vestibular symptoms, a physical examination, temporal bone imaging, audiograms, and a videonystagmogram (VNG). Results: A total of 98 patients were divided into two groups: 62 in Group I and 36 in Group II. A statistically significant difference regarding gender was observed in Group II (83.3% of males vs. 16.7% of females, p = 0.008). A total of 14 cases (4 and 10 in Groups I and II, respectively) were operated for a recurrent PLF. Fat graft material was used in the majority of their previous surgery; however, no difference was found when comparing fat to other materials. In addition, no statistically significant difference was noted between Groups I and II concerning predisposing factors, imaging, VNG, symptom evolution, or a physical exam before the surgery and at 12 months post-operative. However, both groups showed statistically significant hearing and vestibular improvement. On the other hand, the air conduction (AC) and bone conduction (BC) at each frequency were not statistically different between the two groups before surgery but showed statistically significant improvement at 12 months post-operatively, especially for the BC at the frequencies 250 (p = 0.02), 500 (p = 0.0008), and 1000 Hz (p = 0.04). Conclusions: Whenever you suspect a perilymphatic fistula, do not hesitate to explore middle ear and do window obliterations using a tragal perichondrium material. Our data showed that cochlear and vestibular symptoms improved whether a fistula had been identified or not.

The Value of Endoscopic Exposure of Round Window in Cochlear Implant via Facial Recess

Introduction  Cochlear implantation has been considered as the best treatment in patients with severe to profound hearing loss unaidable with hearing aids. The main value of endoscope-assisted cochlear implantation is improved visibility of the RW Objective  to assess the value of endoscopic assisted CI surgery via facial recess approach without elevating tympanic anulus. Methods  This Prospective case series study non-randomized sample was performed on 50 patients with severe to profound hearing loss unaidable with hearing aids undergoing unilateral endoscopic assisted cochlear implant surgery with round window electrode insertion Results  There were 23 male and 27 female patients. Most of the cases were children (41 cases). Of those 50 patients, 39 were prelingually hearing impaired. Four cases had various inner ear abnormalities. The standard mastoidectomy and Posterior Tympanotomy approach were used for all cases. Endoscopic identification of the RW through the PT enabled us to perform regular surgery in all cases. The current study concludes the difference between microscopic exposure and endoscopic exposure represented by Saint Tomas classification found that endoscopic exposure of round window classification is better represented by downgrading in the classification of round window exposure as type I 29(58%), type IIa 18(36%) type IIb 3 (6%) Non were type III by endoscopic exposure compared to microscopic exposure of round window is a type I 7(14%), type II 14(28%), type IIb 22(44%) and type III 7 (14%). Conclusion  Endoscopy proved a great value in exposure and identification of RW in CI surgery through posterior tympanotomy approach.

Localization of the Vertical Part of the Facial Nerve in the High-Resolution Computed Tomography During Pediatric Cochlear Implantation

BACKGROUND

This study proposed a classification of the vertical portion of the facial nerve (VPFN) location, incorporating the previous classifications regarding the posterior-to-anterior and medial-to-lateral dimensions. We also evaluated the implication of this proposed classification on the round window visibility during pediatric cochlear implantation (CI).

METHODS

It was a retrospective multicenter observational cohort study. This study included 334 cases that underwent CI between 2015 and 2022 at multiple referral institutes. Two physicians evaluated the preoperative computed tomography images of 334 patients and determined the radiological type of the VPFN. These types were matched with intraoperative round window accessibility.

RESULTS

The Spearman's correlation coefficient showed a strong correlation between the proposed VPFN type and the intraoperative round window visibility, as the P-value was <.001.

CONCLUSION

This classification could provide the surgeon preoperatively with the precise location of the VPFN in the lateral-to-medial and posterior-to-anterior dimensions. Furthermore, this location classification of the VPFN was significantly correlated with intraoperative round window accessibility, with an accuracy of 90.42%. Therefore, types C and D were expected to have difficult accessibility into the round window, and more surgical interventions were needed to modify the posterior tympanotomy or use other approaches.

Selected structures of middle ear relevant to cochlear implantation on the basis of computer tomography

BACKGROUND

The primary objective of this study was to analyze middle ear structures critical for cochlear implantation using computed tomography.

MATERIALS AND METHODS

Patients who underwent cochlear implantation at the Department of Otolaryngology in Szczecin between 2015 and 2022 were eligible for the study. We analyzed computed tomography images of 57 ears in 52 patients. The following parameters were assessed: mastoid aeration, tegmen tympani height, sigmoid sinus position, posterior tympanotomy width, the distance between the facial nerve and chorda tympani, modified facial recess distance, and the prediction line described by other authors.

RESULTS

In 69% of patients, after the removal of the round window bony overhang, the round window membrane became fully visible. There were no statistically significant correlations found for parameters describing mastoid process anatomy or those rating the width of the posterior tympanotomy concerning round window access. The prediction lines, according to Kashio and Jwair, were found to be relevant. In cases where patients' access to the niche and membrane of the window was rated as good or very good during clinical evaluation, they were more likely to describe the window as being located posteriorly or medially in the radiological evaluation. Using a binary Jwair scale provided a better correlation with the clinical assessment. In cases where the windows were graded as posterior, the clinical assessment indicated better surgical access, especially to the RWM (Round Window Membrane).

CONCLUSIONS

Evaluating middle ear anatomy on a computed tomography scan is useful for preparing for middle ear surgery but does not significantly affect the ability to access the round window. For such access, the position of the window in relation to the facial nerve is the most relevant factor, and measurements based on this relationship hold the highest clinical value.

Osteoneogenesis at the Round Window: A Possible Cause of Cochlear Implant Failure?

Surgery for cochlear implant is a traumatic procedure, with inflammatory responses leading to immediate and delayed intracochlear changes, resulting in newly formed fibrous and bony tissue. This newly formed tissue is thought to affect speech perception with cochlear implants and can also play a role in causing device malfunctioning and soft failures. We present a case of left cochlear implant explantation and reimplantation in a 15-year-old girl, who experienced deterioration of speech perception and device failure associated with osteoneogenesis of the round window, which could represent a cause of cochlear implant failure. To avoid surgical trauma of the cochlear lateral wall, enlarged round window insertion rather than a cochleostomy, soft surgical techniques, and the application of steroids are all important issues to prevent new tissue formation, although special attention should also be given to the trauma of round window borders.

Location of the Tympanic Nerve Relative to the Round and Oval Windows

BACKGROUND

The aim of the study was to measure the distance of the tympanic nerve to the oval window and round window niche in adult cadavers for evaluating its usability as an anatomical landmark during middle ear-related surgeries, including stapedotomy and cochleostomy, and for preventing its iatrogenic damage during surgical practices such as otosclerosis surgery and cochlear implantation.

METHODS

The middle ears of 10 adult cadavers aged 74.70 ± 14.56 years were bilaterally dissected with the help of an endoscope and microscope to measure the distance of tympanic nerve to round window niche and oval window.

RESULTS

Tympanic nerve was found as 1.60 ± 0.86 mm (range, 0-3.11 mm) and 1.55 ± 0.38 mm (range, 1.04-2.20 mm) away from round window niche and oval window, respectively. In relation to the quantitative values of these 2 distances, neither right-left nor male-female significant differences were determined (P > .05). Tympanic nerve was observed in all temporal bones. In terms of the shape and twigs of tympanic nerve, extreme variations among cadaveric temporal bones were determined. Tympanic nerve-round window niche distance between 0-1 mm was defined as type 1 (20%), between 1 and 2 mm as type 2 (45%), between 2 and 3 mm as type 3 (30%), and between 3 and 4 mm as type 4 (5%).

CONCLUSION

Tympanic nerve may be vulnerable at round window niche- or oval window-related surgeries (e.g., cochleostomy).

Landmarks for Proper Round Window Electrode Insertion in Cochlear Implantation

BACKGROUND

This study aimed to evaluate the role of landmarks for proper round window electrode insertion in cochlear implantation surgery.

METHODS

This is a case series study. We included 150 patients undergoing cochlear implantation in a tertiary medical center during the period from January to December 2019. Patients with inner ear malformations or ossification or revision surgery were excluded. Three surgeons partici- pated in the study. During surgery, the round window electrode insertion was marked using 5 surgical landmarks: oval window, pyramid, fustis, round window membrane, and arborization of intracochlear blood vessels. Each surgeon reported on the identification of each landmark and its reliability for round window electrode insertion.

RESULTS

Oval window and round window membrane were clearly seen by the 3 surgeons in all cases. Pyramid was seen in 94% of cases, fustis in 85%, and intracochlear wall in 90% of cases. The postoperative transorbital x-ray confirmed the intracochlear position of electrodes in all cases.

CONCLUSION

Round window electrode insertion can be precisely performed using these 5 surgical landmarks in straight forwards cases as well as in difficult cases. These landmarks can also assist in teaching young surgeons, in a step-wise manner, how to properly do round window electrode insertion in cochlear implantation surgery.

A Window of Opportunity: Perilymph Sampling from the Round Window Membrane Can Advance Inner Ear Diagnostics and Therapeutics

In the clinical setting, the pathophysiology of sensorineural hearing loss is poorly defined and there are currently no diagnostic tests available to differentiate between subtypes. This often leaves patients with generalized treatment options such as steroids, hearing aids, or cochlear implantation. The gold standard for localizing disease is direct biopsy or imaging of the affected tissue; however, the inaccessibility and fragility of the cochlea make these techniques difficult. Thus, the establishment of an indirect biopsy, a sampling of inner fluids, is needed to advance inner ear diagnostics and allow for the development of novel therapeutics for inner ear disease. A promising source is perilymph, an inner ear liquid that bathes multiple structures critical to sound transduction. Intraoperative perilymph sampling via the round window membrane of the cochlea has been successfully used to profile the proteome, metabolome, and transcriptome of the inner ear and is a potential source of biomarker discovery. Despite its potential to provide insight into inner ear pathologies, human perilymph sampling continues to be controversial and is currently performed only in conjunction with a planned procedure where the inner ear is opened. Here, we review the safety of procedures in which the inner ear is opened, highlight studies where perilymph analysis has advanced our knowledge of inner ear diseases, and finally propose that perilymph sampling could be done as a stand-alone procedure, thereby advancing our ability to accurately classify sensorineural hearing loss.

[The significance of microanatomy of the round window in terms of cochlear implantation]

Sensoneural hearing loss is a polyetiological disease, which is often a secondary reflection of systemic pathology and is associated with damage of the cochlea and auditory nerve receptors. An important point in the surgical stage of cochlear implantation is the introduction of an implant active electrode into the cochleostomy spiral channel through the cochleostoma or round window. However, the issue of intra-cochlear structures surgical trauma in such surgical intervention seems to be very important, as it may reduce the success of subsequent rehabilitation. Therefore, the study of the anatomy of the round window and adjuscent areas was the objective of this work.

Radiological classification of the mastoid portion of the facial nerve: impact on the surgical accessibility of the round window in cochlear implantation

BACKGROUND

Mastoid portion of the facial nerve plays an important role in the round window approach of cochlear implantation.

OBJECTIVES

This study aimed to predict the anterior displacement of the mastoid portion of the facial nerve in the preoperative HRCT coronal cuts. We also aimed to detect the implication of anterior displacement of MPFN on the R.W. accessibility through the posterior tympanotomy during cochlear implantation.

MATERIALS AND METHODS

It was a retrospective observational cohort study in tertiary referral hospitals. We included 246 pediatric patients who underwent cochlear implantation due to bilateral severe to profound SNHL through a posterior tympanotomy approach.

RESULTS

Type I MPFN was present in 84 cases, type II MPFN was present in 149 patients, and type III MPFN was present in 13 cases. R.W. was inaccessible in 3 cases with MPFN type II and in 11 subjects with MPFN type III. There was a statistically significant difference regarding the R.W. accessibility between the three types of MPFN (p-value <.05). There was a strong statistically significant correlation between R.W. accessibility and the radiological type of the MPFN.

CONCLUSION

Mandour radiological classification of the mastoid portion of the facial nerve in the preoperative HRCT coronal offers an easily applicable method to detect the anterior displacement of the facial nerve by using easy and well-known landmarks. This classification can also predict R.W. accessibility through posterior tympanotomy during cochlear implantation with 97.97% accuracy.

Prognostic Value of Trial Round Window Stimulation for Selection of Candidates for Cochlear Implantation as Treatment for Tinnitus

Electrical stimulation with cochlear implants is able to significantly suppress the tinnitus sensations in 25–72% of implanted patients. Up to this point, no clear predictors for the effectiveness of tinnitus suppression with cochlear implants have been found and this substantially limits the possibility of the application of cochlear implants for this purpose. The objective of the study was to investigate if a trial electrical round window stimulation (RWS) could be used as a diagnostic tool for identifying candidates in whom electrical stimulation would be successful as treatment for tinnitus. Thirty-four patients with unilateral severe tinnitus and ipsilateral moderate to severe sensorineural hearing loss underwent a trial RWS under local anesthesia. Thirteen patients received a cochlear implant. All patients qualified for cochlear implantation on the basis of the trial RWS showed tinnitus suppression with the implant switched on. Complete or almost complete tinnitus suppression was obtained in 77% and partial in 23%. The mean tinnitus loudness reduction was 68% (VAS score reduction from 7.7 to 2.5). False negative results are estimated not to exceed 10–15%. We conclude that significant tinnitus suppression achieved during trial RWS under local anesthesia is a simple procedure allowing the efficient identification of candidates in whom electrical stimulation with a cochlear implant would be successful as treatment for intractable tinnitus.

The Effects of Round Window Membrane Injury and the Use of a Model Electrode Application on Hearing in Rats

OBJECTIVE

To investigate the effects of the mechanical trauma to the round window, a model electrode inserted into the scala tympani on the cochlear reserve, and the efficacy of topical steroids in preventing hearing loss.

MATERIALS AND METHODS

21 male Wistar Albino rats were equally categorized into three groups. In all groups an initial mechanical injury to round window was created. Only subsequent dexamethasone injection was administrated into the cochlea in the subjects of group 2 while a multichannel cochlear implant guide inserted into the cochlea prior to dexamethasone administration for group 3. Distortion product otoacoustic emissions (DPOAEs) were obtained prior to and immediately after the surgical injury, eventually on postoperative seventh day (d 7). Mean signal/noise ratios (S/Ns) obtained at 2000, 3000, and 4000 Hz were calculated. Data sets were compared with non-parametric statistical tests.

RESULTS

The early intraoperative mean S/Ns were significantly less than preoperative measurements for group 1 and 2; however, preoperative and postoperative d 7 average S/Ns did not differ. There was statistically significant difference between preoperative, intraoperative and postoperative d 7 average S/Ns for group 3.

CONCLUSION

We observed that hearing was restored approximately to the preoperative levels following early postoperative repair. However, an electrode insertion into the cochlea via round window subsequent to mechanical trauma seems to cause a progressive hearing loss. Therefore, a special care must be taken to avoid the injury to the round window membrane in the course of the placement of a cochlear implant electrode and surgery for the chronic otitis media.

Anatomy of the Round Window Region With Relation to Selection of Entry Site Into the Scala Tympani

OBJECTIVES/HYPOTHESIS

The aim of cochlear implantation is to safely insert an electrode array into the scala tympani (ST) while avoiding damage to surrounding structures. There is disagreement on the optimal way of entering the ST-the round window (RW) approach versus cochleostomy. Regardless of the chosen approach, it is vital to understand the regional anatomy, which is complex, difficult to conceptualize, and rarely dissected in temporal bone courses. The goal of this study was to examine the anatomy of the RW to gain more in-depth knowledge on the local relationships of the anatomical structures and propose an approach for entering the ST in cochlear implant surgery tailored to the encountered anatomy.

STUDY DESIGN

Cadaveric prevalence study and expert opinion with literature review.

METHODS

Cadaveric temporal bone dissection (n = 13) by the first author assessing the RW anatomy.

RESULTS

The round window membrane (RWM) and the osseous spiral lamina (OSL) are curved structures, each with a horizontal and a vertical part. The two horizontal portions are very closely apposed. The relationship between the OSL and the RWM determines the best site for a cochleostomy, which if required is best placed anteroinferiorly to the RWM. The distance between the oval window inferior margin and the RW membrane is less than 2 to 3 mm. The ST initially extends inferiorly and medially to the RW.

CONCLUSIONS

The findings of our dissection have implications for cochlear implant surgery in aiming to avoid trauma to the OSL and basilar membrane and aid decision making in choosing the safest surgical approach.

LEVEL OF EVIDENCE

5. Laryngoscope, 131:E598-E604, 2021.

Effect of Round Window Opening Size on Residual Hearing Preservation in Cochlear Implantation

OBJECTIVES

This study aims to compare the hearing preservation outcomes in cochlear implant surgery following slit versus full opening of the round window membrane.

SETTING

Tertiary referral center.

STUDY DESIGN

Comparative study.

SUBJECTS AND METHODS

Seventy patients (mean, 26.3 years; range, 2-69 years) who underwent cochlear implantation via the round window approach were included in the study. Thirty-five subjects were prospectively enrolled for cochlear implantation via the open round window technique between August 2018 and January 2019. Thirty-five patients who underwent cochlear implantation from January 2017 to July 2018 via the slit round window opening, frequency matched by sex and age, were retrospectively enrolled. Pre- and postoperative thresholds were obtained. The percentage of hearing preservation was computed with the HEARRING Network formula and classified into complete, partial, and minimal hearing preservation. The results between the groups were compared and analyzed at 6 months postoperatively.

RESULTS

The rate of complete hearing preservation in the open group was statistically significant (P = .030) at 71.4% (n = 25) as compared with 45.7% (n = 16) in the slit group.

CONCLUSIONS

The widely opened round window may be an optional technique that surgeons can utilize to improve hearing preservation outcomes.

Dye Tracking Following Posterior Semicircular Canal or Round Window Membrane Injections Suggests a Role for the Cochlea Aqueduct in Modulating Distribution

The inner ear houses the sensory epithelium responsible for vestibular and auditory function. The sensory epithelia are driven by pressure and vibration of the fluid filled structures in which they are embedded so that understanding the homeostatic mechanisms regulating fluid dynamics within these structures is critical to understanding function at the systems level. Additionally, there is a growing need for drug delivery to the inner ear for preventive and restorative treatments to the pathologies associated with hearing and balance dysfunction. We compare drug delivery to neonatal and adult inner ear by injection into the posterior semicircular canal (PSCC) or through the round window membrane (RWM). PSCC injections produced higher levels of dye delivery within the cochlea than did RWM injections. Neonatal PSCC injections produced a gradient in dye distribution; however, adult distributions were relatively uniform. RWM injections resulted in an early base to apex gradient that became more uniform over time, post injection. RWM injections lead to higher levels of dye distributions in the brain, likely demonstrating that injections can traverse the cochlea aqueduct. We hypothesize the relative position of the cochlear aqueduct between injection site and cochlea is instrumental in dictating dye distribution within the cochlea. Dye distribution is further compounded by the ability of some chemicals to cross inner ear membranes accessing the blood supply as demonstrated by the rapid distribution of gentamicin-conjugated Texas red (GTTR) throughout the body. These data allow for a direct evaluation of injection mode and age to compare strengths and weaknesses of the two approaches.

"Third Window" and "Single Window" Effects Impede Surgical Success: Analysis of Retrofenestral Otosclerosis Involving the Internal Auditory Canal or Round Window

Background and Objectives: We aimed to identify prognostic computed tomography (CT) findings in retrofenestral otosclerosis, with particular attention paid to the role of otosclerotic lesion area in predicting post-stapedotomy outcome. Materials and Methods: We included 17 subjects (23 ears) with retrofenestral otosclerosis who underwent stapedotomy. On preoperative CT, the presence of cavitating lesion and involvement of various subsites (cochlea, round window [RW], vestibule, and semicircular canal) were assessed. Pre- and post-stapedotomy audiometric results were compared according to the CT findings. The surgical outcomes were analyzed using logistic regression with Firth correction. Results: Cavitating lesions were present in 15 of 23 ears (65.2%). Involvement of the RW was the strongest predictor of unsuccessful surgical outcome, followed by involvement of the internal auditory canal (IAC) and the cochlea. Conclusions: RW and IAC involvement in retrofenestral otosclerosis were shown to predict unsuccessful outcomes. While a “third window” effect caused by extension of a cavitating lesion into the IAC may dissipate sound energy and thus serve as a barrier to desirable postoperative audiological outcome, a “single window” effect due to an extension of retrofenestral otosclerosis into the RW may preclude a good surgical outcome, even after successful stapedotomy, due to less compressible cochlear fluid and thus decreased linear movement of the piston.

[Round window niche area anatomy in terms of cochlear implantation]

Cochlear implantation is the most effective method of rehabilitation of patients with a high degree of hearing loss and deafness. This is a complex, multi-stage way of rehabilitation that includes selection of candidates for surgical intervention, a surgical stage and postoperative long-term auditory rehabilitation. In carrying out the surgical stage of cochlear implantation the round window niche area is of great interest, since the variability of its anatomical features affects the access to scala tympani. The article presents the data obtained from study of the round window niche area anatomy on cadaveric temporal bones. Variations of structures important for cochlear implantation have been determined.

Endoscopic-Assisted Cochlear Implantation in Children with Malformed Ears

OBJECTIVE

Complex middle and inner ear malformations are considered an important limitation for cochlear implant (CI) with traditional microscopic techniques. The aim of the present study is to describe the results of the endoscopic-assisted CI procedure in children with malformed ears.

STUDY DESIGN

Case series with chart review of consecutive patients.

SETTING

Two tertiary referral centers: University Hospital of Verona and University Hospital of Modena, Italy.

SUBJECTS AND METHODS

In total, 25 children underwent endoscopic-assisted cochlear implantation between January 2013 and January 2018. The audiologic and neuroradiologic assessment showed profound hearing loss and malformation of the middle and inner ear in all children. A complete review of anatomic features, surgical results, and audiologic outcomes was performed. The surgical technique is described step-by-step, and the outcomes are detailed.

RESULTS

All patients (mean age, 3.6 years; range, 2.8-9 years) underwent a transattical/endoscopic-assisted CI procedure. All children showed varying degrees of auditory benefit, as measured by routine audiometry, speech perception tests, and Categories of Auditory Performance scores (mean, 6). No immediate or late postoperative complications were noted.

CONCLUSION

The endoscopic-assisted approach proved to be successful in cochlear implantation. The direct visualization and magnification allow (1) exploration of the tympanic cavity; (2) confirmation of all anatomic features, with strict control of the course of the facial nerve, round window area, and inner ear; and (3) performance of the cochleostomy with adequate insertion of the array.

Bone conduction hearing in the blockage of oval and/or round windows in cats

BACKGROUND

Simple or non-syndromic types of oval window (OW) or round window (RW) atresia are relatively rare in clinical. Few studies have assessed bone conduction (BC) hearing in OW or RW atresia patients, with some reporting that BC hearing lies within the normal range, whereas others observing impaired BC hearing.

AIMS/OBJECTIVES

This study explored the effect of blocking the OW and RW during BC in cat models.

MATERIAL AND METHODS

Twenty-four cats were randomly divided into three immobilization groups (OW blockage, RW blockage, and OW + RW blockage) and control group. Each immobilization group also had the initial control state before blockage. Medical adhesive and ear mould glue were used to immobilise the stapes footplate and RW, respectively. Comparisons were made of the auditory brainstem response (ABR) thresholds before and after immobilization for the three immobilization groups during three different stimuli [air conduction (AC) click, BC click, and BC pure tones].

RESULTS

The AC click thresholds increased after immobilisation in three experimental groups compared to the control group (p < .05). The AC click thresholds increased compared to their initial control state after all three immobilization groups (p < .05). With an increase in frequency from 2 to 8 kHz, there was a general decrease in the difference between pre- and post-immobilization BC hearing thresholds in all three immobilization groups. The BC click threshold and BC tone thresholds at 2-4 kHz in both OW blockage and OW + RW blockage groups exceeded those in RW blockage group (p < .05).

CONCLUSIONS AND SIGNIFICANCE

The use of medical adhesive and ear mould glue for the blockages of OW and RW, respectively in cats was feasible. The effect of blocking the OW and RW in BC hearing was larger at low frequencies than high frequencies between 2 and 8 kHz. OW blockage had a greater effect than RW blockage on BC hearing at 2-4 kHz range.

Tinnitus Treatment Using Noninvasive and Minimally Invasive Electric Stimulation: Experimental Design and Feasibility

Noninvasive transcranial or minimally invasive transtympanic electric stimulation may offer a desirable treatment option for tinnitus because it can activate the deafferented auditory nerve fibers while posing little to no risk to hearing. Here, we built a flexible research interface to generate and control accurately charge-balanced current stimulation as well as a head-mounted instrument capable of holding a transtympanic electrode steady for hours. We then investigated the short-term effect of a limited set of electric stimulation parameters on tinnitus in 10 adults with chronic tinnitus. The preliminary results showed that 63% of conditions of electric stimulation produced some degree of tinnitus reduction, with total disappearance of tinnitus in six subjects in response to at least one condition. The present study also found significant side effects such as visual, tactile, and even pain sensations during electric stimulation. In addition to masking and residual inhibition, neuroplasticity is likely involved in the observed tinnitus reduction. To translate the present electric stimulation into a safe and effective tinnitus treatment option, we need to optimize stimulation parameters that activate the deafferented auditory nerve fibers and reliably suppress tinnitus, with minimal side effects and tolerable sensations. Noninvasive or minimally invasive electric stimulation can be integrated with sound therapy, invasive cochlear implants, or other forms of coordinated stimulation to provide a systematic strategy for tinnitus treatment or even a cure.

Surgeon Oriented Preoperative Radiologic Evaluation in Cochlear Implantation - Our experience with a Proposed Checklist

Introduction  Preoperative temporal bone imaging studies have been routinely performed prior to cochlear implantation. Radiologists need to report these examinations with special focus on the surgeon's expectations. Objectives  To provide a basic structured format, in the form of a checklist, for reporting preoperative computed tomography (CT) and to its clinical impact on operative findings. Methods  The preoperative temporal bone CT scans of 47 patients were analyzed and reported according to the proposed checklist. Intraoperative assessment of mastoidectomy, posterior tympanotomy and round window access was done by the surgeon in a blinded fashion and were correlated with the radiological findings to assess its significance. Results  The proposed radiological checklist was reliable in assessing operative difficulty during cochlear implantation. Contracted mastoid and lower tegmen position were associated with a greater difficulty of the cortical mastoidectomy. Presence of an air cell around the facial nerve (FN) was predictive of easier facial recess access exposure. Facial nerve location and posterior external auditory canal (EAC) wall inclination were predictive of difficult round window (RW) accessibility. Conclusion  Certain parameters on the preoperative temporal bone CT scan may be useful in predicting potential difficulties encountered during the key steps involved in cochlear implant surgery.

[The effect of preload and support's stiffness on the performance of round window stimulation: a numerical analysis]

To investigate the influence of the preload and supporting stiffness on the hearing compensation performance of round window stimulation, a coupling finite model composed of a human ear, an actuator and a support was established. This model was constructed based on a complete set of micro-computed tomography (Micro-CT) images of a healthy adult's right ear by reverse engineering technology. The validity of the model was verified by comparing the model's calculated results with experimental data. Based on this model, we applied different amplitude preloads on the actuator, and changed the support's stiffness. Then, the influences of the actuator's preload and the support's stiffness were analyzed by comparing the corresponding displacements of the basilar membrane. The results show that after applying a preload on the actuator, its hearing compensation performance was increased at the middle and high frequencies, but was deteriorated at low frequencies; besides, compared with using the fascia as the actuator's support in clinical practice, utilizing the titanium alloy to fabricate the support would enhance the hearing compensation performance of the round window stimulation in the whole frequency range.

Surgical anatomy of the round window-Implications for cochlear implantation

BACKGROUND

The round window is an important portal for the application of active hearing aids and cochlear implants. The anatomical and topographical knowledge about the round window region is a prerequisite for successful insertion for a cochlear implant electrode.

OBJECTIVE OF REVIEW

To sum up current knowledge about the round window anatomy and to give advice to the cochlear implant surgeon for optimal placement of an electrode.

TYPE OF REVIEW

Systematic Medline search.

SEARCH STRATEGY

Search term "round window[Title]" with no date restriction. Only publications in the English Language were included. All abstracts were screened for relevance, that is a focus on surgical anatomy of the round window. The search results were supplemented with hand searching of selected reviews and reference lists from included studies.

EVALUATION METHOD

Subjective assessment.

RESULTS

There is substantial variability in size and shape of the round window. The round window is regarded as the most reliable surgical landmark to safely locate the scala tympani. Factors affecting the optimal trajectory line for atraumatic electrode insertion are anatomy of the round window, the anatomy of the intracochlear hook region and the variable orientation and size of the cochlea's basal turn.

CONCLUSIONS

The very close relation to the sensitive inner ear structures necessitates a thorough anatomic knowledge and careful insertion technique, especially when implanting patients with residual hearing. In order to avoid electrode migration between the scalae and to achieve protect the modiolus and the basilar membrane, it is recommended to aim for an electrode insertion vector from postero-superior to antero-inferior.

Surgical treatment of vertigo in cochlear implantees by electrode resealing

CONCLUSION

Our present findings demonstrate that resealing to cover the electrode is an effective method to treat vertigo after CI. An insufficient cochleostomy sealing can be regarded as a cause of postoperatively newly occuring vertigo after CI. A transtympanic revision is a promising treatment option in cases of post-operative dizziness. Intoduction: A well-known and frequently reported complication after cochlear implantation is the appearance of postoperative vertigo symptoms. The aim of the present study was to observe if the postoperatively new occurrence of vertigo can be treated by resealing of the round window patch after cochlear implantation.

MATERIAL AND METHODS

A retrospective analysis revealed that 10 patients underwent revision surgery transtympanally. Vertigo was assessed preoperatively and directly postoperatively and after 6 month after revision surgery by using the Dizziness Handycap Inventory (DHI).

RESULTS

The most common symptom was rotating vertigo. A spontanous nystagmus was seen in four cases. No nystagmus was found after the revision surgery. In three cases, the onset of dizziness was associated with an event (sneezing, otitis media, climbing a mountain). A preoperative CT showed insuspectible results in seven patients but revealed pathologies two patients. Vertigo was improved significantly in six patients, and three of them were symptom-free.

Round window stimulation with the Vibrant Soundbridge: Comparison of direct and indirect coupling

OBJECTIVES/HYPOTHESIS

The purpose of this study was to measure the degree of coupling between the floating mass transducer (FMT) and the round window membrane (RWM) in patients with conductive and mixed hearing loss implanted with the Vibrant Soundbridge (VSB) device. The efficiency of direct and indirect coupling of the FMT to the RWM was compared by measuring differences between the initial prescription targets and the final settings of the VSB audio processor after fine-tuning.

STUDY DESIGN

Retrospective study.

METHODS

Investigation of a group of subjects with either conductive or mixed hearing loss implanted with the VSB, a device that uses a FMT coupled to the RWM. There were two subgroups: subjects in which coupling was direct (no interposed material) or indirect (interposed material). The functional gain, insertion gain, and compression characteristics of the device were measured to assess the efficiency of coupling and to investigate the proximity of the fitting to prescriptive targets.

RESULTS

Coupling for the subgroup with indirect coupling of the RWM was higher (better) than for the subgroup with direct coupling. The gain deviation from prescriptive targets was smaller for the subgroup with indirect coupling.

CONCLUSIONS

The coupling method can have an effect on the coupling efficiency and the final electroacoustic settings of the device. The prescription targets were not accurate for the majority of subjects from either subgroup. Indirect coupling appears to provide more effective stimulation of the cochlea.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:2843-2849, 2017.

Congenital oval or round window malformations in children: Surgical findings and results in 17 cases

OBJECTIVES/HYPOTHESIS

To prospectively evaluate surgical findings and hearing results in children undergoing surgery for congenital oval or round window malformations (class IV malformations).

STUDY DESIGN

A nonrandomized, nonblinded, case series of prospectively collected data.

METHODS

Fourteen consecutive pediatric patients who underwent 17 surgical procedures for congenital oval or round window malformations in a tertiary referral center were included. Postoperative pure-tone audiometry was available in 15 cases. The surgical technique for repair of the ossicular chain was dictated by the surgical findings at the time of surgery. The majority of the cases underwent ossiculoplasty using a Teflon piston, bucket-handle prosthesis, or total ossicular replacement prosthesis. Associated surgical techniques included malleus relocation and oval window drill-out procedure. The main outcome measures were preoperative and postoperative hearing status using four-frequency (0.5, 1, 2, and 4 kHz) audiometry. Air-conduction thresholds, bone-conduction thresholds, and air-bone gap were measured. Postoperative audiometry was performed at 3, 6, 9, 12, 18, and 24 months after surgery and at a yearly interval thereafter.

RESULTS

Postoperative air-bone gap closure to 10 dB or less was achieved in 47%. A postoperative air-bone gap closure to within 20 dB or less was achieved in 60%. Postoperative sensorineural hearing loss did not occur in this series.

CONCLUSIONS

Middle ear surgery for class IV abnormalities is feasible, but success percentages are much lower compared to other types of congenital ossicular malformations. Surgeons should be particularly careful in case of facial nerve abnormalities on computed tomography or during middle ear exploration.

LEVEL OF EVIDENCE

4 Laryngoscope, 126:2552-2558, 2016.

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.

Cochlear gene transfer mediated by adeno-associated virus: Comparison of two surgical approaches

OBJECTIVES/HYPOTHESIS

Gene therapy offers the possibility of delivering corrective genetic materials to the cochlea, potentially improving hearing. In animals, the most commonly used surgical methods for viral gene therapy delivery to the cochlea are the round window and the cochleostomy approaches. However, the patterns of viral infection and the effects on hearing have not been directly compared between these two approaches. In this study, we compare the patterns of cochlear infection and effects on hearing between these two surgical approaches using adeno-associated virus serotype 2/8 (AAV8) as the gene delivery vehicle.

STUDY DESIGN

Animal study and basic science research.

METHODS

One- to two-month-old CBA/J mice were used in this study. AAV8-green fluorescent protein (GFP) was delivered to the cochlea by either the round window or the cochleostomy approach (described below). Auditory brainstem response was used to examine hearing thresholds before and after surgery. Animals were examined at 1, 2, 3, and 4 weeks after surgery for the patterns of cochlear infection and hearing loss.

RESULTS

Cochlear gene transfer was successful through both surgical approaches. In both approaches, AAV8-GFP mostly infected the inner hair cells. There was occasional low-level infection of the outer hair cells and supporting cells. The two surgical approaches resulted in comparable viral infection efficiencies. The round window approach resulted in less surgical trauma, as indicated by hearing loss, than the cochleostomy approach.

CONCLUSIONS

Adeno-associated virus-mediated gene transfer to the cochlea can be accomplished using either the round window or the cochleostomy surgical approach. The round window approach resulted in less hearing loss compared to the cochleostomy approach.

LEVEL OF EVIDENCE

NA.

The Relationship Between Cochleovestibular Orientation, Age, and Sensorineural Hearing Loss: Implications for Cochlear Implantation

OBJECTIVES

To determine if spatial orientation of the cochlea within the temporal bone is related to age or sensorineural hearing loss (SNHL) and describe the implications for cochlear implantation.

METHODS

Five angles of cochlear orientation were determined from computed tomography (CT) imaging of the temporal bones in adults with (n = 55) and without (n = 27) sensorineural hearing loss (SNHL) and children with (n = 45) and without (n = 12) SNHL: facial recess versus basal turn, posterior semicircular canal versus basal turn, round window versus basal turn (axial view), round window versus basal turn (coronal view), and the cochlear axis versus the mastoid facial nerve.

RESULTS

All angles showed substantial variation between subjects and between ears. The angles between the round window and basal turn (coronal view) and the posterior semicircular canal and basal turn were significantly correlated with age for all subjects with SNHL (r = 0.22, P = .002 and r = 0.15, P = .03, respectively). Patients with SNHL had significantly more acute angles (46.6° vs 55.8°) between the round window versus basal turn (axial orientation) compared to controls (P < .001).

CONCLUSIONS

Cochlear orientation within the temporal bone changes with age and the degree of SNHL. These results suggest that the approach to the round window for electrode insertion might differ between children and adults.

Implementation of a direct install 3-pole type EM transducer in round window niche for implantable middle ear hearing aids

Since the 1980's, various types of implantable hearing aids using unique means for delivering acoustic power to the inner ear have been developed. Recently, implantable hearing aids that stimulate the round window by the middle ear transducer have received great attention because it reduces loading effect at the ossicular chain. In this study, we have implemented a direct install 3-pole type EM transducer in round window niche for implantable middle ear hearing aid. The 3-pole type EM transducer consists of two permanent magnets and three coils and exhibit structural features that minimize leakage flux, thereby permitting high efficiency and low magnetic field interference. The stapes velocity was measured using a laser Doppler vibrometer in response to the round window stimulation from the transducer. To verify the usefulness of the 3-pole type EM transducer, we compared the stapes vibration characteristics produced by the transducer and those from a sound source. The magnitude of stapes velocity due to the round window stimulation at 1 mArms was equivalent to that of stapes velocity at 94 dB SPL sound stimulation. Thus, the evaluation study shows that the 3-pole type EM transducer is suitable for implantable hearing devices.

Impact of electrode design and surgical approach on scalar location and cochlear implant outcomes

OBJECTIVES/HYPOTHESIS

Three surgical approaches: cochleostomy (C), round window (RW), and extended round window (ERW); and two electrodes types: lateral wall (LW) and perimodiolar (PM), account for the vast majority of cochlear implantations. The goal of this study was to analyze the relationship between surgical approach and electrode type with final intracochlear position of the electrode array and subsequent hearing outcomes.

STUDY DESIGN

Comparative longitudinal study.

METHODS

One hundred postlingually implanted adult patients were enrolled in the study. From the postoperative scan, intracochlear electrode location was determined and using rigid registration, transformed back to the preoperative computed tomography which had intracochlear anatomy (scala tympani and scala vestibuli) specified using a statistical shape model based on 10 microCT scans of human cadaveric cochleae. Likelihood ratio chi-square statistics were used to evaluate for differences in electrode placement with respect to surgical approach (C, RW, ERW) and type of electrode (LW, PM).

RESULTS

Electrode placement completely within the scala tympani (ST) was more common for LW than were PM designs (89% vs. 58%; P < 0.001). RW and ERW approaches were associated with lower rates of electrode placement outside the ST than was the cochleostomy approach (9%, 16%, and 63%, respectively; P < 0.001). This pattern held true regardless of whether the implant was LW or PM. When examining electrode placement and hearing outcome, those with electrode residing completely within the ST had better consonant-nucleus-consonant word scores than did patients with any number of electrodes located outside the ST (P = 0.045).

CONCLUSION

These data suggest that RW and ERW approaches and LW electrodes are associated with an increased likelihood of successful ST placement. Furthermore, electrode position entirely within the ST confers superior audiological outcomes.

LEVEL OF EVIDENCE

2b.

Consensus statement on round window vibroplasty

OBJECTIVE

This study aimed to review current knowledge regarding implantation of the Vibrant Soundbridge floating mass transducer (FMT) at the round window (round window vibroplasty) as well as to form a consensus on steps for a reliable, stable surgical procedure.

DATA SOURCES

Review of the literature and experimental observations by the authors.

CONCLUSION

Round window (RW) vibroplasty has been established as a reliable procedure that produces good and stable results for patients with conductive or mixed hearing loss. The experience gained over the past few years of the authors' more than 200 implantations has led to consensus on several key points: (1) a wide and bloodless access to the middle ear with facial nerve monitoring, (2) the careful and correct identification and exposure of the round window membrane, (3) a good setup for efficient energy transition of the FMT, namely, perpendicular placement of the FMT with no contact to bone and the placement of cartilage behind the FMT to create a preloaded "spring" function, and (4) 4 points of FMT fixation: a rim of the round window bony overhang left intact both anterior and posterior to the FMT, conductor link stabilization, and cartilage behind the FMT. In addition, the FMT should be covered with soft tissue.

Gentamicin administration on the stapes footplate causes greater hearing loss and vestibulotoxicity than round window administration in guinea pigs

Clinically, gentamicin has been used extensively to treat the debilitating symptoms of Mèniére's disease and is well known for its vestibulotoxic properties. Until recently, it was widely accepted that the round window membrane (RWM) was the primary entry route into the inner ear following intratympanic drug administration. In the current study, gentamicin was delivered to either the RWM or the stapes footplate of guinea pigs (GPs) to assess the associated hearing loss and histopathology associated with each procedure. Vestibulotoxicity of the utricular macula, saccular macula, and crista ampullaris in the posterior semicircular canal were assessed quantitatively with density counts of hair cells, supporting cells, and stereocilia in histological sections. Cochleotoxicity was assessed quantitatively by changes in threshold of auditory brainstem responses (ABR), along with hair cell and spiral ganglion cell counts in the basal and second turns of the cochlea. Animals receiving gentamicin applied to the stapes footplate exhibited markedly higher levels of hearing loss between 8 and 32 kHz, a greater reduction of outer hair cells in the basal turn of the cochlea and fewer normal type I cells in the utricle in the vestibule than those receiving gentamicin on the RWM or saline controls. This suggests that gentamicin more readily enters the ear when applied to the stapes footplate compared with RWM application. These data provide a potential explanation for why gentamicin preferentially ablates vestibular function while preserving hearing following transtympanic administration in humans.

Round window versus cochleostomy technique in cochlear implantation: histologic findings

HYPOTHESIS

Cochleostomy or round window enlargement techniques for cochlear implant electrode insertion result in more abnormal tissue formation in the basal cochlea and are more apt to produce endolymphatic hydrops than round window electrode insertion.

METHODS

Twelve temporal bones from implanted patients were examined under light microscopy and reconstructed with 3-dimensional reconstruction software to determine cochlear damage and volume of neo-ossification and fibrosis after electrode insertion. Amount of new tissue was compared between 3 groups of bones: insertion through the round window (RW), after enlarging the RW (RWE) and cochleostomy (Cochl). The probable role of the electrode was evaluated in each case with hydrops.

RESULTS

More initial damage occurred in the Cochl and RWE groups than in the RW group, and the difference was significant between RWE and RW in cochlear segment I (p < 0.026). The volume of new bone in Segment I differed significantly between groups (p < 0.012) and was greater in the RWE group than in either the Cochl or RW groups (post hoc p's < 0.035 and 0.019, respectively). Hydrops was seen in 5 cases, all in the Cochl and RWE groups. Blockage of the duct was because of new tissue formation in 4 of the 5 hydrops cases.

CONCLUSION

With the electrodes in this series, implantation through the RW minimized initial intracochlear trauma and subsequent new tissue formation, whereas the RW extension technique used at the time of these implantations produced the greatest damage. Future studies may clarify whether today's techniques and electrodes will produce these same patterns of damage.

Evaluation of intratympanic dexamethasone for treatment of refractory sudden sensorineural hearing loss

OBJECTIVE

To observe and compare the efficacy of intratympanic application of dexamethasone (DXM) for the treatment of refractory sudden sensorineural hearing loss (SSNHL), the DXM was given in three different ways: by tympanic membrane injection, by drip through a ventilation tube, and by perfusion through a round window catheter.

METHODS

We conducted a nonrandomized retrospective clinical trial involving 55 patients with refractory SSNHL. For 21 patients (the perfusion group), DXM (2.5 mg/0.5 ml) was perfused transtympanically through a round window catheter using an infusion pump for 1 h twice a day for 7 d giving a total amount of 35.0 mg. For 23 patients (the injection group), DXM (2.5 mg/time) was injected by tympanic membrane puncture at intervals of 2 d on a total of four occasions giving a total amount of 10.0 mg. For 11 patients (the drip group), DXM (2.5 mg/0.5 ml) was dripped via a ventilation tube placed by myringotomy, once on the first day and twice a day for the remaining 6 d giving a total amount of 32.5 mg. Thirty-two patients with refractory SSNHL who refused to undertake further treatments were defined as the control group. Hearing recovery and complications were compared among the groups. Hearing results were evaluated based on a four-frequency (0.5, 1.0, 2.0, 4.0 kHz) pure tone average (PTA).

RESULTS

Post-treatment audiograms were obtained one month after treatments were completed. The improvements in average PTA for the perfusion, injection, and drip groups were 9.0, 8.6, and 1.7 dB, respectively. Hearing improvement was significantly greater in the perfusion and injection groups than in the control group (1.4 dB) (P<0.05). In the perfusion group, 8 out of 21 patients (38.1%) had a PTA improvement of 15‒56 dB (mean 29.8 dB); in the injection group, 8 out of 23 patients (34.8%) had a PTA improvement of 16‒54 dB (mean 24.9 dB); in the drip group, 1 of 11 patients (9.1%) had a PTA improvement of 26.0 dB; in the control group, 3 out of 32 patients (9.4%) had a PTA improvement of 15‒36 dB (mean 14.9 dB).

CONCLUSIONS

Topical intratympanic application of DXM is a safe and effective method for the treatment of SSNHL cases that are refractory to conventional therapies.

Comparison of gentamicin distribution in the inner ear following administration via the endolymphatic sac or round window

OBJECTIVE/HYPOTHESIS

The distribution of gentamicin in the inner ear via the endolymphatic sac (ES) or round window (RW) routes was investigated.

STUDY DESIGN

Experimental study.

METHODS

A fluorescent gentamicin-Texas Red conjugate (GTTR) was adopted to visualize the gentamicin. Adult guinea pigs were treated with GTTR applied to the ES or RW, the animals were allowed to recover for 3 days, then confocal microscopy was used to observe and quantify GTTR distributions in cochlear and vestibular sensory epithelium.

RESULTS

When GTTR was applied via the ES, strong GTTR labeling was observed in the vestibule while little GTTR was detected in the cochlea (P < .0001). However, distinct GTTR fluorescence was observed in the cochlea and vestibule following RW application (P = .7967). There was less GTTR labeling in cochlea via ES application than through RW administration (P < .0001).

CONCLUSIONS

ES drug application may be preferable for the treatment of intractable Meniere's disease. Laryngoscope, 2010.

Evaluation of round window stimulation using the floating mass transducer by intracochlear sound pressure measurements in human temporal bones

HYPOTHESIS

Round window (RW) stimulation with a floating mass transducer (FMT) can be studied experimentally and optimized to enhance auditory transduction.

BACKGROUND

The FMT (MED-EL Vibrant Soundbridge) has been recently implanted in patients with refractory conductive or mixed hearing loss to stimulate the RW with varying degrees of success. The mechanics of RW stimulation with the FMT have not been studied in a systematic manner.

METHODS

In cadaveric human temporal bones, measurements of stapes velocity with laser vibrometry in response to FMT-RW stimulation were used to optimize FMT insertion. The effect of RW stimulation on hearing was estimated using simultaneous measurements of intracochlear pressures in both perilymphatic scalae with micro-optical pressure transducers. This enabled calculation of the differential pressure across the cochlear partition, which is directly tied to auditory transduction.

RESULTS

The best coupling between the FMT and RW was achieved with a piece of fascia placed between the RW and the FMT, and by "bracing" the free end of the FMT against the hypotympanic wall with dental impression material. FMT-RW stimulation provided differential pressures comparable with sound-induced oval window stimulation greater than 1 kHz. However, less than 1 kHz, the FMT was less capable.

CONCLUSION

Measurements of stapes velocity and intracochlear sound pressures in scala vestibuli and scala tympani enabled experimental evaluation of FMT stimulation of the RW. The efficacy of FMT-RW coupling was influenced significantly by technical and surgical factors, which can be optimized. This temporal bone preparation also lays the foundation for future studies to investigate multiple issues of relevance to both basic and clinical science such as RW stimulation in stapes fixation, nonaerated middle ears, and third-window lesions, and to answer basic questions regarding bone conduction.