Implantation of the ossified cochlea: management with the split electrode array

OBJECTIVES/HYPOTHESIS: To describe indications for, the surgical technique required, and the expected functional results of split electrode array cochlear implants. STUDY DESIGN: Retrospective chart review. METHODS: Data collected included etiology of deafness, radiographic findings, pre- and postoperative aided pure tone thresholds, and speech perception testing. Adult speech perception outcomes were measured using the Consonant Nucleus Consonant (CNC) monosyllable words and Hearing in Noise Test (HINT) in quiet/noise (+10 dB). The children were assessed using the Infants and Toddlers Meaningful Auditory Integration Scale. RESULTS: Five patients were implanted with a split electrode array. This included two adults and three children. Both adults had preoperative binaural aided pure tone averages worse than 50 dB and scores of 0% on both HINT quiet and CNC words. The children had undetectable preoperative aided thresholds and scored an average 4/40 on the IT-MAIS. Postimplant, the average threshold gain was 38.5 dB in the adults and 81.5 dB in the children. One adult improved to score 51%/22% on HINT quiet/noise at 6 months and 72%/30% at 12 months. The other adult continued to score 0% on HINT at 12 months but claimed substantial subjective auditory improvement after the first year of device use. The children averaged 28/40 on the IT MAIS at 6 months after implantation. Forty-two of 48 implanted electrodes were functional. CONCLUSIONS: The split electrode array is a useful alternative to traditional cochlear implants in treating deafened patients with cochlear ossification. Patients implanted with the split array show marked improvement in sound and speech perception.     

Measurements of electrode position inside the cochlea for different cochlear implant systems

CONCLUSIONS: This study demonstrates that the exact location of an electrode inside the cochlea needs to be assessed using two complementary measures, namely the length and angle of insertion, both of which are mandatory if one wants to prevent erroneous outcomes. Knowledge of the contact position may become very useful when tuning a cochlear implant processor in a patient with contralateral residual hearing, or in cases of binaural implants. OBJECTIVE: Multichannel cochlear implants restore useful hearing to deaf patients. However, several types of intracochlear electrodes are presently available, each featuring a specific technology or design. The aim of this study was to determine precisely the intracochlear position of the contacts for different electrode arrays. MATERIAL AND METHODS: Electrode array insertions were estimated using special radiographs. A total of 26 cochlear implantations were included in the study: 6 Ineraid; 5 Clarion HiFocus I; 11 Clarion HiFocus II; and 4 Med-El Combi40+. In each case, a measurable reference or marker ring placed close to the round window (within 2 mm) could be identified. Insertion lengths and angles were measured and then plotted on a graphl based on 3D reconstructions. RESULTS: Both Clarion HiFocus I and II electrode arrays were found to be placed close to the inner wall of the cochlea. Ineraid and Med-El Combi40+ electrode arrays were both placed close to the organ of Corti, the Med-El Combi40+ arrays demonstrating the deepest insertions overall. In spite of marked differences in the positions of the contacts, we did not find any correlation with speech perception performance for the different types of implants studied.     

Cochlear implant electrode array misplaced in Hyrtl's fissure

Hyrtl's fissure is a cleft that is present in the developing fetal petrous temporal bone and extends from the area inferior to the round window to the meninges of the posterior fossa. Persistent Hyrtl's fissure, due to incomplete ossification, is considered a rare temporal bone malformation, and is a known cause of perilabyrinthine cerebrospinal fluid fistula.Very few cases are reported as being at risk of complication of cochlear implant surgery. Here we report the case of an 8-year-old boy with misplacement of an electrode array in Hyrtl's fissure. The diagnosis was made postoperatively, since cochlear implant failure was suspected from non-auditory responses. Computed tomography (CT) revealed the extracochlear location of the electrode array. We emphasize the role of presurgical imaging CT and magnetic resonance imaging in detecting temporal bone abnormalities, and we discuss the value of intraoperative auditory nerve response telemetry and postoperative radiological evaluation in diagnosing cochlear implant misplacement.     

A cochlear implant round window electrode array.

This multiple-electrode array for round window cochlear implantation is a robust, reliable system for inserting 20 mm along the scala tympani with a minimum of trauma and can provide for bipolar stimulation.     

The rationale for FLEX (cochlear implant) electrode with varying array lengths

With cochlear implantation (CI) being the standard of care for profoundly deaf cases, more and more patients with low frequency residual hearing are currently b...     

REZ-1人工耳蜗电极植入方法的改进研究

目的 探讨使REZ-1人工耳蜗电极靠近蜗轴的植入方法.方法 22例尸头标本CT扫描测量耳蜗直径后,植入REZ-1人工耳蜗电极,完成植入后回撤1～2个电极环,耳蜗位摄片,测量蜗轴与电极环之间距离是否有所改变.测量60例CT扫描显示一侧中耳、内耳结构正常病例的耳蜗直径.结果 22例标本中3例植入27个电极环,19例植入28个电极环.回撤电极后,与回撤前相比17例标本中第12至第19个电极环与蜗轴的距离减小(配对t检验,P<0.01),该17例标本的耳蜗直径均小于9.50 mm;而耳蜗直径大于9.60 mm的5例标本均没有出现电极环靠近蜗轴的改变.17例电极回撤后靠近蜗轴的标本耳蜗直径为9.11(0.57)mm[中位数(四分位数间距),下同],另外5例标本耳蜗卣径为9.78(0.28)mm,二者差异具有统计学意义(Mann-Whitney秩和检验,P<0.001).60例正常耳蜗直径(x±s)为(9.04±0.45)mm,90%小于9.50 mm.结论 REZ-1人工耳蜗电极植入后回撤电极的植入方法可以使耳蜗直径小于9.50 mm的患者底回内部分电极环靠近蜗轴.术前CT扫描测量耳蜗直径可以为REZ-1人工耳蜗电极选择植入方法提供帮助.     

An improved cochlear implant electrode array for use in experimental studies

Experimental studies play an important role in establishing the safety and efficacy of cochlear implants and they continue to provide insight into a new generation of electrode arrays and stimulation strategies. One drawback has been the limited depth of insertion of an electrode array in experimental animals. We compared the insertion depth and trauma associated with the insertion of Cochlear Ltd's Hybrid-L (HL) array with a standard 8 ring array in cat cochleae. Both arrays were inserted into cadaver cochleae and an X-ray recorded their anatomical location. The implanted cochlea was serially sectioned and photographed at 300?μm intervals for evidence of electrode insertion trauma. Subsequently two cats were chronically implanted with HL arrays and electrically-evoked potentials recorded over a three month period. Mean insertion depth for the HL arrays was 334.8° (SD?=?21°; n?=?4) versus 175.5° (SD?=?6°; n?=?2) for the standard array. This relates to ～10.5?mm and 6?mm respectively. A similar insertion depth was measured in a chronically implanted animal with an HL array. Histology from each cadaver cochleae showed that the electrode array was always located in the scala tympani; there was no evidence of electrode insertion trauma to the basilar membrane, the osseous spiral lamina or the spiral ligament. Finally, evoked potential data from the chronically implanted animals exhibited significantly lower thresholds compared with animals implanted with a standard 8 ring array, with electrical thresholds remaining stable over a three-month observation period. Cochlear Ltd's HL electrode array can be safely inserted ～50% of the length of the cat scala tympani, placing the tip of the array close to the 4?kHz place. This insertion depth is considerably greater than is routinely achieved using a standard 8-ring electrode array (～12?kHz place). The HL array evokes low thresholds that remain stable over three months of implantation. This electrode array has potential application in a broad area of cochlear implant related research.     

Psychophysics of a prototype peri-modiolar cochlear implant electrode array

Psychophysical measurements were performed in three hearing-impaired adult subjects implanted with a CI22 cochlear prosthesis (Cochlear Ltd.) fitted with a developmental peri-modiolar electrode array. The array was manufactured with a curvature approximating that of the inner wall of the scala tympani but, after straightening and insertion, lay on average about half way between the inner and outer walls of the scala. All subjects were tested with bipolar stimulation; two were also tested with monopolar, employing the most basal electrode as the return. Maximum comfortable level and threshold reduced with decreasing distance of electrode from the modiolus, whereas dynamic range increased. The linearity of the loudness growth function did not vary significantly with electrode position but the function was more non-linear for lower maximum comfortable levels. Current level discrimination, normalized with respect to dynamic range, improved with decreasing distance of electrode from the modiolus in two subjects. Pitch varied regularly with insertion depth of the stimulated electrode for bipolar stimulation in two subjects and also for monopolar stimulation in one subject. Electrode discrimination was enhanced by closeness to the modiolus. Whereas the forward masking patterns for bipolar stimulation of electrodes close to the modiolus had a sharp double-peaked structure, those for monopolar stimulation were flatter and had a single peak.     

Challenging aspects of contemporary cochlear implant electrode array design

ObjectiveA design comparison of current perimodiolar and lateral wall electrode arrays of the cochlear implant (CI) is provided. The focus is on functional features such as acoustic frequency coverage and tonotopic mapping, battery consumption and dynamic range. A traumacity of their insertion is also evaluated.MethodsReview of up-to-date literature.ResultsPerimodiolar electrode arrays are positioned in the basal turn of the cochlea near the modiolus. They are designed to initiate the action potential in the proximity to the neural soma located in spiral ganglion. On the other hand, lateral wall electrode arrays can be inserted deeper inside the cochlea, as they are located along the lateral wall and such insertion trajectory is less traumatic. This class of arrays targets primarily surviving neural peripheral processes. Due to their larger insertion depth, lateral wall arrays can deliver lower acoustic frequencies in manner better corresponding to cochlear tonotopicity. In fact, spiral ganglion sections containing auditory nerve fibres tuned to low acoustic frequencies are located deeper than 1 and half turn inside the cochlea. For this reason, a significant frequency mismatch might be occurring for apical electrodes in perimodiolar arrays, detrimental to speech perception. Tonal languages such as Mandarin might be therefore better treated with lateral wall arrays. On the other hand, closer proximity to target tissue results in lower psychophysical threshold levels for perimodiolar arrays. However, the maximal comfort level is also lower, paradoxically resulting in narrower dynamic range than that of lateral wall arrays. Battery consumption is comparable for both types of arrays.ConclusionsLateral wall arrays are less likely to cause trauma to cochlear structures. As the current trend in cochlear implantation is the maximal protection of residual acoustic hearing, the lateral wall arrays seem more suitable for hearing preservation CI surgeries. Future development could focus on combining the advantages of both types: perimodiolar location in the basal turn extended to lateral wall location for higher turn locations.     

Evaluation of streamlined programming procedures for the Nucleus cochlear implant with the Contour electrode array

OBJECTIVE: The objective of this study was to evaluate streamlined programming procedures for the Nucleus cochlear implant system with the Contour electrode array. DESIGN: Phase 1 involved an examination of the clinical MAPs for the first 103 recipients implanted with the Contour electrode array in the Melbourne Cochlear Implant Clinic, to examine the ability to predict the entire MAP based on a smaller number of clinically determined T- and/or C-levels. In phase 2, a subset of the streamlined procedures was selected and clinically evaluated, using speech perception and subjective preference measures. In the first study, the clinical MAP was compared with a MAP based on interpolating across three behavioral T-levels and three behavioral C-levels in a group of newly implanted subjects. The second study investigated the use of a single interpolated profile as the basis to creating the entire MAP. Initial evaluation compared the clinical MAP with two streamlined MAPs, one in which the C-level profile was derived from interpolation across a subset of T-levels and one in which the T-level profile was derived from interpolation across a subset of C-levels. In this case, the interpolated profile was based on five behavioral measures. Subsequently, the use of either three or a single T-level measure as the basis for the interpolated T-level profile was evaluated. Eighteen subjects, who were experienced with the clinical MAP before enrollment in the study, participated in the initial evaluation. The subjects were selected to include a group whose RMS deviation from clinical MAP levels, as determined in Phase 1, was greater than that of the wider population. RESULTS: The Phase 1 analysis showed that as expected, larger differences were observed between the clinical and derived MAP levels as interpolation was applied across fewer measured electrodes and that the use of a single interpolated profile to create the entire MAP resulted in the greatest deviation. No significant group mean difference was found in speech perception scores for newly implanted subjects when mapped with the clinical versus the streamlined MAP based on three behavioral T- and three behavioral C-level measures. For some individual subjects, scores were higher with the streamlined MAP. Subjective reports from the comparative performance questionnaire were consistent with these findings. No significant group mean difference in speech perception scores was found in comparing the clinical MAP with the streamlined MAPs based on a single interpolated T- or C-level profile created from five behavioral measures. Individual effects were observed; however, there was no consistent finding across subjects. The use of three rather than five behavioral T-level measures in the procedure did not result in significantly lower group mean scores; however, significantly poorer scores were obtained for three of the 10 individual subjects. The use of a MAP based on a single behavioral measure did result in poorer speech perception scores when compared with the MAP based on five behavioral T-level measures. These findings were consistent with subjective results from the performance questionnaires administered to determine preference for program across a range of listening situations. CONCLUSIONS: Two streamlined programming procedures are recommended for use in the clinical setting: (1) interpolating across three measured T-levels and three measured C-levels and (2) interpolating across five measured T- or C-levels and using the interpolated profile for fitting of the alternative profile.     

Cochlear implant insertion forces in microdissected human cochlea to evaluate a prototype array

Cochlear implant array insertion forces are potentially related to cochlear trauma. We compared these forces between a standard (Digisonic SP; Neurelec, Vallauris, France) and an array prototype (Neurelec) with a smaller diameter. The arrays were inserted by a mechatronic tool in 23 dissected human cochlea specimens exposing the basilar membrane. The array progression under the basilar membrane was filmed together with dynamic force measurements. Insertion force profiles and depth of insertion were compared. The recordings showed lower insertion forces beyond 270° of insertion and deeper insertions with the thin prototype array. This will potentially allow larger cochlear coverage with less trauma.     

Visualization of cochlear implant electrode movements in the cochlea by using x-ray microscopy

BACKGROUND: The movements of the electrode cable of a cochlear implant inside the cochlea during the insertion procedure generally are invisible, even in temporal bone experiments. Yet, the development of new designs of electrodes, their positioning near to the modiolus etc. requires an exact knowledge on the dynamic behaviour of the electrodes inside the cochlea. The exclusive method for looking through the undamaged cochlea walls is by x-ray technique. METHODS: A specific x-ray tube with a focal spot size of barely 5 microns allows useful direct magnifications of more than 20-30 times. We performed temporal bone experiments with this tube and studied the behaviour of conventional and perimodiolar electrode cables of a MedEl-Cl during the insertion procedure under fluoroscopic viewing. RESULTS: The high resolution imaging revealed the influence of stiffness of the electrode cable on the insertion depth of a conventional electrode. If the angle of the direction of insertion was too steep, the resulting kinking of the cable at the medial wall of the basal turn was instantly visible. The direct visualisation of the movements of the cable was useful in optimizing the design and stiffness of various prototypes of perimodiolar electrodes for a deep insertion. CONCLUSIONS: The dynamic examination technique disclosed that the stiffness of actual electrode cables is not optimally adapted to the form of the cochlear cavity for deep insertion. The non-destructive visualisation technique will facilitate the development of advanced electrode design, especially for various concepts of perimodiolar electrodes.     

Review on cochlear implant electrode array tip fold-over and scalar deviation

ObjectiveDetermine the occurrence rate of cochlear implant (CI) electrode tip fold-over and electrode scalar deviation as reported in patient cases with different commercial electrode types.Data-sourcesPubMed search for identifying peer-reviewed articles published till 2018 on CI electrode tip fold-over and scalar deviation. Key-words for searching were “Cochlear electrode tip fold-over”, “Cochlear electrode scalar position” and “Cochlear electrode scalar location”.Articles-selectionOnly if electrode related issues were investigated in patient cases. 38 articles met the inclusion-criteria.Results13 articles on electrode tip fold-over issue covering 3177 implanted ears, out of which 50 ears were identified with electrode tip fold-over with an occurrence rate of 1.57%. Out of 50 ears, 43 were implanted with pre-curved electrodes and the remaining 7 with lateral-wall electrodes. One article reported on both tip fold-over and scalar deviation. 26 articles reported on the electrode scalar deviation covering an overall number of 2046 ears out of which, 458 were identified with electrode scalar deviation at a rate of 22.38%. After removing the studies that did not report on the number of electrodes per electrode type, it was 1324 ears implanted with pre-curved electrode and 507 ears with lateral-wall electrode. Out of 1324 pre-curved electrode implanted ears, 424 were reported with scalar deviation making an occurrence rate of 32%. Out of 507 lateral-wall electrode implanted ears, 43 were associated with scalar deviation at an occurrence rate of 6.7%.ConclusionThis literature review revealing the fact of higher rate of electrode insertion trauma associated with pre-curved electrode type irrespective of CI brand is one step closer to obsolete it from the clinical practice in the interest of patient's cochlear health.     

Substance distribution in a cochlea model using different pump rates for cochlear implant drug delivery electrode prototypes

Several studies using animals have shown the protective effects of neurotrophic factors (NF) on spiral ganglion cells (SGC). This is of particular importance since the number of SGCs is considered to be among the factors defining the efficacy of cochlear implants. A device for local inner ear treatment is therefore of great interest. As described previously, we modified a Contour(TM) cochlear implant electrode, to examine the inbuilt canal to be used for fluid release [Paasche, G., Gibson, P., Averbeck, T., Becker, H., Lenarz, T., St?ver, T., 2003. Technical report: modification of a cochlear implant electrode for drug delivery to the inner ear. Otol. Neurotol. 24, 222-227]. In the present study, three different electrode prototypes with openings of the delivery channel at various locations along the electrode array were examined to determine distribution of dye in a cochlea model over time. We compared dye delivery with: (a) release of the dye at the tip, (b) release of the dye at the tip and the side of the electrode, and (c) release of the dye only at the side of the electrode (6 mm from the tip). A mechanical pump was used to drive the system at pump rates of 100, 10, and 1 microl/h. Dye concentration changes along the length of the whole cochlea were investigated. Mean values for all experimental conditions show that the distribution along the array is fastest with two outlets whereas the distribution via a single outlet at the side of the electrode array is not considered to be sufficient. The established experimental setup provides the possibility of investigating prototypes of a fluid based drug delivery system for the treatment of inner ear pathologies in combination with electrical stimulation.     

Natural course of residual hearing preservation with a slim,modiolar cochlear implant electrode array

PurposeUnderstanding residual hearing preservation and its natural course following cochlear implantation is important for developing rehabilitation strategies for hearing loss. However, non-uniform evaluation criteria and varying surgical skills pose challenges in fair comparison of the effect of different electrodes on residual hearing preservation. We compared the effect of a slim modiolar electrode (SME) and a slim straight electrode (SSE), implanted by a single surgeon, on progression of residual hearing using different parameters, based on cross-sectional and longitudinal audiological analyses.MethodsPatients with preoperative low-frequency pure-tone average (LFPTA) ≤85 dB at 250 and 500 Hz and who underwent minimally traumatic surgical techniques were included. The progression of residual hearing using threshold shifts, hearing preservation rate according to the HEARRING classification, and maintenance of functional low-frequency hearing potentially qualifying for a hybrid stimulation was analyzed up to five time points throughout the 1-year follow-up period.ResultsThreshold shifts and hearing preservation rates according to the HEARRING classification of the electrodes were comparable from 3 months through 12 months postoperatively. Maintenance of functional low-frequency hearing, required for the usage of a hybrid stimulation, was similar for both electrodes. A substantial proportion of implantees with SME use a hybrid stimulation, resulting in long-term use. However, a difference in the pattern of postoperative residual hearing preservation between the two electrodes is possible, probably due to differences in their physical characteristics and location. Specifically, correlation analysis exhibited that significantly less tight modiolar proximity negatively affect the residual hearing preservation, albeit only at 3 months postoperatively, among patients with the SME.ConclusionCollectively, both SME and SSE implantation showed favorable residual hearing preservation. Our findings further refine the recently proposed hearing preservation with the SME and suggest that the physical characteristics and location of electrodes, in terms of electrode-to-modiolus distance, could affect loss of acoustic hearing in various ways.     

直电极与弯电极序列人工耳蜗植入深度的比较

目的测量比较Nucleus CI 24M直电极序列和CI24 Contour弯电极序列两种型号植入体的电极植入深度。方法对41例CI 24M和8例CI 24 Contour植入者,术后拍摄耳蜗位X线平片。应用图像处理技术,比照耳蜗螺旋模板,建立电极序列的极坐标图形,测量第22号电极与耳蜗开窗处的极坐标角度,两者之差代表了电极序列的植入深度。以t检验比较两种型号植入体的植入深度状况。结果 无内耳畸形、手术条件相当的情况下,CI 24 Contour植入体的平均插入角度为413°,CI 24M植入体的平均插入角度为316°,P=0.0001。结论CI 24 Contour植入体的植入深度明显深于CI 24M。前者更有利于医师进行植入。     

Cochleostomy and facial recess packing alter cochlear implant electrode location in a human cochlea model

Purpose

Determine the effect of cochleostomy and facial recess packing on cochlear implant electrode distance from the modiolus.