Electrophysiological detection of electrode fold-over in perimodiolar cochlear implant electrode arrays: a multi-center study case series.

PURPOSE: It is important for the surgeon to determine the position of the CI electrode array during and after its placement within the cochlea. Most preferably, this should be within the scala tympani to obtain the best audiological outcome. Thus, misplacement into the scala vestibuli or tip fold-over should be prevented. Since there are different ways to ensure proper positioning of the electrode array within the scala tympani (e.g., intraoperative radiography, electrophysiological recordings), our study was aimed at detecting intraoperative electrophysiologic characteristics to better understand the mechanisms of those electrode tip fold-overs. MATERIAL AND METHODS: In a multi-centric, retrospective case-control series, patients with a postoperatively by radiography detected tip fold-over in perimodiolar electrodes were included. The point of fold-over (i.e., the electrode position) was determined and the intraoperative Auto-NRT recordings were analysed and evaluated. RESULTS: Four patients were found to have an electrode tip fold-over (out of 85 implantees). Significant changes of the Auto-NRT recordings were not detected. All tip fold-overs occurred in the most apical part of the electrodes. DISCUSSION: Cochlear implantation for hearing impaired patients plays a decisive role in modern auditory rehabilitation. Perimodiolar electrode arrays may fold over during the insertion and, hence, could have a negative impact on audiological outcome. Characteristic electrophysiologic changes to possibly predict this were not found in our series.

In vivo experiences with magnetic resonance imaging scans in Vibrant Soundbridge type 503 implantees.

OBJECTIVE: To observe the effects of magnetic resonance imaging scans in Vibrant Soundbridge 503 implantees at 1.5T in vivo. METHODS: In a prospective case study of five Vibrant Soundbridge 503 implantees, 1.5T magnetic resonance imaging scans were performed with and without a headband. The degree of pain was evaluated using a visual analogue scale. Scan-related pure tone audiogram and audio processor fitting changes were assessed. RESULTS: In all patients, magnetic resonance imaging scans were performed without any degree of pain or change in pure tone audiogram or audio processor fitting, even without a headband. CONCLUSION: In this series, 1.5T magnetic resonance imaging scans were performed with the Vibrant Soundbridge 503 without complications. Limitations persist in terms of magnetic artefacts.

Electrode design and insertional depth-dependent intra-cochlear pressure changes: a model experiment.

BACKGROUND: Preservation of residual hearing is one of the major goals in modern cochlear implant surgery. Intra-cochlear fluid pressure changes influence residual hearing, and should be kept low before, during and after cochlear implant insertion. METHODS: Experiments were performed in an artificial cochlear model. A pressure sensor was inserted in the apical part. Five insertions were performed on two electrode arrays. Each insertion was divided into three parts, and statistically evaluated in terms of pressure peak frequency and pressure peak amplitude. RESULTS: The peak frequency over each third part of the electrode increased in both electrode arrays. A slight increase was seen in peak amplitude in the lateral wall electrode array, but not in the midscalar electrode array. Significant differences were found in the first third of both electrode arrays. CONCLUSION: The midscalar and lateral wall electrode arrays have different intra-cochlear fluid pressure changes associated with intra-cochlear placement, electrode characteristics and insertion.

MRI-Based Estimation of Scalar Cochlear-Implant Electrode Position.

The position of the cochlear-implant electrode is important to audiological outcomes after cochlear implantation. The common technique to evaluate the intracochlear electrode's position involves the use of ionized radiation in MSCT, DVT, or flat-panel tomography (FPT). Recent advances in knowledge regarding the handling of MRI artifacts in cochlear implantees indicate that estimating the intracochlear electrode's position with an MRI could be possible. This study's aim was to evaluate the ipsilaterally position of electrodes using MRI at 1.5 T. In a retrospective study of 10 implantees with postoperative need for MRI scanning, we evaluated the intrascalar electrode's position using a T2-weighted sequence at 1.5 T. We compared the resulting estimate of the intracochlear position with the estimates from the postoperative FPT scan and the intraoperative NRT ratio. For each ear, the MRI-estimated scalar position corresponded with the estimated positions from the FPT and NRT ratio. For eight ears, a scala tympani's position was observed in the MRI. In one case, an electrode scalar translocation was found. In one case, the scala vestibuli's position was observed. Thus, MRI-based estimation of the scalar position of a cochlear-implant electrode is possible. Limitations to this method include implant-specific magnet and fixation configurations, which can cause complications.

Postoperative imaging of the internal auditory canal : Visualization of active auditory implants.

BACKGROUND: Assessment of the internal auditory canal (IAC) and cochlea is of central importance in neurotology. The artefacts and visibility of active auditory implants on magnetic resonance imaging (MRI) vary because of their specific magnetic components. Knowledge of the size of MRI artefacts and the options for handling them is important for the auditory rehabilitation of specific diseases (e. g., vestibular schwannoma). METHODS: The current article is a literature review. RESULTS: MRI assessment of the IAC and cochlea after surgical placement of an active auditory implant is feasible only with a percutaneous bone-anchored hearing aid (BAHA, Ponto). When specific factors (implant position and MRI sequence) are taken into consideration, these structures can be visualized even after cochlear implantation. Complications such as magnet dislocation and pain may occur. CONCLUSION: The possibility of assessing the IAC and cochlea by MRI is an important aspect that needs to be taken into consideration when planning the auditory rehabilitation of patients after acoustic neuroma surgery.

Prevalence and complications of MRI scans of cochlear implant patients : English version.

BACKGROUND: Cochlear implants (CI) are the preferred method of treatment for patients with severe to profound bilateral sensorineural hearing loss and unilateral deafness. For many years, because of the magnetic field applied during magnetic resonance imaging (MRI) examinations, MRI examinations were contraindicated for CI patients or feasible only under specific circumstances. MRI examinations of CI recipients entail complications and therefore preventive measures have to be considered. The aim of this study was to evaluate the prevalence of MRI scans in CI recipients and the occurrence of complications and furthermore to investigate the preventive measures taken in radiological daily routine. MATERIALS AND METHODS: A retrospective questionnaire was sent to 482 patients that received CIs from 1999-2013. Details of the MRI examination and subjective and objective incidents during and after the MRI scan were evaluated. RESULTS: A total of 204 CI recipients answered the retrospective questionnaire (42.3 %). Twenty patients (9.8 %) with 23 implants underwent a total of 33 MRI scans with their cochlear implant in place. In 16 cases the scanned region was the head (49 %). Preventive measures in the form of head bandages were taken in 20 cases (61 %). The most common complication was pain in 23 cases (70 %) and the most serious complication was the dislocation of the internal magnet in 3 cases (9 %). CONCLUSIONS: The number of CI recipients undergoing MRI scans is high. Possible complications and preventive measures attract too little attention in radiological daily routine.

[Postoperative imaging of the internal auditory canal : Visualization of active auditory implants. German version]. / Postoperative Bildgebung des inneren Gehörgangs : Darstellung aktiver auditorischer Implantate.

BACKGROUND: Assessment of the internal auditory canal (IAC) and the cochlea is of central importance in neurotology. The artefacts and visibility of the different types of active auditory implants in MRI vary, due to their specific ferromagnetic components. Knowledge of the size of MRI artefacts and the options for handling these is important for the auditory rehabilitation of specific diseases (e. g., vestibular schwannoma). METHODS: The current paper is a literature review RESULTS: MRI assessment of the IAC and cochlea after surgical placement of an active auditory implant is feasible only with a percutaneous bone-anchored hearing aid (BAHA, Ponto). When specific factors (implant position and MRI sequence) are taken into consideration, these structures can be visualized even after cochlear implantation. Complications such as magnet dislocation and pain may occur. CONCLUSION: The possibility of assessing the IAC and cochlea by MRI is an important aspect that needs to be taken into consideration when planning the auditory rehabilitation of patients after acoustic neuroma surgery.

Postinsertional Cable Movements of Cochlear Implant Electrodes and Their Effects on Intracochlear Pressure.

Introduction. To achieve a functional atraumatic cochlear implantation, intracochlear pressure changes during the procedure should be minimized. Postinsertional cable movements are assumed to induce intracochlear pressure changes. The aim of this study was to observe intracochlear pressure changes due to postinsertional cable movements. Materials and Methods. Intracochlear pressure changes were recorded in a cochlear model with a micro-pressure sensor positioned in the apical region of the cochlea model to follow the maximum amplitude and pressure gain velocity in intracochlear pressure. A temporal bone mastoid cavity was attached to the model to simulate cable positioning. The compared conditions were (1) touching the unsealed electrode, (2) touching the sealed electrode, (3) cable storage with an unfixed cable, and (4) cable storage with a fixed cable. Results. We found statistically significant differences in the occurrence of maximum amplitude and pressure gain velocity in intracochlear pressure changes under the compared conditions. Comparing the cable storage conditions, a cable fixed mode offers significantly lower maximum pressure amplitude and pressure gain velocity than the nonfixed mode. Conclusion. Postinsertional cable movement led to a significant pressure transfer into the cochlea. Before positioning the electrode cable in the mastoid cavity, fixation of the cable is recommended.

[Prevalence and complications of MRI scans of cochlear implant patients: German version]. / Häufigkeit und Komplikationen von MRT-Untersuchungen bei Cochlea-Implantat-Patienten: German version.

BACKGROUND: Cochlear implants (CI) are the preferred method of treatment for patients with severe to profound bilateral sensorineural hearing loss and unilateral deafness. For many years, because of the magnetic field during magnetic resonance imaging (MRI) examinations, MRI examinations were contraindicated for CI patients or feasible only under specific circumstances. MRI examinations of CI recipients entail complications and therefore preventive measures have to be considered. The aim of this study was to evaluate the incidence of MRI scans in CI recipients and the occurrence of complications, and furthermore to investigate the preventive measures taken in radiological daily routine. MATERIALS AND METHODS: A retrospective questionnaire was sent to 482 patients that received CIs from 1999-2013. Details of the MRI examination and subjective and objective incidents during and after the MRI scan were evaluated. RESULTS: A total of 204 CI recipients answered the retrospective questionnaire (42.3%). Twenty patients (9.8%) with 23 implants underwent a total of 33 MRI scans with their cochlear implant in place. In 16 cases the scanned region was the head (49%). Preventive measures in the form of head bandages were taken in 20 cases (61%). The most common complication was pain in 23 cases (70%) and the most serious complication was the dislocation of the internal magnet in 3 cases (9%). CONCLUSIONS: The number of CI recipients undergoing MRI scans is quite high. Possible complications and preventive measures attract too little attention in radiological daily routine.

Simultaneous Labyrinthectomy and Cochlear Implantation for Patients with Single-Sided Ménière's Disease and Profound Sensorineural Hearing Loss.

Objective. To investigate the treatment outcome of a simultaneous labyrinthectomy and cochlear implantation in patients with single-sided Ménière's disease and profound sensorineural hearing loss. Study Design. Prospective study. Method. Five patients with single-sided Ménière's disease with active vertigo and functional deafness were included. In all cases, simultaneous cochlear implantation combined with labyrinthectomy surgery was performed. The outcome has been evaluated by the Dizziness Handicap Inventory (DHI) and speech recognition. Results. The combined labyrinthectomy and cochlear implantation led in all patients to a highly significant reduction of dizziness up to a restitutio ad integrum. After activation of the cochlear implant and rehabilitation, a mean monosyllabic speech understanding of 69% at 65 dB was observed. Conclusion. For patients with single-sided Ménière's disease and profound sensorineural hearing loss the simultaneous labyrinthectomy and cochlear implantation are efficient method for the treatment of vertigo as well as the rehabilitation of the auditory system.

Intracochlear fluid pressure changes related to the insertional speed of a CI electrode.

INTRODUCTION: To preserve residual hearing the atraumaticity of the cochlea electrode insertion has become a focus of cochlear implant research. In addition to other factors, the speed of insertion is thought to be a contributing factor in the concept of atraumatic implantation. The aim of our study was to observe intracochlear fluid pressure changes due to different insertional speeds of an implant electrode in a cochlear model. MATERIALS AND METHODS: The experiments were performed using an artificial cochlear model. A linear actuator was mounted on an Advanced Bionics IJ insertional tool. The intracochlear fluid pressure was recorded through a pressure sensor which was placed in the helicotrema area. Defined insertions were randomly performed with speeds of 0.1 mm/sec, 0.25 mm/sec, 0.5 mm/sec, 1 mm/sec, and 2 mm/sec. RESULTS: A direct correlation between speed and pressure was observed. Mean maximum values of intracochlear fluid pressure varied between 0.41 mm Hg and 1.27 mm Hg. Conclusion. We provide the first results of fluid pressure changes due to insertional speeds of CI electrodes in a cochlear model. A relationship between the insertional speed and intracochlear fluid pressure was observed. Further experiments are needed to apply these results to the in vivo situation.

Intracochlear pressure changes due to round window opening: a model experiment.

To preserve residual hearing in cochlea implantation, the electrode design has been refined and an atraumatic insertion of the cochlea electrode has become one aspect of cochlea implant research. The opening of the round window can be assumed to be a contributing factor in an atraumatic concept. The aim of our study was to observe intracochlear pressure changes due to different opening conditions of an artificial round window membrane. The experiments were performed in an artificial cochlea model. A round window was simulated with a polythene foil and a pressure sensor was placed in the helicotrema area to monitor intraluminal pressure changes. Openings of the artificial round window membrane were performed using different ways. Opening the artificial round window mechanically showed a biphasic behaviour of pressure change. Laser openings showed a unidirectional pressure change. The lowest pressure changes were observed when opening the artificial round window membrane using a diode laser. The highest pressure changes were seen when using a needle. The openings with the CO2 laser showed a negative intracochlear pressure and a loss of fluid. In our model experiments, we could prove that the opening of the artificial round window membrane causes various intracochlear pressure changes.

Radiological control of the floating mass transducer attached to the round window.

The surgical rehabilitation of mixed hearing losses can be performed by coupling the floating mass transducer of the Vibrant Soundbridge to the round window. The quality of coupling the floating mass transducer to the round window is crucial for the audiological outcome. It was the aim of this study to further observe the different patterns of floating mass transducer position at the round window. We compared twenty patients with mixed hearing loss implanted with a floating mass transducer attached to the round window and 24 surgeries between 5/2007 and 6/2010. An evaluation of the chronological observation of the flat panel angiography-controlled position of the floating mass transducer at the round window with relation to the surgical report and the audiological outcome was done. We observed no changes in the mean pre- and postbone conduction thresholds. The floating mass transducer position was variable and could be radiologically classified and correlated with the audiologically outcome. A learning curve was observed from the earlier to later implantations. Postoperative, radiological evaluation of the location and angle of the floating mass transducer by means of flat panel tomography allowed us to classify the floating mass transducer position at the round window into 4 groups.