MRI-induced artifact by a cochlear implant with a novel magnet system: an experimental cadaver study.

PURPOSES: To primarily evaluate MRI-induced effects for Ultra 3D cochlear implantation in human cadavers in terms of artifact generation and MR image quality. METHODS: Three human cadaveric heads were submitted to imaging after unilateral and bilateral cochlear implantation. The 1.5 T MR examination protocol was chosen in accordance with our institutional protocol for the assessment of brain pathology. The maximal signal void size was measured according to each sequence and plane. Two experienced neuro-radiologists and one experienced otoneurosurgeon independently evaluated the MR image quality findings. A 4-point scale was used to describe the diagnostic usefulness of 14 brain structures. RESULTS: Shape and size of the artifacts were found to be highly related to MRI sequences and acquisition planes. MRI sequences and processing algorithms affected the ability to assess anatomical visibility. Image quality appeared either high or assessable for diagnostic purposes in 9 out of 14 of the ipsilateral structures, in at least one plane. Anatomical structures contralateral to the cochlear implant were highly visible in all conditions. Artifact intrusion clearly improved after application of metal artifact-reduction techniques. In the case of bilateral cochlear implant, a mutual interaction between the two implant magnets produced an additional artifact. CONCLUSIONS: We performed the first cadaver study aimed at systematically evaluating the MRI-induced artifacts produced by a cochlear implant with a novel four bar magnet system. Specific brain structures can be assessable for diagnostic purposes under 1.5 T MRI, with the cochlear implant magnet in place.

Evaluation of a new slim lateral wall electrode for cochlear implantation: an imaging study in human temporal bones.

PURPOSE: To evaluate the insertion characteristics and trauma of a new slim lateral wall electrode (SlimJ) in human temporal bones (TB). METHODS: Pre- and postoperative assessment was performed using cone beam computed tomography (CBCT) and image fusion in 11 human TB. The position of the array in each cochlea was analyzed and described using a vertical scaling factor, calculated by dividing the distance of the scala tympani floor to the centre of the electrode by the duct height. Insertion trauma was scaled according to the presumed localization of the basilar membrane, which was modeled from histologic sections of 20 TBs. The insertion trauma was described by the adaptation of the Eshragi trauma grading. RESULTS: A full electrode insertion, via the round window, was achieved in all TBs. Surgical handling was good, with a favorable compromise between high flexibility but sufficient stiffness to facilitate smooth insertions. The median angular insertion depth was 368° (range 330°-430°). Scala tympani placement was achieved in ten out of eleven TBs; in one TB a scala translocation was observed, occurring at approximately 180°. CONCLUSIONS: The SlimJ showed atraumatic insertion characteristics. The CBCT fusion technique provides an accurate and reliable assessment of the electrode position and allows for grading insertion trauma without histology. The SlimJ true potential for structure and hearing preservation needs to be further assessed in vivo.

Multicenter surgical experience evaluation on the Mid-Scala electrode and insertion tools.

The HiFocus Mid-Scala electrode is intended to improve hearing for individuals with severe-to-profound hearing loss by providing extended electrical coverage of the cochlea while minimizing trauma related to insertion. The electrode is appropriate for use with a wide range of surgical techniques, including either a cochleostomy or round window insertion, and the use of either a free-hand or tool-assisted approach. The objective of this survey was to evaluate how the HiFocus Mid-Scala electrode and insertion tools was used across a population of cochlear implant recipients of differing ages, audiologic profiles, and anatomical characteristics. The intent was to understand the type and frequency of surgical techniques applicable with the electrode, and to provide guidelines for clinical practice. Two questionnaires were completed by surgeons at implant centres located in the United States, Europe, and Asia. Before any surgeries were conducted, surgeons completed a questionnaire that assessed their overall cochlear implant surgical practice and preferences. Following each HiFocus Mid-Scala electrode insertion, surgeons completed a questionnaire that summarized their experience during that surgical procedure. Questionnaires were completed by 32 surgeons from 16 centres for a total of 143 surgeries (112 adults, 31 children). Most surgeons (62 %) preferred to insert the electrode via the round window or an extended round window compared with a cochleostomy (16 %), whereas the remaining 22 % indicated that they made an insertion choice based on presenting anatomy. Sixty-nine percent preferred a free-hand approach over using insertion tools. In 32 procedures, surgeons elected to deviate from an intended round window insertion to either an extended round window or cochleostomy approach.

Insertion characteristics and placement of the Mid-Scala electrode array in human temporal bones using detailed cone beam computed tomography.

The aim of this study was to evaluate the insertion results and placement of the new Advanced Bionics HiFocus Mid-Scala (HFms) electrode array, inserted through the round window membrane, in eight fresh human temporal bones using cone beam computed tomography (CBCT). Pre- and post-insertion CBCT scans were registered to create a 3D reconstruction of the cochlea with the array inserted. With an image fusion technique both the bony edges of the cochlea and the electrode array in situ could accurately be determined, thus enabling to identify the exact position of the electrode array within the scala tympani. Vertical and horizontal scalar location was measured at four points along the cochlea base at an angular insertion depth of 90°, 180° and 270° and at electrode 16, the most basal electrode. Smooth insertion through the round window membrane was possible in all temporal bones. The imaging results showed that there were no dislocations from the scala tympani into the scala vestibule. The HFms electrode was positioned in the middle of the scala along the whole electrode array in three out of the eight bones and in 62 % of the individual locations measured along the base of the cochlea. In only one cochlea a close proximity of the electrode with the basilar membrane was observed, indicating possible contact with the basilar membrane. The results and assessments presented in this study appear to be highly accurate. Although a further validation including histopathology is needed, the image fusion technique described in this study represents currently the most accurate method for intracochlear electrode assessment obtainable with CBCT.

Comparison of a Mid Scala and a Perimodiolar Electrode in Adults: Performance, Impedances, and Psychophysics.

OBJECTIVES: The HiFocus Mid-Scala electrode array (HFms) is designed to sit within the scala tympani without touching either the lateral wall or the modiolus. The aim of this study was to compare the HFms to the Helix perimodiolar electrode array. METHOD: Two groups of recipients with Helix (n = 22 ears) and HFms (n = 29 ears) electrode arrays were retrospectively identified and matched by age at implantation and duration of severe to profound deafness. Most comfortable listening levels (M), impedances, Freiburger Monosyllables in quiet, and Oldenburg sentences in adaptive noise were compared at 3, 6, and 12 months postimplant. RESULTS: Median scores for monosyllables in quiet for the HFms group were significantly better than the Helix group at each test interval (p < 0.05). Speech perception in quiet also significantly improved from 3 to 12 months for both groups (p < 0.001). There was no significant difference between the groups for speech in noise. Impedances were significantly lower for the HFms group at 12 months (p < 0.05) except at the basal end and M levels were generally higher. CONCLUSIONS: The HFms group had better median performance for monosyllables in quiet than the Helix group at each test interval, although performance in noise was similar. For speech in noise, the HFms group appear to reach optimum performance quicker than the Helix group. Impedances were lower in the HFms group across the array, other than at the most basal end, and support our hypothesis that the HFms assumes a more lateral position within the cochlea than the Helix electrode, although our article did not include imaging data.

First Experience With a New Thin Lateral Wall Electrode in Human Temporal Bones.

INTRODUCTION: A modern cochlear implant electrode array design must combine: improved surgical ease of use, structure preservation, particularly important for pediatric application, stable position within the cochlea over time, and a meaningful balance between hearing preservation against addressing sufficient cochlear tissue to support electrical-only hearing. The aim of this study was to investigate a new lateral wall electrode array design from Advanced Bionics on human temporal bones (TBs). METHODS: Ten fresh-frozen TBs were implanted with the SlimJ electrode array via the round window. The electrode array is 23 mm long, with a cross-section varying from 0.25 × 0.55 mm at the most apical contact to 0.6 × 0.8 mm at the proximal marker contact. To assess location of the electrode array, the TBs were postoperatively scanned using cone beam computed tomography, and histology was performed to assess intracochlear trauma (Grades 0-4). RESULTS: All electrode arrays were considered easy to insert. The average insertion depth was 432 degrees measured from the round window with a range from 411 to 450 degrees azimuth. Nine out of 10 electrode arrays were inserted fully (<0.5 mm out of the cochlea), one electrode array was left 1.5 mm out of the cochlea. No translocations were observed in all 10 cochleae, slight touching of the basilar membrane at the distal portion of the array was observed in 50% of the cases. CONCLUSION: The results from the new thin lateral wall electrode array from Advanced Bionics provided consistent scala tympani locations. No translocations were observed and almost all electrode arrays were fully inserted. These results are promising and the new electrode array will be further studied in clinical practice investigating hearing preservation capabilities and speech performance.

Assessment of a Novel 3T MRI Compatible Cochlear Implant Magnet: Torque, Forces, Demagnetization, and Imaging.

HYPOTHESIS: A novel cochlea implant (CI) device magnet providing alignment to the static field of a magnetic resonance imaging (MRI) will lead to reduced torque, longitudinal forces, and demagnetization effects. The image void and distortion will be comparable to those obtained with standard CI magnets. BACKGROUND: MRI investigations of CI users pose several challenges such as magnet dislocation, demagnetization, and may cause pain. The presence of a CI magnet within MRI field causes image distortions and may diminish the diagnostic value of an MRI procedure. Objective of this work is to evaluate magnetic forces and imaging properties of the novel CI magnet within 1.5 and 3T MRI. METHODS: Forces and torque of the novel CI magnet were measured in both 1.5 and 3T MRI and compared with the standard magnet in 1.5T. One cadaver head was implanted with the CI devices containing the novel and standard magnets in different configurations reflecting clinical scenarios and imaging properties were assessed and compared. RESULTS: In particular the torque has been reduced with the novel CI magnet in comparison to the standard one. Both CI magnets have not shown any signs of demagnetization. The image void and distortion was comparable between the two magnets for the main MRI clinical scanning protocols in 1.5T MRI. CONCLUSIONS: The novel CI magnet is safe to use for MRI investigations of CI users in 3T MRI without a need for bandaging and has acceptable level of image artefacts.

A Mid-scala Cochlear Implant Electrode Design Achieves a Stable Post-surgical Position in the Cochlea of Patients Over Time-A Prospective Observational Study.

INTRODUCTION: Cochlear implant (CI) electrode design impacts the clinical performance of patients. Stability and the occurrence of electrode array migration, which is the postoperative movement of the electrode array, were investigated using a mid-scalar electrode array and postoperative image analysis. METHODS: A prospective observational study was conducted. A mid-scalar electrode was surgically placed using a mastoidectomy, followed by a posterior tympanotomy and an extended round-window or cochleostomy insertion. A few days after surgery and 3 months later Cone Beam Computed Tomography (CBCT) was performed. The two different CBCT's were fused, and the differences between the electrode positions in three dimensions were calculated (the migration). A migration greater than 0.5 mm was deemed clinically relevant. RESULTS: Fourteen subjects participated. The mid-scalar electrode migrated in one patient (7%). This did not lead to the extrusion of an electrode contact. The mean migration of every individual electrode contact in all patients was 0.36 mm (95% confidence interval 0.22-0.50 mm), which approximates to the estimated measurement error of the CBCT technique. CONCLUSION: A mid-scalar electrode array achieves a stable position in the cochlea in a small but representative group of patients. The methods applied in this work can be used for providing postoperative feedback for surgeons and for benchmarking electrode designs.

Use of a mid-scala and a lateral wall electrode in children: insertion depth and hearing preservation.

CONCLUSIONS: Atraumatic insertion of the HiFocusTM Mid-Scala (HFMS) electrode via the round window was successfully achieved in seven children. Residual hearing 6 months post-operatively was preserved to within 10 dB HL of the pre-operative audiogram at 500 Hz for six children, indicating minimal initial insertion trauma to the cochlea. OBJECTIVES: The objectives were to document the clinical experience and evaluate differences between HFMS and HiFocusTM 1j (HF1j) by means of insertion depth and hearing preservation results. METHOD: Nineteen children were prospectively recruited and consecutively implanted with the HF1j electrode (n = 12) or the HFMS electrode (n = 7) via the round window. Average median angular insertion depths and the amount of residual hearing preserved at 6 months post-operatively were compared between the two electrode groups. RESULTS: The median angular insertion depth for the HF1j was 439° and for the HFMS 435°. Preservation of residual hearing at 500 Hz was assessed in seven HFMS subjects and 11 HF1j subjects. Based on the Skarzynski formula, three out of seven subjects (42%) in the HFMS group had their residual hearing completely preserved at 500 Hz. In the control group, no subjects had complete hearing preservation and five subjects had a complete loss of residual hearing.

Evaluation of the 'Fitting to Outcomes eXpert' (FOX®) with established cochlear implant users.

OBJECTIVES: To evaluate the possible impact of 'Fitting to Outcomes eXpert (FOX(®))' on cochlear implant (CI) fitting in a clinic with extensive experience of fitting a range of CI systems, as a way to assess whether a software tool such as FOX is able to complement standard clinical procedures. METHODS: Ten adult post-lingually deafened and unilateral long-term users of the Advanced Bionics(TM) CI system (Clarion CII or HiRes 90K(TM)) underwent speech perception assessment with their current clinical program. One cycle 'iteration' of FOX optimization was performed and the program adjusted accordingly. After a month of using both clinical and FOX programs, a second iteration of FOX optimization was performed. Following this, the assessments were repeated without further acclimatization. RESULTS: FOX prescribed programming modifications in all subjects. Soundfield-aided thresholds were significantly lower for FOX than the clinical program. Group speech scores in noise were not significantly different between the two programs but three individual subjects had improved speech scores with the FOX MAP, two had worse speech scores, and five were the same. CONCLUSION: FOX provided a standardized approach to fitting based on outcome measures rather than comfort alone. The results indicated that for this group of well-fitted patients, FOX improved outcomes in some individuals. There were significant changes, both better and worse, in individual speech perception scores but median scores remained unchanged. Soundfield-aided thresholds were significantly improved for the FOX group.

Assessment of 'Fitting to Outcomes Expert' FOX™ with new cochlear implant users in a multi-centre study.

OBJECTIVE: To compare the fitting time requirements and the efficiency in achieving improvements in speech perception during the first 6 months after initial stimulation of computer-assisted fitting with the Fitting to Outcome eXpert' (FOX) and a standard clinical fitting procedure. METHOD: Twenty-seven post-lingually deafened adults, newly implanted recipients of the Advanced Bionics HiRes 90K™ cochlear implant from Germany, the UK, and France took part in a controlled, randomized, clinical study. Speech perception was measured for all participants and fitting times were compared across groups programmed using FOX and conventional programming methods. RESULTS: The fitting time for FOX was significantly reduced at 14 days (P < 0.001) but equivalent over the 6-month period. The groups were not well matched for duration of deafness; therefore, speech perception could not be compared across groups. DISCUSSION: Despite including more objective measures of performance than a standard fitting approach and the adjustment of a greater range of parameters during initial fitting, FOX did not add to the overall fitting time when compared to the conventional approach. FOX significantly reduced the fitting time in the first 2 weeks and by providing a standard fitting protocol, reduced variability across centres. CONCLUSIONS: FOX computer-assisted fitting can be successfully used at switch on, in different clinical environments, reducing fitting time in the first 2 weeks and is efficient at providing a usable program.

Multicentre evaluation of music perception in adult users of Advanced Bionics cochlear implants.

OBJECTIVES: To document musical listening and enjoyment in recipients of Advanced Bionics cochlear implants (CIs) and to compare musical perception in those using early coding strategies with subjects using the newer HiRes and HiRes 120 strategies. METHODS: A questionnaire was completed by 136 adult subjects, including questions on the ability to identify specific musical features. The subjects were in three groups: those using early coding strategies (n = 29), HiRes (n = 59), and HiRes 120 (n = 48), and results were compared with a group of 84 normally hearing (NH) subjects. RESULTS: Of the CI users, 79% reported listening to music. The NH group rated listening frequency and enjoyment higher than the CI users. Thirty-five users reported that they sang and this group had significantly higher overall performance. There were no significant differences in overall perception of specific musical features among the strategy groups, though some individual questions showed significantly higher performance in the HiRes 120 users. DISCUSSION: Users of current CI technology show a high level of musical appreciation, though still significantly less than NH subjects. Frequency of listening and enjoyment were significantly correlated and active participation in musical activities, specifically singing, resulted in significantly higher overall performance scores.