Impact of Routine Plain X-ray on Postoperative Management in Cochlear Implantation

Intraoperative Handheld Digital X-ray for Assessment of Intracochlear Positioning of Electrode Arrays in Recipients of Cochlear Implants

Objectives: This study aims to evaluate the practicality of handheld digital X-ray in determining the position of the electrode array following Cochlear implantation (CI). Methods: A retrospective study was conducted involving 11 patients (12 ears) who underwent intraoperative imaging via handheld X-ray (MINE ALNU®, OTOM, Gwangju, South Korea) post-CI between December 2021 and January 2023. Immediate confirmation of the correct electrode array placement in the cochlea was achieved, with subsequent comparisons made to C-arm image and postoperative transorbital view X-ray. Results: Rapid intraoperative imaging was achieved in all instances. The electrode types used included 9 Nucleus slim modiolar electrodes, 1 Nucleus contour electrode, and 2 Medel flex26 electrodes. A malpositioned electrode array was detected in one patient. The handheld digital X-ray also adeptly visualized the electrodes implanted in pediatric patients. Conclusions: The use of intraoperative handheld digital X-ray using MINE ALNU® proves to be a safe, efficient, straightforward, and reliable method for immediate identification of an inserted electrode array. It has potential to replace the traditional C-arm X-ray for verifying electrode positioning in the operating room.

The case for intra-operative X-ray in cochlear implantation: Four illustrative cases and literature review

OBJECTIVES

To demonstrate the utility of routine intraoperative plain film imaging in optimizing outcomes in cochlear implantation.

INTRODUCTION

Evolving surgical techniques, programming, and electrode arrays have all improved performance outcomes in cochlear implantation. Yet despite decreasing complication rates, electrode misplacement remains a common occurrence. Utilization of intraoperative confirmational tools (radiologic, electrophysiologic) remains unstandardized despite the acknowledged importance of proper electrode positioning. The purpose of this article is to illustrate the use and benefits of intraoperative X-ray (IOXR) in four cases, particularly in cases of normal electrophysiologic testing.

METHODS

Four cases performed by an experienced CI surgeon are discussed where electrode malposition was only detected through X-ray. Literature review was performed on the use of intraoperative imaging, focusing on plain film radiography.

RESULTS

Case 1-3 describe examples of resistance-free electrode insertion in patients with normal pre-operative imaging. Intraoperative impedances and neural response telemetry (NRT) were normal. However, IOXR ultimately revealed tip fold-over prompting array repositioning. Case 4 describes an elective replacement of a soft-failing device. Resistance was encountered during array insertion, with IOXR demonstrating incomplete insertion compared with prior imaging. Positioning was revised to achieve pre-revision insertion depth, demonstrating the utility of prior IOXR in revision cases. Literature review of IOXR is discussed.

CONCLUSION

Appropriate placement of the electrode is paramount to successful CI outcomes. These cases illustrate IOXR as a safe, effective method to ensure optimal placement even in cases of normal electrophysiologic testing, supporting its routine use even by the most seasoned surgeons.

Misplaced Cochlear Implant Electrodes Outside the Cochlea: A Literature Review and Presentation of Radiological and Electrophysiological Findings

HYPOTHESIS

It is possible to detect when misplacement and malposition of the cochlear implant (CI) electrode array has occurred intraoperatively through different investigations. We aim to explore the literature surrounding cochlear implant misplacements and share our personal experience with such cases to formulate a quick-reference guide that may be able to help cochlear implant teams detect misplacements early.

BACKGROUND

Misplacement and malposition of a cochlear implant array can lead to poor hearing outcomes. Where misplacements go undetected during the primary surgery, patients may undergo further surgery to replace the implant array into the correct intracochlear position.

METHODS

Systematic literature review on cochlear implant misplacements and malpositions and a retrospective review of our program's cases in over 6,000 CI procedures.

RESULTS

Twenty-nine cases of CI misplacements are reported in the English literature. Sixteen cases of cochlear implant misplacements are reported from our institution with a rate of 0.28%. A further 12 cases of intracochlear malpositions are presented. The electrophysiological (CI electrically evoked auditory brainstem response, transimpedance matrix) and radiological (X-ray and computed tomography scan) findings from our experience are displayed in a tabulated quick-reference guide to show the possible characteristics of misplaced and malpositioned cochlear implant electrode arrays.

CONCLUSION

Both intraoperative electrophysiological and radiological tests can show when the array has been misplaced or if there is an intracochlear malposition, to prompt timely intra-operative reinsertion to yield better outcomes for patients.

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.

Robotic Milling of Electrode Lead Channels During Cochlear Implantation in an ex-vivo Model

Objective: Robotic cochlear implantation is an emerging surgical technique for patients with sensorineural hearing loss. Access to the middle and inner ear is provided through a small-diameter hole created by a robotic drilling process without a mastoidectomy. Using the same image-guided robotic system, we propose an electrode lead management technique using robotic milling that replaces the standard process of stowing excess electrode lead in the mastoidectomy cavity. Before accessing the middle ear, an electrode channel is milled robotically based on intraoperative planning. The goal is to further standardize cochlear implantation, minimize the risk of iatrogenic intracochlear damage, and to create optimal conditions for a long implant life through protection from external trauma and immobilization in a slight press fit to prevent mechanical fatigue and electrode migrations.

Methods: The proposed workflow was executed on 12 ex-vivo temporal bones and evaluated for safety and efficacy. For safety, the difference between planned and resulting channels were measured postoperatively in micro-computed tomography, and the length outside the planned safety margin of 1.0 mm was determined. For efficacy, the channel width and depth were measured to assess the press fit immobilization and the protection from external trauma, respectively.

Results: All 12 cases were completed with successful electrode fixations after cochlear insertions. The milled channels stayed within the planned safety margins and the probability of their violation was lower than one in 10,000 patients. Maximal deviations in lateral and depth directions of 0.35 and 0.29 mm were measured, respectively. The channels could be milled with a width that immobilized the electrode leads. The average channel depth was 2.20 mm, while the planned channel depth was 2.30 mm. The shallowest channel depth was 1.82 mm, still deep enough to contain the full 1.30 mm diameter of the electrode used for the experiments.

Conclusion: This study proposes a robotic electrode lead management and fixation technique and verified its safety and efficacy in an ex-vivo study. The method of image-guided robotic bone removal presented here with average errors of 0.2 mm and maximal errors below 0.5 mm could be used for a variety of other otologic surgical procedures.

The Modified Stenver's View for Cochlear Implants - What do the Surgeons Want to Know?

Despite developments in electrophysiological testing, imaging remains the standard method to determine cochlear implant positioning. Whilst cone beam computed tomography is optimal, modified Stenver radiographs are easier to perform and are therefore commonly used. With recent debate as to the need for routine imaging in uncomplicated cases, the radiologist is increasingly faced with cases of abnormal anatomy or surgical error.

The primary interest is the positioning of the electrode array within the cochlea. This includes evidence of tip roll over or kinking and depth of electrode insertion, as both are independent predictors of hearing outcomes and may necessitate revision surgery.

Reliability of Measuring Insertion Depth in Cochlear Implanted Infants and Children Using Cochlear View Radiography

OBJECTIVES

Cochlear implant depth of insertion affects audiologic outcomes and can be measured in adults using plain films obtained in the "cochlear view." The objective of this study was to assess interrater and intrarater reliability of measuring depth of insertion using cochlear view radiography.

STUDY DESIGN

Prospective, observational.

SETTING

Tertiary referral pediatric hospital.

SUBJECTS AND METHODS

Patients aged 11 months to 20 years (median, 4 years; interquartile range [IQR], 1-8 years) undergoing cochlear implantation at our institution were studied over 1 year. Children underwent cochlear view imaging on postoperative day 1. Films were deidentified and 1 image per ear was selected. Two cochlear implant surgeons and 2 radiologists evaluated each image and determined angular depth of insertion. Images were re-reviewed 6 weeks later by all raters. Inter- and intrarater reliability were calculated with intraclass correlation coefficients (ICCs).

RESULTS

Fifty-seven ears were imaged from 42 children. Forty-nine ears (86%) had successful cochlear view x-rays. Median angular depth of insertion was 381° (minimum, 272°; maximum, 450°; IQR, 360°-395°) during the first round of measurement. Measurements of the same images reviewed 6 weeks later showed median depth of insertion of 382° (minimum, 272°; maximum, 449°; IQR, 360°-397°). Interrater and intrarater reliability ICCs ranged between 0.81 and 0.96, indicating excellent reliability.

CONCLUSIONS

Postoperative cochlear view radiography is a reliable tool for measurement of cochlear implant depth of insertion in infants and children. Further studies are needed to determine reliability of intraoperatively obtained cochlear view radiographs in this population.