Uncovering Vulnerable Phases in Cochlear Implant Electrode Array Insertion: Insights from an In Vitro Model.

OBJECTIVES: The aim of this study is to improve our understanding of the mechanics involved in the insertion of lateral wall cochlear implant electrode arrays. DESIGN: A series of 30 insertion experiments were conducted by three experienced surgeons. The experiments were carried out in a previously validated artificial temporal bone model according to established soft surgery guidelines. The use of an in vitro setup enabled us to comprehensively evaluate relevant parameters, such as insertion force, intracochlear pressure, and exact electrode array position in a controlled and repeatable environment. RESULTS: Our findings reveal that strong intracochlear pressure transients are more frequently caused during the second half of the insertion, and that regrasping the electrode array is a significant factor in this phenomenon. For choosing an optimal insertion speed, we show that it is crucial to balance slow movement to limit intracochlear stress with short duration to limit tremor-induced pressure spikes, challenging the common assumption that a slower insertion is inherently better. Furthermore, we found that intracochlear stress is affected by the order of execution of postinsertion steps, namely sealing the round window and posterior tympanotomy with autologous tissue and routing of the excess cable into the mastoid cavity. Finally, surgeons' subjective estimates of physical parameters such as speed, smoothness, and resistance did not correlate with objectively assessed measures, highlighting that a thorough understanding of intracochlear mechanics is essential for an atraumatic implantation. CONCLUSION: The results presented in this article allow us to formulate evidence-based surgical recommendations that may ultimately help to improve surgical outcome and hearing preservation in cochlear implant patients.

A Sleeve-Based, Micromotion Avoiding, Retractable and Tear-Opening (SMART) Insertion Tool for Cochlear Implantation.

OBJECTIVE: In conventional cochlear implantation, the insertion of the electrode array is strongly affected by the local anatomy and human kinematics. Herein, we present a concept for an insertion tool that allows to optimize the insertion trajectory beyond anatomical constraints and stabilizes the electrode array in manual implantation. A novel sleeve-based design allows the instrument to be compliant and potentially protective to intracochlear structures, while a tear-open mechanism allows it to be removed after insertion by simply retracting the tool. METHODS: Conventional and tool-guided manual insertions were performed by expert cochlear implant surgeons in an analog temporal bone model that allows to simultaneously record intracochlear pressure, insertion forces and electrode array deformation. RESULTS: Comparison between conventional and tool-guided insertions demonstrate a substantial reduction of maximum insertion forces, force variations, transverse intracochlear electrode array movement, and pressure transients. CONCLUSION: The presented tool can be utilized in manual cochlear implantation and significantly improves key metrics associated with intracochlear trauma. SIGNIFICANCE: The instrument may ultimately help improve hearing outcomes in cochlear implantation. The versatile design may be used in both manual cochlear implantation and motorized and robotic insertion, as well as image-guided surgery.

Cochlear base length as predictor for angular insertion depth in incomplete partition type 2 malformations.

INTRODUCTION: The preoperative determination of suitable electrode array lengths for cochlear implantation in inner ear malformations is a matter of debate. The choice is usually based on individual experience and the use of intraoperative probe electrodes. The purpose of this case series was to evaluate the applicability and precision of an angular insertion depth (AID) prediction method, based on a single measurement of the cochlear base length (CBL). METHODS: We retrospectively measured the CBL in preoperative computed tomography (CT) images in 10 ears (8 patients) with incomplete partition type 2 malformation. With the known electrode length (linear insertion depth, LID) the AID at full insertion was retrospectively predicted for each ear with a heuristic equation derived from non-malformed cochleae. Using the intra- or post-implantation cone beam CT images, the actual AID was assessed and compared. The deviations of the predicted from the actual insertion angles were quantified (clinical prediction error) to assess the precision of this single-measure estimation. RESULTS: Electrode arrays with 15 mm (n = 3), 19 mm (n = 2), 24 mm (n = 3), and 26 mm (n = 2) length were implanted. Postoperative AIDs ranged from 211° to 625°. Clinical AID prediction errors from -64° to 62° were observed with a mean of 0° (SD of 44°). In two ears with partial insertion of the electrode, the predicted AID was overestimated. The probe electrode was intraoperatively used in 9/10 cases. CONCLUSION: The analyzed method provides good predictions of the AID based on LID and CBL. It does not account for incomplete insertions, which lead to an overestimation of the AID. The probe electrode is useful and well established in clinical practice. The investigated method could be used for patient-specific electrode length selection in future patients.

Bilateral congenital deafness: What investigations should be performed?

BACKGROUND: The introduction of newborn hearing screening has led to earlier identification of children with congenital sensorineural hearing loss (SNHL). Aetiological clarification offers several benefits. There is currently a lack of agreement on which examinations should be recommended. OBJECTIVE: Descriptive review of the literature reporting investigations performed to establish the aetiology of congenital SNHL and comparison of the management policy in Swiss referral centres. METHODS: PubMed Search from 1985 to March 2016 with specific search terms; study selection according to inclusion/exclusion criteria; narrative analysis by use of defined criteria and question-naire. RESULTS: Ninety-two studies were finally included in this review. Forty studies investigated more than a single aetiology. Overall frequencies of aetiological parameters investigated were: genetic (47 studies), radiological (35), ophthalmic (35), serological (32), cardiac (25), renal (14), endocrine (12), neurological (8). Most of the studies were retrospective and various limitations such as poor population description, incomplete data or deficiencies in methodological quality were frequently detected. The variability detected in the investigative approach chosen by Swiss referral centres reflects the heterogeneous data seen in the literature. CONCLUSIONS: The evidence in the literature regarding an appro-priate evaluation is mostly of low quality and difficult to assess owing to high heterogeneity. Nevertheless, imaging, genetic testing, neuropaediatric and ophthalmological evaluations, electrocardiograms and cytomegalovirus analysis have been identified as examinations to be included in the assessment of children with congenital SNHL. There is a need for international consensus on the various issues of such an evaluation, such as choice of investigations and diagnostic criteria.

Significant Artifact Reduction at 1.5T and 3T MRI by the Use of a Cochlear Implant with Removable Magnet: An Experimental Human Cadaver Study.

OBJECTIVE: Cochlear implants (CIs) are standard treatment for postlingually deafened individuals and prelingually deafened children. This human cadaver study evaluated diagnostic usefulness, image quality and artifacts in 1.5T and 3T magnetic resonance (MR) brain scans after CI with a removable magnet. METHODS: Three criteria (diagnostic usefulness, image quality, artifacts) were assessed at 1.5T and 3T in five cadaver heads with CI. The brain magnetic resonance scans were performed with and without the magnet in situ. The criteria were analyzed by two blinded neuroradiologists, with focus on image distortion and limitation of the diagnostic value of the acquired MR images. RESULTS: MR images with the magnet in situ were all compromised by artifacts caused by the CI. After removal of the magnet, MR scans showed an unequivocal artifact reduction with significant improvement of the image quality and diagnostic usefulness, both at 1.5T and 3T. Visibility of the brain stem, cerebellopontine angle, and parieto-occipital lobe ipsilateral to the CI increased significantly after magnet removal. CONCLUSIONS: The results indicate the possible advantages for 1.5T and 3T MR scanning of the brain in CI carriers with removable magnets. Our findings support use of CIs with removable magnets, especially in patients with chronic intracranial pathologies.

Retrograde cochlear implantation in postmeningitic basal turn ossification.

OBJECTIVES/HYPOTHESIS: Postmeningitic basal turn ossification is a challenge for successful cochlear implantation despite the availability of sophisticated implants and advanced drill-out procedures. A less complex concept consisting of a cochleostomy near the apex with retrograde array insertion is evaluated clinically and experimentally with emphasis on imaging of intracochlear array morphology. STUDY DESIGN: Retrospective case-control study. METHODS: Outcome, hearing performance, and radiological findings including three-dimensional (3D) reconstructions were assessed in the long term in eight retrograde implanted ears of seven postmeningitic deaf patients and compared to an etiology- and device-matched control group of 17 basal turn implanted ears of 14 patients. Experimental insertions into three autopsy-derived human temporal bones were evaluated using high-resolution microtomography, 3D reconstruction, and histology. RESULTS: No complications occurred. At the long-term follow-up, the average monosyllabic word test scores were 41% for the study group and 67% for the control group (P = .03). Radiological follow-up revealed insertion sites into either the apical or middle turn and frequent intracochlear array direction changes (n = 5). Experimental implantations in temporal bones resulted in folding-free, retrograde, middle turn insertions (n = 3). CONCLUSIONS: The retrograde cochlear implantation is a safe and efficient alternative approach in basal turn ossification. Despite a high occurrence of intracochlear array direction changes, open set speech discrimination was achieved in all patients. Postoperative computed tomography is recommended for fitting the speech processor according to intracochlear array positions. The experimental insertion in temporal bones helped to optimize the approach.

In-the-canal versus behind-the-ear microphones improve spatial discrimination on the side of the head in bilateral cochlear implant users.

OBJECTIVE: To test whether in-the-canal (ITC) microphones have an impact on spatial discrimination and speech perception by taking advantage of auricular cues. STUDY DESIGN: Experimental clinical study. SETTING: Audiologic laboratory in a tertiary referral center. PATIENTS: Seven bilateral adult cochlear implant (CI) users were selected from the institution's database. INTERVENTION: The adaptive German Oldenburg sentence test and minimum audible angle measurements were performed binaurally with experimental ITC and behind-the-ear (BTE) microphones. MAIN OUTCOME MEASURES: Spatial discrimination and speech perception scores assessed for each microphone position. RESULTS: Spatial discrimination on the side of the head was superior using ITC compared with BTE microphone positions; the differences on the side of the first CI were statistically significant (mean minimum audible angle ± standard deviation, 28.4 ± 7.61 degrees versus 34.1 ± 14.4 degrees; p = 0.031). Speech perception scores with ITC versus BTE microphone positions also were improved, although the differences were not statistically significant. CONCLUSION: ITC microphones could help to improve CI performance in the future.

A reservoir of Moraxella catarrhalis in human pharyngeal lymphoid tissue.

BACKGROUND: Early exposure of infants and long-term immunity suggest that colonization with Moraxella catarrhalis is more frequent than is determined by routine culture. We characterized a reservoir of M. catarrhalis in pharyngeal lymphoid tissue. METHODS: Tissue from 40 patients (median age, 7.1 years) undergoing elective tonsillectomy and/or adenoidectomy was analyzed for the presence of M. catarrhalis by culture, real-time DNA and RNA polymerase chain reaction (PCR), immunohistochemical analysis (IHC), and fluorescent in situ hybridization (FISH). Histologic sections were double stained for M. catarrhalis and immune cell markers, to characterize the tissue distribution of the organism. Intracellular bacteria were identified using confocal laser scanning microscopy (CLSM). RESULTS: Twenty-nine (91%) of 32 adenoids and 17 (85%) of 20 tonsils were colonized with M. catarrhalis. Detection rates for culture, DNA PCR, RNA PCR, IHC, and FISH were 7 (13%) of 52, 10 (19%) of 52, 21 (41%) of 51, 30 (61%) of 49, and 42 (88%) of 48, respectively (P<.001). Histologic analysis identified M. catarrhalis in crypts, intraepithelially, subepithelially, and (using CLSM) intracellularly. M. catarrhalis colocalized with macrophages and B cells in lymphoid follicles. CONCLUSIONS: Colonization by M. catarrhalis is more frequent than is determined by surface culture, because the organism resides both within and beneath the epithelium and invades host cells.

Comparison of musical activities of cochlear implant users with different speech-coding strategies.

Speech coding might have an impact on music perception of cochlear implant users. This questionnaire study compares the musical activities and perception of postlingually deafened cochlear implant users with three different coding strategies (CIS, ACE, SPEAK) using the Munich Music Questionnaire. Overall, the self-reported perception of music of CIS, SPEAK, and ACE users did not differ by very much.

Minimum audible angle, just noticeable interaural differences and speech intelligibility with bilateral cochlear implants using clinical speech processors.

Sound localization and speech intelligibility were assessed in 5 patients implanted bilaterally with Medel C40+ or Medel C40 cochlear implant (CI) systems. The minimum audible angle (MAA) around the head in the horizontal plane was assessed in patients with bilateral CI using white noise bursts of 1000 ms duration presented from a loudspeaker mounted on a rotating boom and compared with the MAA of age-matched normal hearing controls. Spatial discrimination was found to be good in front and in the back of the head with near-normal MAA values (patients: 3-8 degrees , controls: 1-4 degrees ). In contrast, poor performance on the sides was found (patients: 30 to over 45 degrees , controls 7-10 degrees ). Bilateral CI significantly improved spatial discrimination in front for all patients, when compared with the use of either CI alone. Just noticeable differences (JNDs) in interaural intensity and time were assessed using white noise bursts (1000 ms duration; 50 ms linear ramp). In addition, interaural time JNDs were assessed using click trains (800 ms duration, 40 mus clicks, 50 Hz) and noise bursts in which either only the envelope or only the fine structure was shifted in time. In comparison with normal hearing controls, patients with bilateral CI showed near-normal interaural intensity JNDs but substantially poorer interaural time JNDs depending on the type of stimulus. In contrast to envelope onset/offset cues, interaural fine structure time differences were not perceived by the patients using CI systems employing the continuous interleaved sampling strategy without synchronization between their pulse stimulation times. Speech intelligibility in quiet and CCITT noise from the side (+/-90 degrees ) was assessed using the German HSM sentence test and was significantly better when using bilateral CI in comparison with either unilateral CI, mainly due to a head shadow effect. These favorable results are in agreement with the patients' subjective experiences assessed with a questionnaire and support the use of bilateral CI.

Scuba diving with cochlear implants.

We report on a patient with bilateral cochlear implants (a Med-El Combi40 and a Med-El Combi40+), as well as considerable experience in scuba diving with both of his implants. After having been exposed to 68 and 89 dives, respectively, in depths of up to 43 m, both cochlear implants are in working order and the patient continues to receive excellent speech recognition scores with both cochlear implant systems. The presented data show that scuba diving after cochlear implantation is possible over a considerable number of dives without any major negative impact on the implants.

Intra- and intersubject comparison of cochlear implant systems using the Esprit and the Tempo+ behind-the-ear speech processor.

A patient with bilateral profound deafness was implanted with a Nucleus CI24M cochlear implant (CI) and used an Esprit behind-the-ear (BTE) speech processor. Thirteen months later, the implant had to be removed because of a cholesteatoma. As the same electrode could not be reinserted, a Medel combi40s CI was implanted in the same ear, and the patient used a Tempo+ BTE processor. After 1 year of use of the Combi40s/Tempo+ system, speech recognition was better and was rated better subjectively than with the CI24M/Esprit system. Speech recognition and subjective ratings were also assessed for two matched groups of nine CI users each, using either an Esprit or a Tempo+ processor. On average, speech recognition scores were higher for the group of Tempo+ users, but the difference was not statistically significant. Users of the Esprit processors rated their device higher in terms of cosmetic appearance and comfort of wearing.

Changes of voice and articulation in children with cochlear implants.

OBJECTIVE: The different speech sounds are formed by the primary voice signal and by the shape of the articulation tract. With this mechanism, specific overtones, the formants, are generated for each vowel. The objective of this study was to investigate the fundamental frequency (F0) of the voice signal and the first three formants (F1-F3) as a parameter of the articulation in prelingually deafened children at different timepoints after cochlear implantation (CI) compared with children with normal speech development. METHODS: Using the Kay CSL 4300B, the fundamental frequency and the formants F1-F3 of the Swiss-German vowel /a/ were investigated at different timepoints after CI in 20 prelingually deafened children aged 3.8-10.2 years by means of spectrographic and linear predictive coding (LPC) analysis. RESULTS: Children who had been operated before their fourth birthday showed no significant deviation in their fundamental frequency from age- and sex-matched peers, whereas a significant difference was documented in children who were older at the time of implantation. The first formant was very stable in every child and showed only discrete deviations from the normal range. The second and third formants, however, developed a broader scatter, but there was no systematic deviation of these formants to higher or lower values. The F1:F2 ratio was normal in children who were implanted at the age of up to 4 years and more centralized in children who were older at the time of implantation, as is known from the hearing impaired. CONCLUSIONS: Our results indicate that prelingually deaf children who receive a cochlear implant before their fourth birthday attain a better acoustic control over their speech, normalizing their fundamental frequencies and improving their articulatory skills.