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.

Objective,audiological and quality of life measures with the CI532 slim modiolar electrode

Objectives: To report on electrode array measurements for the Nucleus^® CI532 Slim Modiolar Electrode device including: ECAP thresholds, electrode impedances, and psychophysical comfort levels, as well as speech perception results pre- and post-operatively and standardized evaluations of quality of life.

Methods: Forty-four subjects were implanted with the CI532. Electrically evoked compound action potential (ECAP) thresholds and impedances were measured using automatic Neural Response Telemetry intra-operatively, at activation and at six months post implant. Pre- and post-operative measures of words in quiet and sentences in noise were made in multiple languages. Quality of life was assessed using The Speech Spatial Qualities questionnaire (SSQ) and Glasgow Benefit Inventory (GBI).

Results: Intra-operative ECAP thresholds were recorded successfully from 90% of electrodes tested. ECAP thresholds varied across the array and a post-hoc Dunn’s test showed that median thresholds for electrodes E1–E13 were significantly greater than those for E17–E22 (all P?<?0.001). Impedances increased significantly between surgery and activation. Speech recognition scores for words in quiet and sentences in noise showed a significant improvement for the group at six months, when using the cochlear implant, compared with pre-operative performance (P?<?0.001). There was a significant increase compared to pre-operative ratings for all sections of the SSQ at six months post activation (P?<?0.001). The GBI gave scores significantly above zero for the ‘general’ subscale and total score.

Conclusion: Objective ECAP and impedance measures for this new electrode array were as expected and similar to results reported for other array types. Speech perception and quality of life improved significantly following implantation.

Trial registration: ClinicalTrials.gov identifier: NCT02392403.     

Intra-cochlear electrode tip fold-over

Cochlear implantation has been performed safely for over two decades but still has various minor and major complications. We report two cases of an unusual complication of electrode implantation: tip fold-over of the electrode array within the cochlea. Both cases required undergoing explantation and re-implantation. The frequent use of fine and pre-curved electrodes particularly with the use of an insertion tool necessitates routine postoperative radiological evaluation of the electrode array. Our cases demonstrate the benefit of systematic imaging including the possible use of the Cone Beam CT intraoperatively.     

Nucleus 24CA型人工耳蜗植入后电极阻抗及T/C值变化分析

目的观察Nucleus 24CA型人工耳蜗植入后电极阻抗、行为反应阈值(T-level,T级)及最大舒适级(C-level,C级)的变化规律,分析其内在联系,探讨其对术后调机的指导意义。方法对81例植入Nucleus 24CA型人工耳蜗患儿,分别在术中、术后1、2、6个月进行电极阻抗阈值测试,收集术后对应T、C值,并对其变化规律及相关性进行统计学分析。结果电极阻抗值术中检测最低,术后1月开机最高,此后逐渐减低(P<0.01);自蜗顶至蜗底各通道间电极阻抗值无显著差异(P>0.05)。各电极通道T值、C值随术后时间延长逐渐增高(P<0.05),并与电极阻抗值呈线性相关。结论测定电极阻抗值是评估人工耳蜗刺激电极状态的有效手段;术后2月应同时调试T值及C值,此后则应对C值进行重点调试。     

Large vestibular aqueduct syndrome: Impedance changes over time with different cochlear implant electrode arrays

Abstract

Objectives

The aim of this study was to assess if large vestibular aqueduct syndrome (LVAS), with the increase in perilymphatic pressure, affects impedance changes over time with different types of Cochlear^® implant electrode arrays Contour, Straight, and CI 422. To report speech perception outcomes for these cochlear implant recipients.

Methods

Retrospective case review of impedance levels and categories of auditory performance. Impedance data were collected at switch on, 1 month, 3, 6, 12, and 24 months after cochlear implantation and compared with control (non-LVAS cochlear implant recipient) data for each array type. Forty-seven patients with exclusive LVAS and no other vestibulocochlear abnormalities or other identifiable cause of deafness were eligible for inclusion in the study.

Results

In LVAS patients, there was a significant difference in impedance between the three types of device (P < 0.0001). Time since switch on was associated with a decrease in impedance for all three devices (P < 0.0001). The mean impedance reduced between switch on and 1 month and remained relatively constant thereafter. Sound variation with softening of sounds was seen in four CI 422 (Straight Research Array) recipients due to ongoing fluctuations in electrode compliance.

Discussion

For all three array types, there was no significant difference in the mean impedance between the LVAS patients and controls over the first 12 months. In keeping with previous studies cochlear implant recipients with LVAS hear very well through the cochlear implant.     

Fitting prelingually deafened adult cochlear implant users based on electrode discrimination performance

Objective: This study investigated the hypotheses that (1) prelingually deafened CI users do not have perfect electrode discrimination ability and (2) the deactivation of non-discriminable electrodes can improve auditory performance. Design: Electrode discrimination difference limens were determined for all electrodes of the array. The subjects’ basic map was subsequently compared to an experimental map, which contained only discriminable electrodes, with respect to speech understanding in quiet and in noise, listening effort, spectral ripple discrimination and subjective appreciation. Study Sample: Subjects were six prelingually deafened, late implanted adults using the Nucleus cochlear implant. Results: Electrode discrimination difference limens across all subjects and electrodes ranged from 0.5 to 7.125, with significantly larger limens for basal electrodes. No significant differences were found between the basic map and the experimental map on auditory tests. Subjective appreciation was found to be significantly poorer for the experimental map. Conclusions: Prelingually deafened CI users were unable to discriminate between all adjacent electrodes. There was no difference in auditory performance between the basic and experimental map. Potential factors contributing to the absence of improvement with the experimental map include the reduced number of maxima, incomplete adaptation to the new frequency allocation, and the mainly basal location of deactivated electrodes.     

Identification and revision of a displaced cochlear implant electrode in the internal auditory canal

Abstract

Objective

The aim of the report is to underline the importance of a radiological technique which allows three-dimensional (3D) imaging of the cochlear implant electrode position postoperatively in cases of cochlear malformation, and to show a technique to prevent a repeat of cochlear implant electrode insertion in the internal auditory canal (IAC).

Clinical presentation

This report describes the management of a case of insertion of a cochlear implant electrode into the IAC in a 1.5-year-old patient with an incomplete partition (IP) III cochlear malformation.

Intervention and technique

The commonly used single plain postoperative X-ray is not sufficient to be certain of detecting the incorrect insertion of a cochlear implant electrode in the case of a malformed cochlea. In this case, 3D radiology allowed the incorrect insertion to be detected. The original cochlear implant electrode was temporarily left in place under the assumption that it would block the entrance to the IAC and prevent IAC insertion of the replacement electrode.

Conclusion

Postoperative 3D radiological observation after cochlear implant surgery should be done in cases of malformation. Leaving the original electrode in place can help to prevent a repeat electrode malinsertion.     

人工耳蜗植入术后X线投照位置的探讨

目的:确定耳蜗在颅骨的空间位置,设计最佳耳蜗X线摄片投照角度,用于评价电极位置。方法:测量26例耳蜗植入候选患儿术前CT和32例正常成人中内耳CT片上,耳蜗底周与正中矢状线的夹角;并根据测量的X线投射角度拍摄耳蜗位X线平片。结果:蜗轴中线与正中矢状线的角度为40°到68°,平均52.66°;其中儿童组的平均值为52.52°(s=7.07),成人组的平均值为52.80°(s=5.78),两者间差异无显著性意义(P>0.05)。结论:按所测的X线投射角度拍摄的耳蜗平片,能清晰完整显示电极系列的整体和所有的单个电极,确定电极的插入深度和准确的位置,为频率的匹配定位、语言处理方案的优化提供帮助。     

Relationship between intracochlear electrode position and tinnitus in cochlear implantees

Conclusion: Cochlear implant electrode position has an impact on the rate of tinnitus suppression and generation. Objective: Suppression of pre-operative tinnitus or a generation of a new tinnitus in cochlear implantees is a known effect of cochlear implantation. The aim of the current study was to evaluate different cochlear implant electrode positions and their relationship with tinnitus suppression and tinnitus generation. Method: This study retrospectively evaluated four groups of CI recipients with radiologically evaluated electrode positions in relation to their subjective tinnitus quality, as evaluated by an analogue loudness scale (ALS) and a questionnaire. Group 1 consisted of 19 patients with a scalar change of the electrode position. Group 2 consisted of 18 patients with a scala tympani position and a perimodiolar electrode. Group 3 consisted of 10 patients with a scala tympani position and a lateral wall electrode. Group 4 consisted of eight patients with a scala vestibuli position. Results: An overall tinnitus suppression rate of 45.9% and a generation of a new tinnitus or the deterioration of an existing one of 5.6% were observed. A significant difference in tinnitus suppression was found between groups 1 and groups 2, 3, and 4 in tinnitus suppression and tinnitus generation.     

Potential insertion complications with cochlear implant electrodes

Objectives: The aim of this discussion paper and literature review was to estimate the incidence of a variety of complications associated with the surgical placement of cochlear implant (CI) electrode arrays and to discuss the implications and management of sub-optimal electrode placement.

Results: A review of the peer-reviewed literature suggests that the incidence of incomplete electrode insertion and kinking is more prevalent in straight arrays and not more than about 2% in CI recipients with normal cochlear anatomy/patency. Incidence of tip fold-over is greater with perimodiolar arrays but also occurs with straight arrays and is typically less than 5%. Conversely, electrode migration is more common with straight arrays, and high rates (up to 46%) have been reported in some studies. Scalar translocations have also been reported for both perimodiolar and straight arrays. Higher rates have been reported for stylet-based perimodiolar electrodes inserted via cochleostomy (up to 56%), but with much lower rates (<10%) with both sheath-based perimodiolar arrays and lateral wall arrays.

Electrode positioning complications represent a significant proportion of perioperative CI complications and compromise the level of benefit from the device. Careful surgical planning and appropriate pre- and intraoperative imaging can reduce the likelihood and impact of electrode positioning complications. There is also evidence that newer array designs are less prone to certain complications, particularly scalar translocation.

Conclusions: It is important that implanting surgeons are aware of the impact of sub-optimal electrode placement and the steps that can be taken to avoid, identify and manage such complications.     

人工耳蜗电极植入耳蜗入口的定位

目的 :确定人工耳蜗电极植入耳蜗入口的位置。方法 :对 2 5具尸头 50耳标本进行人工耳蜗植入手术有关的解剖数据测量。结果 :人工耳蜗电极植入耳蜗鼓阶入口与前庭窗最近距离为 2 .77mm。结论 :该解剖参数为蜗窗难以找到的人工耳蜗植入病例提供了定位参考     

Evaluation of simplified programs using the MED-EL C40+ cochlear implant

Abstract

The present study evaluated the benefit possible from a cochlear implant (CI) using a simplified map (with a set of default parameters), rather than the conventional approach of producing a ‘customized map’ from electrode-specific psychophysical measures. Young children are sometimes initially provided with such maps and the aim was to gain an insight into what level of benefit they might provide. Maps with upper stimulation levels set equally across the array (i.e. ‘flat’ maps) were compared with normal ‘customized’ maps in established adult users of the MED-EL C40+ device. Speech discrimination was significantly poorer for the flat maps overall (mean of 72.7% for customized map, and 60.5% for flat map) and loudness balance estimates showed a range of degrees of imbalance. These results suggest that flat maps may provide paediatric CI users with useful levels of performance when psychophysical or objective measures cannot be obtained. The poorer performance with the flat map suggests that customized maps should be fit as soon as possible to provide paediatric patients with the maximum benefit of the CI device.

Sumario

El presente estudio evaluó el posible beneficio de un implante coclear (IC) usando un mapa simplificado (con un set preestablecido de parámetros), en vez del enfoque convencional para hacer “mapas a la medida” a partir de mediciones electrofisiológicas específicas. Los niños pequeños reciben a veces inicialmente este tipo de mapas con el objetivo de ganar conciencia sobre el nivel de beneficio que pueden proveer. Los mapas con niveles de estimulación elevados, similares en todos sus puntos (p. Ej. mapas “planos”) se compararon con mapas normales “a la medida” de usuarios adultos del MED-EL 40. La discriminación del lenguaje fue de manera global significativamente más pobre con los mapas planos (media de 72.7% con mapas a la medida y 60.5% con mapas planos) y la estimación del balance de intensidad subjetiva mostró rangos de niveles no balanceados. Estos resultados sugieren que los mapas planos pueden dar a niños usuarios de IC, niveles útiles de rendimiento cuando no pueden obtenerse mediciones psicofísicas u objetivas. El rendimiento más pobre con mapas planos sugiere que los mapas a la medida deben adaptarse apenas sea posible, para que los niños tengan el máximo beneficio de su IC.     

蜗轴与鼓阶周壁电阻抗的研究

目的:观察鼓阶内壁与蜗轴之间的阻抗是否低于鼓阶外壁与蜗轴之间的阻抗。方法:6例颞骨标本,分别在鼓阶不同位置测量蜗轴和鼓阶内、外侧壁之间的阻抗,刺激频率分别为0.1、1.0、10.0 kHz。结果:鼓阶内侧壁与蜗轴之间的阻抗明显小于相同位置下鼓阶外侧壁与鼓阶外侧壁之间的阻抗(P<0.05)。结论:为了有效刺激蜗轴的残余螺旋神经节神经元,人工耳蜗植入电极应该尽量靠近鼓阶内侧壁。     

Electrocochleography in cochlear implantation: Development,applications, and future directions

Electrocochleography (ECochG) is an electrophysiological technique that records electrical potentials generated by different components of the inner ear and peripheral cochlear nerve in response to acoustic stimulation. ECochG responses can be analyzed into (1) cochlear microphonics (CM), (2) auditory nerve neurophonics, (3) summating potential, and (4) compound action potential. Over the past few decades, there have been ongoing refinements in technique and updates in the understanding of recorded potentials. Historically, ECochG found its main application in the diagnostic evaluation of Meniere’s disease (MD). However, in the last decade, the focus has shifted towards cochlear implantation (CI). In patients with residual hearing after CI, combined electric and acoustic stimulation has resulted in improved hearing and speech outcomes. Despite efforts to mitigate trauma during electrode insertion, hearing preservation rates vary after surgery. During implantation, real-time ECochG offers an opportunity to measure frequency specific CMs elicited from a localized region in the cochlea as the surgeon inserts the electrode array. In extracochlear ECochG recordings, the recording electrode can be placed on the promontory, the stapes, or the tympanic membrane. Intracochlear ECochG can be performed by inserting a recording electrode into the cochlea or by using one of the CI electrodes as the recording electrode. The loss of intraoperative ECochG signal may indicate cochlear trauma from electrode insertion, but the association between intraoperative ECochG changes and cochlear trauma remains controversial. The ability to monitor cochlear trauma during CI electrode placement holds promise to improve hearing preservation outcomes, modify surgical techniques, and change electrode design. The goal of this review is to provide a comprehensive overview of the electrophysiology and history of ECochG, discuss its recent applications in CI, and explore the ongoing research in this expanding field.     

Cone beam computed tomography and histological evaluations of a straight electrode array positioning in temporal bones

Conclusion: CBCT allows a precise evaluation of the dimensions and of the shape of the cochlear duct that is of primary importance for the choice of the length and the design of the electrode array. This radio-histological study confirms that CBCT is a reliable tool to be used in clinical studies to evaluate the position of straight electrode arrays within the cochlear scala.

Objective: To validate the reliability of cone beam computed tomography (CBCT) in the evaluation of cochlear anatomy and positioning of a straight electrode array, by comparing radiological images to histological analysis of cochlear implanted temporal bones.

Methods: Eight temporal bones for four subjects were analysed before and after cochlear implantation with a straight electrode array. The size of the cochlea, the dimensions, and shape of the cochlear duct at 180° and 360° were evaluated on CBCT performed before implantation. Temporal bones then underwent histological analysis to determine the position of the electrode array. Scalar localization of the electrode array was assessed on CBCT performed after implantation, and compared with histological study.

Results: CBCT is a reliable radiological technique to differentiate variability not only of cochlear dimensions, but also of size and shape of the cochlea. Histological analysis confirmed the scalar position of the electrode array assessed by the CBCT in 7/8 temporal bones, but soft tissue trauma such as dissection of the spiral ligament was not identified by the CBCT.     

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.     

Reimplantation with a conventional length electrode following residual hearing loss in four hybrid implant recipients

Abstract

Hypothesis

Revision surgery using a newer-generation conventional length cochlear implant electrode will provide improved speech perception in patients that initially underwent hybrid electrode implantation and experienced post-operative loss of residual hearing and performance deterioration.

Clinical presentation

We present four patients who experienced delayed post-operative hearing loss following implantation with the Nucleus Hybrid S8 device and underwent reimplantation with the Nucleus Freedom or Nucleus 5 device using the Contour Advance array. Pure-tone thresholds and speech perception data were retrospectively reviewed.

Intervention

Four subjects underwent reimplantation with the Nucleus Freedom or Nucleus 5 device after experiencing deteriorating performance related to delayed acoustic hearing loss. Comparison of pre-revision performance to the most recent post-revision performance demonstrated improved speech perception performance in all subjects following reimplantation.

Conclusions

A small percent of patients will experience a significant loss of residual low-frequency hearing following hybrid implantation thereby becoming completely reliant on a shorter electrode for electrical stimulation. In the current series, reimplantation with a conventional length electrode provided improved speech perception performance in such patients. Revision surgery with a conventional length electrode should be considered in ‘short electrode’ recipients who experience performance deterioration following loss of residual hearing.     

Electrode failure and device failure in adult cochlear implantation

Abstract

Objectives

To determine the prevalence of cochlear implant electrode failure and the relationship with overall device failure.

Methods

Electrode status was analyzed in 322 functioning and in-use devices from 366 adult cochlear implant patients currently followed at our center. An additional 21 devices that had been explanted were also analyzed. Electrode failure was defined as unacceptably high impedance alone or in combination with aberrant percepts.

Results

At least one electrode had been turned off in 173 devices (54%). Most deactivated electrodes were the basal-most and had been turned off to improve sound quality. Of 437 deactivated electrodes, 33 were considered to have failed and were represented in 22 devices. These 22 devices are still in use (mean: 43.0 ± 29.8 months) without further electrode failures or device failure. There were no statistically significant differences in electrode failure rates among device manufacturers. There were 21 devices explanted of which 10 were due to device failure. One of five hard failures and two of three soft failures had deactivated electrodes prior to explantation. Two failures had no electrode data available.

Discussion

An inherent risk of cochlear implantation, as with all implanted electrical prostheses, is device failure. Failure of individual electrodes has been postulated to represent an early indicator of impending device failure. Our data demonstrate that electrode failure does not necessarily predict impending device failure. Although maps containing deactivated electrodes are fairly common, electrode failure as a reason for bypassing an electrode is rare and is often manageable with programming.     

Nucleus24M型人工耳蜗植入后电极阻抗的变化

目的：研究人工耳蜗植入后电极阻抗的变化规律，以便确定术后进行映射调图的时间表。方法：对16例植入Nucleus CI24M型人工耳蜗患者，于术中及术后1、1．5、2、4、6个月进行电极阻抗测试，统计分析电极阻抗的变化规律。结果：患者电极阻抗在术中检测时最低，开机时最高，以后若干次随访时，阻抗逐渐下降，并在2～4个月左右趋于稳定。结论：电极阻抗的稳定提示耳蜗内生物组织的病理过程渐趋稳定；对心理物理测试配合良好的患者，术后只进行2～4个月左右的映射调图即可。     

Protecting against electrode insertion trauma using dexamethasone

Objective: To compare the benefits of a dexamethasone-eluting array for hearing preservation and cochlear histopathology in low trauma (soft-surgery) and high trauma models of cochlear implant surgery.

Methods: Adult guinea pigs were implanted with an intra-cochlear array using two different surgical procedures: either a soft-surgery approach or following generation of electrode insertion trauma (high trauma). Two methods of dexamethasone delivery were evaluated: elution from an electrode array alone, and elution from a cochlear implant electrode array in combination with a pre-operative systemic injection. All electrode arrays were implanted for a period of 4 weeks. Outcome measures at 4 weeks post-implantation included auditory brainstem response (ABR) thresholds, histological analysis of spiral ganglion neuron density, fibrotic tissue, new bone growth, and cochlear damage.

Results: Animals exposed to high surgical trauma showed greater hearing loss than those in the low trauma model, irrespective of the presence of dexamethasone. Whilst the area of intra-cochlear fibrotic tissue growth post-implantation was also independent of dexamethasone administration, new bone growth was significantly reduced in its presence. Our high trauma model effectively obliterated the organ of Corti and significantly reduced spiral ganglion neuron densities in the lower basal turn. This trauma-induced reduction in spiral ganglion neuron survival decreased with the inclusion of a dexamethasone-eluting array. A pre-operative systemic injection of dexamethasone did not significantly improve any outcome measures beyond those provided with a dexamethasone-eluting array alone.

Conclusion: Dexamethasone-eluting intra-cochlear arrays may inhibit osteoneogenesis, and reduce spiral ganglion neuron loss following traumatic cochlear implantation.