Vestibular function and hearing preservation in children following a minimally invasive cochlear implantation

PURPOSE

This retrospective cohort study aimed to investigate the effect of minimally invasive cochlear implantation (CI) on the vestibular function (VF) and residual hearing (RH) as well as their relationship in pediatric recipients before and after surgery.

METHODS

Twenty-four pediatric patients with preoperative low frequency residual hearing (LFRH) (250 or 500 Hz ≤ 80 dB HL) who underwent minimally invasive CI were enrolled. Pure-tone thresholds, the cervical/ocular vestibular-evoked myogenic potential (cVEMP/oVEMP), and video head impulse test (vHIT) were all evaluated in the 24 pediatric patients with preoperative normal VF before and at 1 and 12 months after surgery. The relationship between changes in hearing and VF was analyzed preoperatively and at 1 and 12 months postoperatively.

RESULTS

There were no significant differences on VF preservation and hearing preservation (HP) at both 1 and 12 months post-CI (p > 0.05). At 1 month post-CI, the correlations of the variations in vestibulo-ocular reflex (VOR) gains of horizontal semicircular canal (HSC) and posterior semicircular canal (PSC) and the shift in 250 Hz threshold were negatively correlated (r = - 0.41, p = 0.04 and r = - 0.43, p = 0.04, respectively). At 12 months post-CI, the shift in 250 Hz threshold negatively correlated to the variations in VOR gain of superior semicircular canal (SSC) (r = - 0.43, p = 0.04); the HP positively correlated to the variation in oVEMP-amplitude ratio (AR) (r = 0.41, p = 0.04).

CONCLUSION

Our study confirmed that there were partial correlations between VF preservation and HP both in the short- and long-terms after atraumatic CI surgery, especially with the 250 Hz threshold. Regarding the variation of PSC function, the correlation with hearing status was variable with time after atraumatic CI surgery. Minimally invasive techniques for HP are successful and effective for the preservation of VF in pediatric patients both in the short- and long-terms.

Exploring Trauma Patterns and Contributing Factors With Slim Straight Electrode Array After Cochlear Implantation

OBJECTIVE

To assess trauma patterns associated with the insertion of lateral wall electrode arrays. The study focused on 3 categories-scala tympani (ST), intermediate, and scala vestibuli (SV)-to identify traumatic patterns and contributing factors.

STUDY DESIGN

Retrospective study.

SETTING

Data from 106 cochlear implant recipients at a tertiary otologic center.

METHODS

Demographic and surgical data were collected from recipients who underwent cochlear implantation manually and with RobOtol®. Measurements included cochlear dimensions, angular depth of insertion, and position of the first electrode. Three-dimensional reconstructions were used to analyze the electrode array location relative to the basilar membrane, categorized into ST, intermediate, and SV electrodes. Nontraumatic insertion was defined as all electrodes in the ST, while traumatic insertions had 1 or more electrodes in intermediate or SV locations.

RESULTS

Out of 106 cases, 44% had nontraumatic and 56% had traumatic insertions. Demographic and surgical characteristics showed no association with traumatic insertions. A deeper position of the first electrode, relative to the round window, was associated with traumatic insertions (P = .03). Three trauma patterns were observed: distal (facing the apical electrodes), proximal (facing the middle electrodes around 180°), and distal/proximal.

CONCLUSION

This study considers the intermediate position which could be associated with basilar membrane lesions. Risk zones for intracochlear trauma with lateral wall arrays were identified distally and proximally. Traumatic insertions were independently linked to deeper array placement. Future studies should explore whether gentler insertion, without insisting on further electrode array insertion depth, could reduce the trauma during cochlear implantation.

On the Design, Fabrication, and Characterization of a Novel Thin-Film Electrode Array for Use in Cochlear Implants

Thin-film electrode arrays (TFEAs) have been developed as an alternative to conventional electrode arrays (CEAs) used in cochlear implants. However, TFEAs produced by microfabrication techniques have not yet been used clinically because their structural and mechanical properties are far from those of CEAs. The aim of this study is to design, fabricate, and investigate the mechanical and tribological behavior and evaluate the performance of different TFEA designs. Finite Element Analysis (FEA) is performed to determine the elastic properties of several designs. A custom-build experimental setup is designed to observe the tribological behavior in different speeds and environments where frictional (lateral) and vertical force (normal force) are measured on a flat surface and within artificial cochlea. According to the FEA results, the maximum stiffness of the CEA is 37.93 mN/mm and 0.363 mN/mm and TFEA-4 has a maximum stiffness of 39.08 mN/mm and 0.306 mN/mm in the longitudinal and transverse axes, respectively. It is shown experimentally that adding a dummy wire to the carrier of the EA enhances both its longitudinal and transverse stiffness, thereby postponing the initiation of dynamic sliding due to the elevated buckling limit. It is also revealed that the type of TFEA support structure affects both normal and frictional forces, as well as the coefficient of friction.

Comparison of postural control and space perception outcomes between robotic and conventional cochlear implantation in adults

PURPOSE

The aim of the study is to capture the difference between the groups in direct relation to the type of electrode array insertion during cochlear implantation (CI). The robotic insertion is expected to be a more gently option. As recent studies have shown, there is a difference in perception of visual vertical (SVV) and postural control related to the CI. We assume that there can be differences in postural control and space perception outcomes depending on the type of the surgical method.

METHODS

In total, 37 (24 females, mean age ± SD was 42.9 ± 13.0) candidates for CI underwent an assessment. In 14 cases, the insertion of the electrode array was performed by a robotic system (RobOtol, Colin, France) and 23 were performed conventionally. In all of these patients, we performed the same examination before the surgery, the first day, and 3 weeks after the surgery. The protocol consists of static posturography and perception of visual vertical.

RESULTS

The both groups, RobOtol and conventional, responded to the procedure similarly despite the dissimilar electrode insertion. There was no difference between two groups in the dynamic of perception SVV and postural parameters. Patients in both groups were statistically significantly affected by the surgical procedure, SVV deviation appeared in the opposite direction from the implanted ear: 0.90° ± 1.25; - 1.67° ± 3.05 and - 0.19° ± 1.78 PRE and POST surgery (p < 0.001). And this deviation was spontaneously adjusted in FOLLOW-UP after 3 weeks (p < 0.01) in the both groups. We did not find a significant difference in postural parameters between the RobOtol and conventional group, even over time.

CONCLUSION

Although the robotic system RobOtol allows a substantial reduction in the speed of insertion of the electrode array into the inner ear, our data did not demonstrate a postoperative effect on vestibular functions (SVV and posturography), which have the same character and dynamics as in the group with standard manual insertion.

REGISTRATION NUMBER

The project is registered on clinicaltrials.gov (registration number: NCT05547113).

Entirely robotic cochlear implant surgery

INTRODUCTION

Robot-assisted cochlear implant surgery (RACIS) as defined by the HEARO®-procedure performs minimal invasive cochlear implant (CI) surgery by directly drilling a keyhole trajectory towards the inner ear. Hitherto, an entirely robotic automation including electrode insertion has not been described yet. The feasability of using a newly developed, dedicated motorised device for automated electrode insertion in the first clinical case of entirely robotic cochlear implant surgery was investigated.

AIM

The aim is to report the first experience of entirely robotic cochlear implantation surgery.

INTERVENTION

RACIS with a straight flexible lateral wall electrode.

PRIMARY OUTCOME MEASUREMENTS

Electrode cochlear insertion depth.

SECONDARY OUTCOME MEASUREMENTS

The audiological outcome in terms of mean hearing thresholds.

CONCLUSION

Here, we report on a cochlear implant robot that performs the most complex surgical steps to place a cochlear implant array successfully in the inner ear and render similar audiological results as in conventional surgery. Robots can execute tasks beyond human dexterity and will probably pave the way to standardize residual hearing preservation and broadening the indication for electric-acoustic stimulation in the same ear with hybrid implants.

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.

Intraoperative Measurement of Insertion Speed in Cochlear Implant Surgery: A Preliminary Experience with Cochlear SmartNav

OBJECTIVES

The objectives were to present the real-time estimated values of cochlear implant (CI) electrode insertion speed (IS) during intraoperative sessions using the Cochlear Nucleus SmartNav System to assess whether this measure affected CI outcomes and to determine whether real-time feedback assists expert surgeons in achieving slow insertion.

METHODS

The IS was measured in 52 consecutive patients (65 implanted ears) using the CI632 electrode. The IS values were analyzed in relation to procedure repetition over time, NRT ratio, and CI audiological outcomes.

RESULTS

The average IS was 0.64 mm/s (SD = 0.24); minimum and maximum values were 0.23 and 1.24 mm/s, respectively. The IS significantly decreased with each array insertion by the operator (p = 0.006), and the mean decreased by 24% between the first and last third of procedures; however, this reduction fell within the error range of SmartNav for IS (+/-0.48 mm/s). No correlation was found between IS and the NRT ratio (p = 0.51), pure-tone audiometry (PTA) at CI activation (p = 0.506), and PTA (p = 0.94) or word recognition score (p = 0.231) at last evaluation.

CONCLUSIONS

The estimated IS reported by SmartNav did not result in a clinically significant reduction in insertion speed or an improvement in CI hearing outcomes. Real-time feedback of IS could potentially be used for training, but its effectiveness requires confirmation through additional studies and more accurate tools. Implementation of IS assessment in clinical practice will enable comparisons between measurement techniques and between manual and robot-assisted insertions. This will help define the optimal IS range to achieve better cochlear implant (CI) outcomes.

Human Histology after Structure Preservation Cochlear Implantation via Round Window Insertion

OBJECTIVES

Current surgical techniques aim to preserve intracochlear structures during cochlear implant (CI) insertion to maintain residual cochlear function. The optimal technique to minimize damage, however, is still under debate. The aim of this study is to histologically compare insertional trauma and intracochlear tissue formation in humans with a CI implanted via different insertion techniques.

METHODS

One recent temporal bone from a donor who underwent implantation of a full-length CI (576°) via round window (RW) insertion was compared with nine cases implanted via cochleostomy (CO) or extended round window (ERW) approach. Insertional trauma was assessed on H&E-stained histological sections. 3D reconstructions were generated and virtually re-sectioned to measure intracochlear volumes of fibrosis and neo-ossification.

RESULTS

The RW insertion case showed electrode translocation via the spiral ligament. 2/9 CO/ERW cases showed no insertional trauma. The total volume of the cochlea occupied by fibro-osseous tissue was 10.8% in the RW case compared with a mean of 30.6% (range 8.7%-44.8%, N = 9) in the CO/ERW cases. The difference in tissue formation in the basal 5 mm of scala tympani, however, was even more pronounced when the RW case (12.3%) was compared with the cases with a CO/ERW approach (mean of 93.8%, range 81% to 100%, N = 9).

CONCLUSIONS

Full-length CI insertions via the RW can be minimally traumatic at the cochlear base without inducing extensive fibro-osseous tissue formation locally. The current study further supports the hypothesis that drilling of the cochleostomy with damage to the endosteum incites a local tissue reaction.

LEVEL OF EVIDENCE

4: Case-control study Laryngoscope, 134:945-953, 2024.

Combining Intraoperative Electrocochleography with Robotics-Assisted Electrode Array Insertion

OBJECTIVE

To describe the use of robotics-assisted electrode array (EA) insertion combined with intraoperative electrocochleography (ECochG) in hearing preservation cochlear implant surgery.

STUDY DESIGN

Prospective, single-arm, open-label study.

SETTING

All procedures and data collection were performed at a single tertiary referral center.

PATIENTS

Twenty-one postlingually deaf adult subjects meeting Food and Drug Administration indication criteria for cochlear implantation with residual acoustic hearing defined as thresholds no worse than 65 dB at 125, 250, and 500 Hz.

INTERVENTION

All patients underwent standard-of-care unilateral cochlear implant surgery using a single-use robotics-assisted EA insertion device and concurrent intraoperative ECochG.

MAIN OUTCOME MEASURES

Postoperative pure-tone average over 125, 250, and 500 Hz measured at initial activation and subsequent intervals up to 1 year afterward.

RESULTS

Twenty-two EAs were implanted with a single-use robotics-assisted insertion device and simultaneous intraoperative ECochG. Fine control over robotic insertion kinetics could be applied in response to changes in ECochG signal. Patients had stable pure-tone averages after activation with normal impedance and neural telemetry responses.

CONCLUSIONS

Combining robotics-assisted EA insertion with intraoperative ECochG is a feasible technique when performing hearing preservation implant surgery. This combined approach may provide the surgeon a means to overcome the limitations of manual insertion and respond to cochlear feedback in real-time.

Robotic assistance during cochlear implantation: the rationale for consistent, controlled speed of electrode array insertion

Cochlear implants (CI) have revolutionized the treatment of patients with severe to profound sensory hearing loss by providing a method of bypassing normal hearing to directly stimulate the auditory nerve. A further advance in the field has been the introduction of "hearing preservation" surgery, whereby the CI electrode array (EA) is carefully inserted to spare damage to the delicate anatomy and function of the cochlea. Preserving residual function of the inner ear allows patients to receive maximal benefit from the CI and to combine CI electric stimulation with acoustic hearing, offering improved postoperative speech, hearing, and quality of life outcomes. However, under the current paradigm of implant surgery, where EAs are inserted by hand, the cochlea cannot be reliably spared from damage. Robotics-assisted EA insertion is an emerging technology that may overcome fundamental human kinetic limitations that prevent consistency in achieving steady and slow EA insertion. This review begins by describing the relationship between EA insertion speed and generation of intracochlear forces and pressures. The various mechanisms by which these intracochlear forces can damage the cochlea and lead to worsened postoperative outcomes are discussed. The constraints of manual insertion technique are compared to robotics-assisted methods, followed by an overview of the current and future state of robotics-assisted EA insertion.

Comparative study of vestibular function preservation in manual versus robotic-assisted cochlear implantation

OBJECTIVE

To compare vestibular outcomes in cochlear implant (CI) surgery, between robotic-assisted insertion of the electrodes versus manual insertion.

METHODS

We performed a monocentric retrospective study. From March 2021, the robotic system RobOtol© was used for all CI cases. We compared this robotic-assisted insertion group with a manual insertion group of patients who received a CI between July 2020 and March 2021. Primary objective was vestibular outcome. We used objective vestibular function tests: caloric testing, Vestibular Evoked Myogenic Potential (VEMP), and Video Head Impulse Test (VHIT). Secondary objectives were postoperative complications including patient-reported postoperative vertigo.

RESULTS

We found no statistically significant difference between the two groups in terms of caloric testing, VEMP or VHIT outcomes. In patient-reported outcomes, there was significantly more vertigo in the manual insertion group compared with robotic-assisted insertion.

CONCLUSION

It is hypothesized that a non-traumatic insertion would cause less vestibular dysfunction postoperatively. Larger prospective studies are required to determine whether robotic-assisted CI insertion has a significant impact on vestibular outcomes in CI surgery.

Evaluation of Real-Time Intracochlear Electrocochleography for Guiding Cochlear Implant Electrode Array Position

This study evaluates intracochlear electrocochleography (ECochG) for real-time monitoring during cochlear implantation. One aim tested whether adjusting the recording electrode site would help differentiate between atraumatic and traumatic ECochG amplitude decrements. A second aim assessed whether associations between ECochG amplitude decrements and post-operative hearing loss were weaker when considering hearing sensitivity at the ECochG stimulus frequency compared to a broader frequency range. Eleven adult cochlear implant recipients who were candidates for electro-acoustic stimulation participated. Single-frequency (500-Hz) ECochG was performed during cochlear implantation; the amplitude of the first harmonic of the difference waveform was considered. Post-operative hearing preservation at 500 Hz ranged from 0 to 94%. The expected relationship between ECochG amplitude decrements and hearing preservation was observed, though the trend was not statistically significant, and predictions were grossly inaccurate for two participants. Associations did not improve when considering alternative recording sites or hearing sensitivity two octaves above the ECochG stimulus frequency. Intracochlear location of a moving recording electrode is a known confound to real-time interpretation of ECochG amplitude fluctuations, which was illustrated by the strength of the correlation with ECochG amplitude decrements. Multiple factors contribute to ECochG amplitude patterns and to hearing preservation; these results highlight the confounding influence of intracochlear recording electrode location on the ECochG.

Polymeric fiber sensors for insertion forces and trajectory determination of cochlear implants in hearing preservation

The level of hearing restoration in patients with severe to profound sensorineural hearing loss by means of cochlear implants (CIs) has drastically risen since the introduction of these neuroprosthetics. The proposed CI integrated with polymer optical fiber Bragg gratings (POFBGs) enables real-time evaluation of insertion forces and trajectory determination during implantation irrespective of the speed of insertion, as well as provides high signal quality, low stiffness levels, minimum induced stress even under forces of high magnitudes and exhibits significant reduction of the risk of fiber breakage inside the constricted cochlear geometry. As such, the proposed device opens new avenues towards atraumatic cochlear implantations and provides a direct route for the next generation of CIs with intraoperative insertion force assessment and path planning capacity crucial for surgical navigation. Hence, adaptation of this technology to clinical reality holds promising prospects for the hearing impaired.

A Steadier Hand: The First Human Clinical Trial of a Single-Use Robotic-Assisted Surgical Device for Cochlear Implant Electrode Array Insertion

OBJECTIVE

To evaluate the safety and utility of an investigational robotic-assisted cochlear implant insertion system.

STUDY DESIGN

Prospective, single-arm, open-label study under abbreviated Investigational Device Exemption requirements.

SETTING

All procedures were performed, and all data were collected, at a single tertiary referral center.

PATIENTS

Twenty-one postlingually deafened adult subjects that met Food and Drug Administration indication criteria for cochlear implantation.

INTERVENTION

All patients underwent standard-of-care surgery for unilateral cochlear implantation with the addition of a single-use robotic-assisted insertion device during cochlear electrode insertion.

MAIN OUTCOME MEASURES

Successful insertion of cochlear implant electrode array, electrode array insertion time, postoperative implant function.

RESULTS

Successful robotic-assisted insertion of lateral wall cochlear implant electrode arrays was achieved in 20 (95.2%) of 21 patients. One insertion was unable to be achieved by either robotic-assisted or manual insertion methods, and the patient was retrospectively found to have a preexisting cochlear fracture. Mean intracochlear electrode array insertion time was 3 minutes 15 seconds. All implants with successful robotic-assisted electrode array insertion (n = 20) had normal impedance and neural response telemetry measures for up to 6 months after surgery.

CONCLUSIONS

Here we report the first human trial of a single-use robotic-assisted surgical device for cochlear implant electrode array insertion. This device successfully and safely inserted lateral wall cochlear implant electrode arrays from the three device manufacturers with devices approved but he Food and Drug Administration.

Three-dimensional finite element analysis on cochlear implantation electrode insertion

Studying the insertion process of cochlear implant (CI) electrode array (EA) is important to ensure successful, sufficient, and safe implantation. A three-dimensional finite element (FE) model was developed to simulate the insertion process. The cochlear structures were reconstructed from an average statistical shape model (SSM) of human cochlea. The electrode is simplified as a long and tapered beam of homogeneous elastic materials, contacting and interacting with the stiff cochlear structures. A quasi-static insertion simulation was conducted, the insertion force and the contact pressure between the electrode and the cochlear wall, were calculated to evaluate the smoothness of insertion and the risk of potential cochlear trauma. Based on this model, different EA designs were analyzed, including the Young's modulus, the straight or bended shape, the normal or a more tapped section size. The influence of the insertion angle was also discussed. Our simulations indicate that reducing the EA Young's modulus, tapering and pre-bending are effective ways to ensure safe and successful EA implantation. This model is beneficial for optimizing EA designs and is potentially useful for designing patient-specific CI surgery.

Minimally Traumatic Cochlear Implant Surgery: Expert Opinion in 2010 and 2020

This study aimed to discover expert opinion on the surgical techniques and materials most likely to achieve maximum postoperative residual hearing preservation in cochlear implant (CI) surgery and to determine how these opinions have changed since 2010. A previously published questionnaire used in a study published in 2010 was adapted and expanded. The questionnaire was distributed to an international group of experienced CI surgeons. Present results were compared, via descriptive statistics, to those from the 2010 survey. Eighteen surgeons completed the questionnaire. Respondents clearly favored the following: round window insertion, slow array insertion, and the peri- and postoperative use of systematic antibiotics. Insertion depth was regarded as important, and electrode arrays less likely to induce trauma were preferred. The usefulness of dedicated soft-surgery training was also recognized. A lack of agreement was found on whether the middle ear cavity should be flushed with a non-aminoglycoside antibiotic solution or whether a sheath or insertion tube should be used to avoid contaminating the array with blood or bone dust. In conclusion, this paper demonstrates how beliefs about CI soft surgery have changed since 2010 and shows areas of current consensus and disagreement.

Automatic analysis of cochlear response using electrocochleography signals during cochlear implant surgery

Cochlear implants (CIs) provide an opportunity for the hearing impaired to perceive sound through electrical stimulation of the hearing (cochlear) nerve. However, there is a high risk of losing a patient’s natural hearing during CI surgery, which has been shown to reduce speech perception in noisy environments as well as music appreciation. This is a major barrier to the adoption of CIs by the hearing impaired. Electrocochleography (ECochG) has been used to detect intra-operative trauma that may lead to loss of natural hearing. There is early evidence that ECochG can enable early intervention to save natural hearing of the patient. However, detection of trauma by observing changes in the ECochG response is typically carried out by a human expert. Here, we discuss a method of automating the analysis of cochlear responses during CI surgery. We establish, using historical patient data, that the proposed method is highly accurate (∼94% and ∼95% for sensitivity and specificity respectively) when compared to a human expert. The automation of real-time cochlear response analysis is expected to improve the scalability of ECochG and improve patient safety.

Real-Time Data-Driven Approach for Prediction and Correction of Electrode Array Trajectory in Cochlear Implantation

Cochlear implants provide hearing perception to people with severe to profound hearing loss. The electrode array (EA) inserted during the surgery directly stimulates the hearing nerve, bypassing the acoustic hearing system. The complications during the EA insertion in the inner ear may cause trauma leading to infection, residual hearing loss, and poor speech perception. This work aims to reduce the trauma induced during electrode array insertion process by carefully designing a sensing method, an actuation system, and data-driven control strategy to guide electrode array in scala tympani. Due to limited intra-operative feedback during the insertion process, complex bipolar electrical impedance is used as a sensing element to guide EA in real time. An automated actuation system with three degrees of freedom was used along with a complex impedance meter to record impedance of consecutive electrodes. Prediction of EA direction (medial, middle, and lateral) was carried out by an ensemble of random forest, shallow neural network, and k-nearest neighbour in an offline setting with an accuracy of 86.86%. The trained ensemble was then utilized in vitro for prediction and correction of EA direction in real time in the straight path with an accuracy of 80%. Such a real-time system also has application in other electrode implants and needle and catheter insertion guidance.

Prolonged Insertion Time Reduces Translocation Rate of a Precurved Electrode Array in Cochlear Implantation

HYPOTHESIS

Insertion speed during cochlear implantation determines the risk of cochlear trauma. By slowing down insertion speed tactile feedback is improved. This is highly conducive to control the course of the electrode array along the cochlear contour and prevent translocation from the scala tympani to the scala vestibuli.

BACKGROUND

Limiting insertion trauma is a dedicated goal in cochlear implantation to maintain the most favorable situation for electrical stimulation of the remaining stimulable neural components of the cochlea. Surgical technique is one of the potential influencers on translocation behavior of the electrode array.

METHODS

The intrascalar position of 226 patients, all implanted with a precurved electrode array, aiming a mid-scalar position, was evaluated. One group (n = 113) represented implantation with an insertion time less than 25 seconds (fast insertion) and the other group (n = 113) was implanted in 25 or more seconds (slow insertion). A logistic regression analysis studied the effect of insertion speed on insertion trauma, controlled for surgical approach, cochlear size, and angular insertion depth. Furthermore, the effect of translocation on speech performance was evaluated using a linear mixed model.

RESULTS

The translocation rate within the fast and slow insertion groups were respectively 27 and 10%. A logistic regression analysis showed that the odds of dislocation increases by 2.527 times with a fast insertion, controlled for surgical approach, cochlear size, and angular insertion depth (95% CI = 1.135, 5.625). We failed to find a difference in speech recognition between patients with and without translocated electrode arrays.

CONCLUSION

Slowing down insertion speed till 25 seconds or longer reduces the incidence of translocation.

Suitable Electrode Choice for Robotic-Assisted Cochlear Implant Surgery: A Systematic Literature Review of Manual Electrode Insertion Adverse Events

Background and Objective

The cochlear implant (CI) electrode insertion process is a key step in CI surgery. One of the aims of advances in robotic-assisted CI surgery (RACIS) is to realize better cochlear structure preservation and to precisely control insertion. The aim of this literature review is to gain insight into electrode selection for RACIS by acquiring a thorough knowledge of electrode insertion and related complications from classic CI surgery involving a manual electrode insertion process.

Methods

A systematic electronic search of the literature was carried out using PubMed, Scopus, Cochrane, and Web of Science to find relevant literature on electrode tip fold over (ETFO), electrode scalar deviation (ESD), and electrode migration (EM) from both pre-shaped and straight electrode types.

Results

A total of 82 studies that include 8,603 ears implanted with a CI, i.e., pre-shaped (4,869) and straight electrodes (3,734), were evaluated. The rate of ETFO (25 studies, 2,335 ears), ESD (39 studies, 3,073 ears), and EM (18 studies, 3,195 ears) was determined. An incidence rate (±95% CI) of 5.38% (4.4–6.6%) of ETFO, 28.6% (26.6–30.6%) of ESD, and 0.53% (0.2–1.1%) of EM is associated with pre-shaped electrodes, whereas with straight electrodes it was 0.51% (0.1–1.3%), 11% (9.2–13.0%), and 3.2% (2.5–3.95%), respectively. The differences between the pre-shaped and straight electrode types are highly significant (p < 0.001). Laboratory experiments show evidence that robotic insertions of electrodes are less traumatic than manual insertions. The influence of round window (RW) vs. cochleostomy (Coch) was not assessed.

Conclusion

Considering the current electrode designs available and the reported incidence of insertion complications, the use of straight electrodes in RACIS and conventional CI surgery (and manual insertion) appears to be less traumatic to intracochlear structures compared with pre-shaped electrodes. However, EM of straight electrodes should be anticipated. RACIS has the potential to reduce these complications.

Measurement and Mitigation of Intracochlear Pressure Transients During Cochlear Implant Electrode Insertion

HYPOTHESIS

High intracochlear pressure transients associated with cochlear implant placement are reduced with smaller, non-styleted arrays, and longer insertion durations.

BACKGROUND

With increasing focus on hearing preservation during cochlear implant surgery, atraumatic technique is of the utmost importance. Previous studies revealed that high intensity pressure transients can be generated during the insertion of implant electrodes. Resulting acoustic trauma may be one contributing factor to postoperative loss of residual hearing.

METHODS

Thirty ears in cadaveric specimens were surgically prepared with placement of intracochlear pressure sensors. Sequential implant insertions were made over 10, 30, or 60 seconds using seven randomly ordered electrode styles. Pressures were also measured during common post-insertion electrode manipulations and removal. Measurements were compared between electrode styles and characteristics using analysis of variance (ANOVA) and Pearson correlation.

RESULTS

Implant insertion and post-insertion manipulations produced high-intensity pressure transients with all electrodes tested, with some measurements exceeding 170 dB peak SPL. Average peak pressures were significantly lower for straight, non-stylet electrodes (p << 0.001). The likelihood of generating transients was lowest with the slowest insertions (p << 0.001).

CONCLUSIONS

Cochlear implant insertion can generate transients in intralabyrinthine pressure levels equivalent to high intensity, impulsive acoustic stimuli known to cause hearing loss. Although transients were observed in all conditions, exposure may be mitigated by using non-styleted electrodes and slow insertion speeds. Additional surgical manipulations can also produce similar high-pressure events. Results from this investigation suggest that use of non-styleted electrodes, slow but steady insertion speeds, and avoidance of post-insertional manipulations are important to reduce cochlear trauma.

Robotics, automation, active electrode arrays, and new devices for cochlear implantation: A contemporary review

In the last two decades, cochlear implant surgery has evolved into a minimally invasive, hearing preservation surgical technique. The devices used during surgery have benefited from technological advances that have allowed modification and possible improvement of the surgical technique. Robotics has recently gained popularity in otology as an effective tool to overcome the surgeon's limitations such as tremor, drift and accurate force control feedback in laboratory testing. Cochlear implantation benefits from robotic assistance in several steps during the surgical procedure: (i) during the approach to the middle ear by automated mastoidectomy and posterior tympanotomy or through a tunnel from the postauricular skin to the middle ear (i.e. direct cochlear access); (ii) a minimally invasive cochleostomy by a robot-assisted drilling tool; (iii) alignment of the correct insertion axis on the basal cochlear turn; (iv) insertion of the electrode array with a motorized insertion tool. In recent years, the development of bone-attached parallel robots and image-guided surgical robotic systems has allowed the first successful cochlear implantation procedures in patients via a single hole drilled tunnel. Several other robotic systems, new materials, sensing technologies applied to the electrodes, and smart devices have been developed, tested in experimental models and finally some have been used in patients with the aim of reducing trauma in cochleostomy, and permitting slow and more accurate insertion of the electrodes. Despite the promising results in laboratory tests in terms of minimal invasiveness, reduced trauma and better hearing preservation, so far, no clinical benefits on residual hearing preservation or better speech performance have been demonstrated. Before these devices can become the standard approach for cochlear implantation, several points still need to be addressed, primarily cost and duration of the procedure. One can hope that improvement in the cost/benefit ratio will expand the technology to every cochlear implantation procedure. Laboratory research and clinical studies on patients should continue with the aim of making intracochlear implant insertion an atraumatic and reversible gesture for total preservation of the inner ear structure and physiology.

Cochlear Size Assessment Predicts Scala Tympani Volume and Electrode Insertion Force- Implications in Robotic Assisted Cochlear Implant Surgery

Objectives: The primary aim was to measure the volume of the scala tympani (ST) and the length of the straight portion of the cochlear basal turn from micro-computed tomography (μCT) images. The secondary aim was to estimate the electrode insertion force based on cochlear size and insertion speed. Both of these objectives have a direct clinical relevance in robotic assisted cochlear implant (CI) surgery.

Methods: The ST was segmented in thirty μCT datasets to create a three-dimensional (3D) model and calculate the ST volume. The diameter (A-value), the width (B-value), and the straight portion of the cochlear basal turn (S-value) were measured from the oblique coronal plane. Electrode insertion force was measured in ST models of two different sizes, by inserting FLEX24 (24 mm) and FLEX28 (28 mm) electrode arrays at five different speeds (0.1, 0.5, 1, 2, and 4 mm/s).

Results: The mean A-, B-, and S-values measured from the 30 μCT datasets were 9.0 ± 0.5, 6.7 ± 0.4, and 6.9 mm ± 0.5, respectively. The mean ST volume was 34.2 μl ± 7 (range 23–50 μl). The ST volume increased linearly with an increase in A- and B-values (Pearson's coefficient r = 0.55 and 0.56, respectively). The A-value exhibited linear positive correlation with the B-value and S-value (Pearson's coefficient r = 0.64 and r = 0.66, respectively). In the smaller of the two ST models, insertion forces were higher across the range of insertion speeds during both array insertions, when compared to the upscaled model. Before the maximum electrode insertion depths, a trend toward lower insertion force for lower insertion speed and vice-versa was observed.

Conclusion: It is important to determine pre-operative cochlear size as this seems to have an effect upon electrode insertion forces. Higher insertion forces were seen in a smaller sized ST model across two electrode array lengths, as compared to an upscaled larger model. The ST volume, which cannot be visualized on clinical CT, correlates with clinical cochlear parameters. This enabled the creation of an equation capable of predicting ST volume utilizing A- and B-values, thus enabling pre-operative prediction of ST volume.

Finite element modelling of the surgical procedure for placement of a straight electrode array: Mechanical and clinical consequences

A cochlear implant is an electronic device implanted into the cochlea to directly stimulate the auditory nerve. Such device is used in patients with severe-to-profound hearing loss. The cochlear implant surgery is safe, but involves some risks, such as infections, device malfunction or damage of the facial nerve and it can result on a poor hearing outcome, due to the destruction of any present residual hearing. Future improvements in cochlear implant surgery will necessarily involve the decrease of the intra-cochlear damage. Several implant related variables, such as materials, geometrical design, processor and surgical techniques can be optimized in order for the patients to partially recover their hearing capacities The straight electrode is a type of cochlear implant that many authors indicate as being the less traumatic. From the finite element analysis conducted in this work, the influence of the insertion speed, the friction coefficient between the cochlear wall and the electrode array, and several configurations of the cochlear implant tip were studied. The numerical simulations of the implantation showed the same pattern of the insertion force against insertion depth, thus indicating the different phases of the insertion. Results demonstrated that lower insertion speeds, friction coefficients and tip stiffness, led to a reduction on the contact pressures and insertion force. It is expected that these improved configurations will allow to preserve the residual hearing while reducing surgical complications.

Refining surgical techniques for efficient posterior semicircular canal gene delivery in the adult mammalian inner ear with minimal hearing loss

Hearing loss is a common disability affecting the world's population today. While several studies have shown that inner ear gene therapy can be successfully applied to mouse models of hereditary hearing loss to improve hearing, most of these studies rely on inner ear gene delivery in the neonatal age, when mouse inner ear has not fully developed. However, the human inner ear is fully developed at birth. Therefore, in order for inner ear gene therapy to be successfully applied in patients with hearing loss, one must demonstrate that gene delivery can be safely and reliably performed in the mature mammalian inner ear. In this study, we examine the steps involved in posterior semicircular canal gene delivery in the adult mouse inner ear. We find that the duration of perilymphatic leakage and injection rate have a significant effect on the post-surgical hearing outcome. Our results show that although AAV2.7m8 has a lower hair cell transduction rate in adult mice compared to neonatal mice at equivalent viral load, AAV2.7m8 is capable of transducing the adult mouse inner and outer hair cells with high efficiency in a dose-dependent manner.

Hydraulic insertions of cochlear implant electrode arrays into the human cadaver cochlea: preliminary findings

OBJECTIVES

(1) To evaluate the feasibility of a non-invasive, novel, simple insertion tool to perform automated, slow insertions of cochlear implant electrode arrays (EA) into a human cadaver cochlea; (2) to estimate the handling time required by our tool.

METHODS

Basic science study conducted in an experimental OR. Two previously anonymized human cadaver heads, three commercially available EAs, and our novel insertion tool were used for the experiments. Our tool operates as a hydraulic actuator that delivers an EA at continuous velocities slower than manually feasible.

INTERVENTION(S)

the human cadaver heads were prepared with a round-window approach for CI surgery in a standard fashion. Twelve EA insertion trials using our tool involved: non-invasive fixation of the tool to the head; directing the tool to the round window and EA mounting onto the tool; automated EA insertion at approximately 0.1 mm/s driven by hydraulic actuation. Outcome measurement(s): handling time of the tool; post-insertion cone-beam CT scans to provide intracochlear evaluation of the EA insertions.

RESULTS

Our insertion tool successfully inserted an EA into the human cadaver cochlea (n = 12) while being attached to the human cadaver head in a non-invasive fashion. Median time to set up the tool was 8.8 (7.2-9.4) min.

CONCLUSION

The first insertions into the human cochlea using our novel, simple insertion tool were successful without the need for invasive fixation. The tool requires < 10 min to set up, which is clinically acceptable. Future assessment of intracochlear trauma is needed to support its safety profile for clinical translation.

The Use of Clinically Measurable Cochlear Parameters in Cochlear Implant Surgery as Indicators for Size, Shape, and Orientation of the Scala Tympani

OBJECTIVES

(1) To assess variations of the human intracochlear anatomy and quantify factors which might be relevant for cochlear implantation (CI) regarding surgical technique and electrode design. (2) Search for correlations of these factors with clinically assessable measurements.

DESIGN

Human temporal bone study with micro computed tomography (μCT) data and analysis of intracochlear geometrical variations: μCT data of 15 fresh human temporal bones was generated, and the intracochlear lumina scala tympani (ST) and scala vestibuli were manually segmented using custom software specifically designed for accurate cochlear segmentation. The corresponding datasets were processed yielding 15 detailed, three-dimensional cochlear models which were investigated in terms of the scalae height, cross-sectional size, and rotation as well as the interrelation of these factors and correlations to others.

RESULTS

The greatest anatomical variability was observed within the round window region of the cochlea (basal 45°), especially regarding the cross-sectional size of the ST and its orientation relative to the scala vestibuli, which were found to be correlated (p < 0.001). The cross-sectional height of the ST changes substantially for both increasing cochlear angles and lateral wall distances. Even small cochleae were found to contain enough space for all commercially available CI arrays. Significant correlations of individual intracochlear parameters to clinically assessable ones were found despite the small sample size.

CONCLUSION

While there is generally enough space within the ST for CI, strong intracochlear anatomical variations could be observed highlighting the relevance of both soft surgical technique as well as a highly flexible and self-adapting cochlear implant electrode array design. Cochlear dimensions (especially at the round window) could potentially be used to indicate surgically challenging anatomies.

Robotics for Cochlear Implantation Surgery: Challenges and Opportunities

OBJECTIVES

Recent advancements in robotics have set forth a growing body of evidence for the clinical application of the robotic cochlear implantation (RCI), with many potential benefits. This review aims to summarize these efforts, provide the latest developments in this exciting field, and explore the challenges associated with the clinical implementation of RCI.

DATA SOURCES

MEDLINE, PubMed, and EMBASE databases.

STUDY SELECTION

A search was conducted using the keywords "robotics otolaryngology," "robotic cochlear implant," "minimally-invasive cochlear implantation," "minimally-invasive mastoidectomy," and "percutaneous cochlear implant" with all of their synonyms. Literature selection criteria included articles published in English, and articles from 1970 to present.

RESULTS

The use of robotics in neurotology is a relatively new endeavor that continues to evolve. Robotics is being explored by various groups to facilitate in the various steps of cochlear implant surgery, including drilling a keyhole approach to the middle ear for implants, inner ear access, and electrode insertion into the cochlea. Initial clinical trials have successfully implanted selected subjects using robotics.

CONCLUSIONS

The use of robotics in cochlear implants remains in its very early stages. It is hoped that robotics will improve clinical outcomes. Although successful implants with robots are reported in the literature, there are some challenges that need to be addressed before this approach can become an acceptable option for the conventional cochlear implant surgery, such as safety, time, efficiency, and cost. However, it is hoped that further advancements in robotic technology will help in overcoming these barriers leading to successful implementation for clinical utility.

Magnetic Steering of Robotically Inserted Lateral-wall Cochlear-implant Electrode Arrays Reduces Forces on the Basilar Membrane In Vitro

HYPOTHESIS

Undesirable forces applied to the basilar membrane during surgical insertion of lateral-wall cochlear-implant electrode arrays (EAs) can be reduced via robotic insertion with magnetic steering of the EA tip.

BACKGROUND

Robotic insertion of magnetically steered lateral-wall EAs has been shown to reduce insertion forces in vitro and in cadavers. No previous study of robot-assisted insertion has considered force on the basilar membrane.

METHODS

Insertions were executed in an open-channel scala-tympani phantom. A force plate, representing the basilar membrane, covered the channel to measure forces in the direction of the basilar membrane. An electromagnetic source generated a magnetic field to steer investigational EAs with permanent magnets at their tips, while a robot performed the insertion.

RESULTS

When magnetic steering was sufficient to pull the tip of the EA off of the lateral wall of the channel, it resulted in at least a 62% reduction of force on the phantom basilar membrane at insertion depths beyond 14.4 mm (p < 0.05), and these beneficial effects were maintained beyond approximately the same depth, even with 10 degrees of error in the estimation of the modiolar axis of the cochlea. When magnetic steering was not sufficient to pull the EA tip off of the lateral wall, a significant difference from the no-magnetic-steering case was not found.

CONCLUSIONS

This in vitro study suggests that magnetic steering of robotically inserted lateral-wall cochlear-implant EAs, given sufficient steering magnitude, can reduce forces on the basilar membrane in the first basilar turn compared with robotic insertion without magnetic steering.

Initial Experience With a Recently Developed Lateral Wall Electrode

OBJECTIVE

To review our hearing preservation rates and speech recognition outcomes in patients undergoing cochlear implantation with a recently developed lateral wall electrode.

STUDY DESIGN

Retrospective cohort study.

METHODS

Retrospective case series of all patients, both pediatric and adult, undergoing cochlear implantation with the Advanced Bionics Hifocus™ SlimJ electrode between December 2017 and January 2020. Main outcomes included hearing preservation rates using several definitions, speech recognition testing primarily through Arizona Biosciences (AzBio) and Consonant-Nucleus-Consonant (CNC) testing, intra- and postoperative complications.

RESULTS

Sixty-one ears underwent implantation with the new electrode. Hearing preservation rates were 13.0% to 36.0% depending on the definition used. Speech recognition testing showed significant increases from pre- to postoperative condition (Implant-only AzBio: 24.1 to 48.3, P = .004, binaural AzBio: 46.1 to 65.9, P = .002, Implant-only CNC: 9.7 to 35.1, P < .001, binaural CNC: 29.8 to 59.40, P < .001) with last speech recognition testing occurring an average of 8.8 months postoperatively. The elderly population had the worst hearing preservation rates across all definitions. Five explantations were required due to two infections and three device failures.

CONCLUSION

Hearing preservation rates varied significantly depending on the definition used, but users experienced a significant improvement in speech recognition testing after implantation. More work is needed in the community to standardize the definition of residual hearing and hearing preservation.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

In-Vitro Study of Speed and Alignment Angle in Cochlear Implant Electrode Array Insertions

OBJECTIVE

The insertion of the electrode array is a critical step in cochlear implantation. Herein we comprehensively investigate the impact of the alignment angle and feed-forward speed on deep insertions in artificial scala tympani models with accurate macro-anatomy and controlled frictional properties.

METHODS

Motorized insertions (n=1033) were performed in six scala tympani models with varying speeds and alignment angles. We evaluated reaction forces and micrographs of the insertion process and developed a mathematical model to estimate the normal force distribution along the electrode arrays.

RESULTS

Insertions parallel to the cochlear base significantly reduce insertion energies and lead to smoother array movement. Non-constant insertion speeds allow to reduce insertion forces for a fixed total insertion time compared to a constant feed rate.

CONCLUSION

In cochlear implantation, smoothness and peak forces can be reduced with alignment angles parallel to the scala tympani centerline and with non-constant feed-forward speed profiles.

SIGNIFICANCE

Our results may help to provide clinical guidelines and improve surgical tools for manual and automated cochlear implantation.

The Use of a Robot to Insert an Electrode Array of Cochlear Implants in the Cochlea: A Feasibility Study and Preliminary Results

INTRODUCTION

Cochlear implants (CIs) are commonly used for the rehabilitation of profound bilateral hearing loss. However, patients with substantial residual acoustic hearing are potential CI candidates. Because of both improvements in technology and advancements in surgical techniques, it may be possible to preserve hearing to some extent. For more than a decade, it has been suggested that robots are used to perform middle ear surgery. We evaluated the use of the RobOtol® otologic robot specifically to insert CI electrodes into the inner ear.

METHODS

CI surgery with the conventional approach was performed under general anesthesia. The MED-El Flex 24-electrode array was inserted using RobOtol®. Video recordings were used to calculate the speed of insertion. The positions of the electrodes were evaluated using a cone beam CT. All subjects underwent pure-tone audiometry tests before and after surgery, and the pure-tone average (PTA) was calculated from 250 to 4,000 Hz.

RESULTS

The robot inserted implants in 5 patients, and complete insertion of the electrode array was achieved. The speed of insertion of the electrode array was 0.88 ± 0.12 mm/s. The mean loss of the PTA for 5 frequencies (250, 500, 1,000, 2,000, and 4,000 Hz) was 13.60 ± 7.70 dB. Only 1 patient showed a loss of the PTA by >20 dB. For these 5 patients, the cone beam CT findings showed that all the electrode arrays were in the tympanic ramp and had a grade of 0. The results were compared with those obtained from a cohort of 17 patients who underwent manual implantation of a MED-El Flex 24-electrode array.

CONCLUSION

To minimize disturbance to the cochlea while atraumatic electrode arrays are inserted, electrodes can be inserted at a constant, slow speed in the inner ear with the assistance of the RobOtol® robot in a normal clinical surgical setting.

Robot-assisted Cochlear Implant Electrode Array Insertion in Adults: A Comparative Study With Manual Insertion

OBJECTIVE

To describe the first cochlear array insertions using a robot-assisted technique, with different types of straight or precurved electrode arrays, compared with arrays manually inserted into the cochlea.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary otologic center.

PATIENTS

Twenty cochlear implantations in the robot-assisted group and 40 in the manually inserted group.

INTERVENTIONS

Cochlear implantations using a robot-assisted technique (RobOtol) with straight (eight Cochlear CI522/622, and eight Advanced Bionics Hifocus Slim J) or precurved (four Advanced Bionics Hifocus Mid-Scala) matched to manual cochlear implantations. Three-dimensional reconstruction images of the basilar membrane and the electrode array were obtained from pre- and postimplantation computed tomography.

MAIN OUTCOME MEASURES

Rate and localization of scalar translocations.

RESULTS

For straight electrode arrays, scalar translocations occurred in 19% (3/16) of the robot-assisted group and 31% (10/32) of the manually inserted group. Considering the number of translocated electrodes, this was lower in the robot-assisted group (7%) than in the manually inserted group (16%) (p < 0.0001, χ2 test). For precurved electrode arrays, scalar translocations occurred in 50% (2/4) of the robot-assisted group and 38% (3/8) of the manually inserted group.

CONCLUSION

This study showed a safe and reliable insertion of different electrode array types with a robot-assisted technique, with a less traumatic robotic insertion of straight electrode arrays when compared with manual insertion.

The Effect of Ultra-slow Velocities on Insertion Forces: A Study Using a Highly Flexible Straight Electrode Array

OBJECTIVE

The present study sought to 1) characterize insertion forces resulting from a flexible straight electrode array (EA) inserted at slow and ultra-slow insertion velocities, and 2) evaluate if ultra-slow velocities decrease insertion forces independent of other variables.

BACKGROUND

Low insertion forces are desirable in cochlear implant (CI) surgery to reduce trauma and preserve hearing. Recently, ultra-slow insertion velocities (lower than manually feasible) have been shown to produce significantly lower insertion forces using other EAs.

METHODS

Five flexible straight EAs were used to record insertion forces into an inelastic artificial scala tympani model. Eleven trial recordings were performed for each EA at five predetermined automated, continuous insertion velocities ranging from 0.03 to 1.6 mm/s.

RESULTS

An ultra-slow insertion velocity of 0.03 mm/s resulted in a median insertion force of 0.010 N at 20 mm of insertion depth, and 0.026 N at 24.3 mm-the final insertion depth. These forces represent only 24 to 29% of those measured using 1.6 mm/s. After controlling for insertion depth of the EA into the artificial scala tympani model and trial insertion number, decreasing the insertion velocity from 0.4 to 0.03 mm/s resulted in a 50% decrease in the insertion forces.

CONCLUSION

Using the tested EA ultra-slow velocities can decrease insertion forces, independent of variables like insertion depth. Our results suggest ultra-slow velocities can reduce insertion forces at least 60%, compared with humanly feasible continuous velocities (≥0.9 mm/s).

Evaluation of Insertion Forces and Cochlea Trauma Following Robotics-Assisted Cochlear Implant Electrode Array Insertion

HYPOTHESIS

The objective was to evaluate the effect of cochlear implant (CI) insertion technique on electrode insertion forces and intracochlear trauma. We hypothesize that robotics-assisted insertions will reduce insertion forces and intracochlear trauma compared with manual insertions.

BACKGROUND

Variability in CI outcomes exists across patients, implant centers, surgeons, and electrode types. While surgical techniques that reduce electrode insertion trauma are well established, insertion trauma remains one contributing factor to variability in CI outcomes. Previous work demonstrates that micromechanically controlled insertion tools reduce both maximum insertion forces and insertion variability compared with manual insertions.

METHODS

CI electrode insertions were performed either by hand (n = 12) or utilizing a robotics-assisted tool (n = 12) in fresh frozen, human cadaveric cochleae using electrodes from four different CI manufacturers. Electrodes array insertion forces were additionally evaluated in benchtop cochlea models. Following cadaveric insertions, samples were imaged via high resolution x-ray microscopy to evaluate electrode position and intracochlear trauma events based on a modified Eshraghi scale.

RESULTS

Electrode array insertions performed by robotics-assisted system showed significantly lower insertion forces and variability. Manual electrode array insertions had a significantly higher overall trauma score of 3.1 ± 2.0 compared with 0.9 ± 1.0 for robotics-assisted insertions. Robotics-assisted insertions had higher rate of basilar membrane elevations while manual insertions showed higher rates of severe trauma events.

CONCLUSIONS

The robotic-assisted insertion system reduced trauma events associated with CI electrode insertions in cadaveric cochleae compared with manual insertions. Surgical devices which help to precisely and more consistently insert electrodes may improve CI outcomes and hearing preservation.

Vestibular Organ and Cochlear Implantation-A Synchrotron and Micro-CT Study

Background: Reports vary on the incidence of vestibular dysfunction and dizziness in patients following cochlear implantation (CI). Disequilibrium may be caused by surgery at the cochlear base, leading to functional disturbances of the vestibular receptors and endolymphatic duct system (EDS) which are located nearby. Here, we analyzed the three-dimensional (3D) anatomy of this region, aiming to optimize surgical approaches to limit damage to the vestibular organ. Material and Methods: A total of 22 fresh-frozen human temporal bones underwent synchrotron radiation phase-contrast imaging (SR-PCI). One temporal bone underwent micro-computed tomography (micro-CT) after fixation and staining with Lugol's iodine solution (I2KI) to increase tissue contrast. We used volume-rendering software to create 3D reconstructions and tissue segmentation that allowed precise assessment of anatomical relationships and topography. Macerated human ears belonging to the Uppsala collection were also used. Drilling and insertion of CI electrodes was performed with metric analyses of different trajectories. Results and Conclusions: SR-PCI and micro-CT imaging demonstrated the complex 3D anatomy of the basal region of the human cochlea, vestibular apparatus, and EDS. Drilling of a cochleostomy may disturb vestibular organ function by injuring the endolymphatic space and disrupting fluid barriers. The saccule is at particular risk due to its proximity to the surgical area and may explain immediate and long-term post-operative vertigo. Round window insertion may be less traumatic to the inner ear, however it may affect the vestibular receptors.

EAS-Combined electric and acoustic stimulation

Electric-acoustic stimulation (EAS) is a special treatment modality for those patients who are profoundly deaf in the high-frequency (HF) region and retain usable hearing in the low-frequency (LF) region. Combining the electric stimulation with cochlear implant (CI) in the HF and acoustic amplification of residual hearing using a conventional hearing aid (HA) in the LF region defines EAS. The EAS concept was first proposed by C. von Ilberg from Frankfurt, Germany in the year 1997. In association with MED-EL, all the necessary safety studies were performed in non-human subjects before the first patient received it in 1997. In association with MED-EL, all the necessary safety studies were performed in non-human subjects before the first patient received it in 1999. For the patient to successfully use the EAS concept, the residual hearing needs to be preserved to a high extent and for several years. This requires a highly flexible electrode array in safeguarding the intra-cochlear structures during and after the CI electrode array insertion. Combining the HA unit with the audio processor unit of the CI was necessary for the convenient wearing of the unified audio processor. Fitting of the unified audio processor is another important factor that contributes to the overall success of the EAS treatment. The key translational research efforts at MED-EL were on the development of flexible electrodes, a unified audio processor, innovations in the fitting process, intra-operative monitoring of cochlear health during electrode insertion, pre-operative soft-ware tool to evaluate the cochlear size and electrode selection and some new innovations tried within EAS topic. This article covers the milestones of translational research from the first concept to the widespread clinical use of EAS.

Effect of Underwater Insertion on Intracochlear Pressure

Background: The importance of intracochlear pressure during cochlear electrode insertion for the preservation of residual hearing has been widely discussed. Various aspects of pre-insertional, intra-insertional, and post-insertional relevant conditions affect intracochlear pressure. The fluid situation at the round window during electrode insertion has been shown to be an influential factor.

Aims/Objectives: The aim of the study was to compare various insertion techniques in terms of the fluid situation at the round window.

Material and Methods: We performed insertion of cochlear implant electrodes in a curled artificial cochlear model. We placed and fixed the pressure sensor at the tip of the cochlea. In parallel to the insertions, we evaluated the maximum amplitude of intracochlear pressure under four different fluid conditions at the round window: (1) hyaluronic acid; (2) moisturized electrode, dry middle ear; (3) middle ear filled with fluid (underwater); and (4) moisturized electrode, wet middle ear, indirectly inserted.

Results: We observed that the insertional intracochlear pressure is dependent on the fluid situation in front of the round window. The lowest amplitude changes were observed for the moisturized electrode indirectly inserted in a wet middle ear (0.13 mmHg ± 0.07), and the highest values were observed for insertion through hyaluronic acid in front of the round window (0.64 mmHg ± 0.31).

Conclusions: The fluid state in front of the round window influences the intracochlear pressure value during cochlear implant electrode insertion in our model. Indirect insertion of a moisturized electrode through a wet middle ear experimentally generated the lowest pressure values. Hyaluronic acid in front of the round window leads to high intracochlear pressure in our non-validated artificial model.

The influence of Slim Modiolar electrode on residual hearing in pediatric patients

PURPOSE

Hearing preservation cochlear implantation is an established procedure in patients with low-frequency residual hearing, especially in pediatric cochlear implantation. More delicate, thin electrode arrays can minimize damage in the inner ear and enhance the possibility for residual hearing preservation. The Cochlear^® CI532 electrode has been reported as an electrode with the potential for residual hearing preservation. No similar studies pertaining to hearing preservation in pediatric patients have appeared to date. The aim of this study was to investigate whether the Cochlear^® CI532 Slim Modiolar electrode allows the preservation of low-frequency residual hearing in children undergoing cochlear implantation.

METHODS

In this multicenter, nonrandomized, prospective clinical cohort study, medical data of 14 pediatric patients implanted with the CI532 were collected. All patients had residual low-frequency hearing (preoperative audiogram or ABR with at least one threshold better than 90 dB HL at 125, 250, 500, or 1000 Hz). Postoperative thresholds were obtained 1, 3, 6, and 12 months after cochlear implantation.

RESULTS

Based on the HEARRING classification, 78.6% of children (11/14) had complete hearing preservation at the last follow-up visit (12 months after CI, or if not available, 6 months). A total of 21.4% (3/14) had partial hearing preservation. At the last follow-up visit, neither minimal hearing preservation nor loss of hearing was observed. Functional low-frequency hearing was preserved in 13 out of 14 patients (93%).

CONCLUSIONS

The residual hearing preservation results in children were superior to the results previously reported in adults.

Dexamethasone delivery for hearing preservation in animal cochlear implant model: continuity, long-term release, and fast release rate

Background: Clinically, steroids have been used for hearing preservation both topically and systemically during cochlear implantation.Objective: This study compared steroid efficacy for hearing preservation among different types of delivery modes using an animal experiment.Materials and methods: For 76 guinea pigs, topical and systemic delivery methods, four pump types with different infusion rates, delivery durations, and total steroid amounts were used. Threshold changes of 8, 16, and 32 kHz after dummy electrode insertion were evaluated at 1 and 4 weeks and compared among delivery method and pump types. Inflammatory response in the cochlea was histologically compared.Results: For topical delivery groups, long-term release showed advantages in preserving hearing. Systemic delivery groups showed smaller threshold shifts than control group in all frequencies (p > .05). In short-term low dose application, compared to topical delivery, systemic delivery showed advantage in hearing preservation at both time point. However, others fail to show significant difference between two methods. Histologically, inflammatory response in the scala tympani at the basal turn was less in systemic delivery, especially in high dose and long-term.Conclusion and significance: The difference of hearing preservation was not obvious between two delivery methods. Higher dose and longer duration might have advantages in hearing preservation.

Anatomical Correlates and Surgical Considerations for Localized Therapeutic Hypothermia Application in Cochlear Implantation Surgery

Application of localized, mild therapeutic hypothermia during cochlear implantation (CI) surgery is feasible for residual hearing preservation.

Characterizing Insertion Pressure Profiles During Cochlear Implantation: Simultaneous Fluoroscopy and Intracochlear Pressure Measurements

BACKGROUND

Combined electrical-acoustical stimulation (EAS) has gained popularity as patients with residual hearing are increasingly undergoing cochlear implantation. Preservation of residual hearing correlates with hearing outcomes, but loss of hearing occurs in a subset of these patients. Several mechanisms have been proposed as causing this hearing loss; we have previously described high amplitude pressure transients, equivalent to high-level noise exposures, in the inner ear during electrode insertion. The source of these transients has not been identified.

METHODS

Cadaveric human heads were prepared with an extended facial recess. Fiber-optic pressure sensors were inserted into the scala vestibuli and scala tympani to measure intracochlear pressures. Two cochlear implant (CI) electrode styles (straight and perimodiolar) were inserted during time-synced intracochlear pressures and video fluoroscopy measurements.

RESULTS

CI electrode insertions produced pressure transients in the cochlea up to 160 to 170 dB pSPL equivalent for both styles, consistent with previous results. However, the position of the electrode within the cochlea when transients were generated differed (particularly contact with the medial or lateral walls).

CONCLUSIONS

These results begin to elucidate the insertion pressure profiles of CI electrodes, which can be used to improve CI electrode designs and facilitate "silent-insertions" to improve chances of hearing preservation.

Dynamic intracochlear pressure measurement during cochlear implant electrode insertion

Background: Electrode insertion into the cochlea can cause significant pressure changes inside the cochlea with assumed effects on the cochlea's functionality regarding residual hearing. Model-based intracochlear pressure (ICP) changes were performed statically at the cochlear helix. Aims/objectives: The aim of this study was to observe dynamic pressure measurements during electrode insertion directly at the cochlear implant electrode. Material and methods: The experiments were performed in an uncurled cochlear model that contained a volume value equivalent to a full cochlea. A microfibre pressure sensor was attached at one of two positions on a cochlear implant electrode and inserted under different insertional conditions. Results: We observed the ICP increase depending on the insertional depth. A sensor-position-specific pressure change is insertional-depth dependent. Interval insertion did not lead to a lower peak insertional ICP. Conclusions and significance: In contrast to the static pressure-sensor measurement in the artificial model's helix, a dynamic measurement directly at the electrode shows the pressure profile to increase based on the insertional depth. A mechanical traumatic relevance of the observed pressure values cannot be fully excluded.

The natural progression of low-frequency hearing loss in patients who meet hybrid implant system candidacy criteria

OBJECTIVES/HYPOTHESIS

To investigate the natural progression of hearing loss in patients with high-frequency hearing loss whose audiograms met the criteria for a hybrid cochlear implant (CI).

STUDY DESIGN

Retrospective database review.

METHODS

We retrospectively identified patients who met the criteria for a hybrid CI from our audiometric database. We also recorded the etiology of hearing loss in each patient and excluded patients with retrocochlear etiologies, those age <6 years, duration of observation <1 year, or those with a mixed or conductive hearing loss. We calculated the pre-CI progression of residual low-frequency (LF) hearing level in decibels per year and investigated the risk factor of the progression of hearing loss.

RESULTS

A total of 1,083 ears of 944 patients were included in this study. The average rate of hearing loss progression for all etiologies was 1.70 ± 0.10 dB/yr at an average of 250 Hz, 500 Hz, and 1 kHz in the affected ear(s). The progression of hearing loss was 5.0 ± 0.93 dB/yr in patients with Meniere's disease and 3.5 ± 0.76 dB/yr in those with autoimmune disease, both of which were significantly faster than progression rates in other etiologies. In patients with idiopathic, genetic/hereditary, and congenital hearing loss, the progression of hearing loss was 1.46 ± 0.10 dB/yr. Patients with steeply sloping hearing loss experienced significantly faster progression in the ipsilateral ear compared to patients with another audiometric type.

CONCLUSIONS

It is suggested that Meniere's disease, autoimmune-mediated inner ear disease, and steeply sloping hearing loss in the ipsilateral ear are risk factors for faster progression of residual LF hearing level.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:1299-1303, 2020.

Intracochlear Pressure Transients During Cochlear Implant Electrode Insertion: Effect of Micro-mechanical Control on Limiting Pressure Trauma

HYPOTHESIS

Use of micro-mechanical control during cochlear implant (CI) electrode insertion will result in reduced number and magnitude of pressure transients when compared with standard insertion by hand.

INTRODUCTION

With increasing focus on hearing preservation during CI surgery, atraumatic electrode insertion is of the utmost importance. It has been established that large intracochlear pressure spikes can be generated during the insertion of implant electrodes. Here, we examine the effect of using a micro-mechanical insertion control tool on pressure trauma exposures during implantation.

METHODS

Human cadaveric heads were surgically prepared with an extended facial recess. Electrodes from three manufacturers were placed both by using a micro-mechanical control tool and by hand. Insertions were performed at three different rates: 0.2 mm/s, 1.2 mm/s, and 2 mm/s (n = 20 each). Fiber-optic sensors measured pressures in scala vestibuli and tympani.

RESULTS

Electrode insertion produced pressure transients up to 174 dB SPL. ANOVA revealed that pressures were significantly lower when using the micro-mechanical control device compared with insertion by hand (p << 0.001). No difference was noted across electrode type or speed. Chi-square analysis showed a significantly lower proportion of insertions contained pressure spikes when the control system was used (p << 0.001).

CONCLUSION

Results confirm previous data that suggest CI electrode insertion can cause pressure transients with intensities similar to those elicited by high-level sounds. Results suggest that the use of a micro-mechanical insertion control system may mitigate trauma from pressure events, both by reducing the amplitude and the number of pressure spikes resulting from CI electrode insertion.

Electric and Acoustic Stimulation in Cochlear Implant Recipients with Hearing Preservation

Hearing loss affects 30 million people in the United States, and a subset of these patients have normal low-frequency hearing and ski-sloped high-frequency hearing loss. For these patients, hearing aids alone may not provide adequate benefit. Cochlear implantation alone has been utilized to improve speech perception. The addition of high-frequency electric hearing to low-frequency acoustic hearing in these patients is beneficial. Technical improvements have allowed preservation of low-frequency hearing in cochlear implant recipients, allowing for electric and acoustic stimulation in the same ear with significant improvements in speech perception, sound localization, music appreciation, and quality of life.

An Optimized Robot-Based Technique for Cochlear Implantation to Reduce Array Insertion Trauma

OBJECTIVE

To compare the intracochlear trauma induced by optimized robot-based and manual techniques with a straight electrode array prototype inserted at different lengths.

STUDY DESIGN

Experimental study.

SETTING

Robot-based otologic surgery laboratory.

SUBJECTS AND METHODS

A prototype array was inserted at different insertion lengths (21 and 25 mm) in 20 temporal bones. The manual insertion was performed with a microforceps. The optimized approach consisted of an optimal axis insertion provided by a robot-based arm controlled by a tracking system, with a constant speed of insertion (0.25 mm/s) achieved by a motorized insertion tool. The electrode position was determined at the level of each electrode by stereomicroscopic cochlea section analysis.

RESULTS

A higher number of electrodes correctly located in the scala tympani was associated with the optimized approach ( P = .03, 2-way analysis of variance). Regardless of the insertion technique used, the array inserted at 25 mm allowed complete insertion of the active stimulating portion of the array in all cases. Insertion depth was greater when the array was inserted to 25 mm versus 21 mm ( P < .001, 2-way analysis of variance). The optimized insertion was associated with less trauma than that from manual insertion regardless the length of the inserted array ( P = .04, 2-way analysis of variance).

CONCLUSION

Compared with a manual insertion, intracochlear trauma could be reduced with array insertion performed on an optimal axis by using motorized insertion and by applying a constant insertion speed.