Prevalence and complications of MRI scans of cochlear implant patients: English version

Brazilian Society of Otology task force - cochlear implant ‒ recommendations based on strength of evidence

OBJECTIVE

To make evidence-based recommendations for the indications and complications of Cochlear Implant (CI) surgery in adults and children.

METHODS

Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on cochlear implantation were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions.

RESULTS

The topics were divided into 2 parts: (1) Evaluation of candidate patients and indications for CI surgery; (2) CI surgery - techniques and complications.

CONCLUSIONS

CI is a safe device for auditory rehabilitation of patients with severe-to-profound hearing loss. In recent years, indications for unilateral hearing loss and vestibular schwannoma have been expanded, with encouraging results. However, for a successful surgery, commitment of family members and patients in the hearing rehabilitation process is essential.

Multi-Magnet Cochlear Implant Technology and Magnetic Resonance Imaging: The Safety Issue

Despite the spread of novel-generation cochlear-implant (CI) magnetic systems, access to magnetic resonance imaging (MRI) for CI recipients is still limited due to safety concerns. The aim of this study is to assess and record the experiences of Hires Ultra 3D (Advanced Bionics) recipients who underwent an MRI examination. A multicentric European survey about this topic was conducted focusing on safety issues, and the results were compared with the current literature. We collected a total of 65 MRI scans performed in 9 otologic referral centers for a total of 47 Hires Ultra 3D recipients, including, for the first time, 2 children and 3 teenagers. Preventive measures were represented by scanning time and sedation for children. Head wrapping was used in eight cases, and six of the eight cases received local anesthesia, even if both measures were not needed. Only three patients complained of pain (3/65 examinations, 4.6%) due to the tight head bandage, and one of the three cases required MRI scan interruption. No other adverse events were reported. We believe that these results should encourage MRI execution in accordance with manufacturer recommendations for Ultra 3D recipients.

A Systematic Review of Cochlear Implant-Related Magnetic Resonance Imaging Artifact: Implications for Clinical Imaging

OBJECTIVE

To conduct a systematic review of the existing literature with the aim of evaluating and consolidating the present understanding of strategies for mitigating magnetic resonance imaging (MRI) artifacts related to cochlear implants in adult and pediatric patients, covering both in-vivo and ex-vivo investigations.

DATA SOURCES

A systematic review of MEDLINE-Ovid, Embase, Google Scholar, The Cochrane Library, and Scopus was performed from inception through April 2022. The protocol was registered with PROSPERO before commencement of data collection (CRD CRD42022319651).

REVIEW METHODS

The data were screened and collected by two authors independently, and eligibility was assessed according to Cochrane Handbook and Preferred Reporting Items for Systematic Review and Meta-Analysis recommendations, whereas the quality of the articles was evaluated using the NIH Study Quality Assessment.

RESULTS

The search yielded 2,354 potentially relevant articles, of which 27 studies were included in the final review. Twelve studies looked at 1.5-T MRI, four studies looked at 3-T MRI, eight studies looked at both 1.5 and 3 T, one study looked at 0.2 and 1.5 T, and one study looked at 3- and 7.0-T MRI. Nineteen studies focused on MRI sequences as a means of artifact reduction, nine studies focused on implant magnet positioning, two studies focused on head positioning, and one study focused on both magnet and head positioning. In terms of MRI sequences, diffusion-weighted imaging produced larger artifacts compared with other sequences, whereas fast spin echo/turbo spin echo sequences and fat suppression techniques produced smaller artifacts. The position of the magnet was also found to be important, with a magnet position more than 6.5 cm posterior to the external auditory canal producing the best images with the least distortion. The angle at which the magnet is placed also affects visibility of different brain structures.

CONCLUSION

Proper head positioning, magnet placement at a distance of over 6.5 cm from the external auditory canal, use of spin echo sequences, and fat suppression techniques reduce the size and shape of MRI artifacts.

Prospective study on magnetic resonance imaging in cochlear implant patients

PURPOSE

Monocentric, prospective study to investigate whether concomitant support of cochlear implant (CI) patients by CI-trained otolaryngologists and application of a standardized head bandage can minimize potential complications during magnetic resonance imaging (MRI).

METHODS

Thirty-seven patients with 46 CIs underwent MRI with a prophylactic head bandage. All participants and the otolaryngologist at the CI center completed pre- and post-MRI questionnaires documenting body region scanned, duration of MRI and bandage wear, field strength during the scan, and any complications. If pain was experienced, it was assessed using a visual analog scale (1-10).

RESULTS

MRI was performed without adverse events in 37.8% of cases. Magnet dislocation requiring surgical revision occurred in 2% of cases. Pain was reported in 86% of cases, often due to the tightness of the dressing. Patients with rotating, MRI-compatible magnets reported significantly less pain than participants with older-generation implants. In 11% of cases, the MRI was discontinued.

CONCLUSION

Serious complications during MRI in cochlear implant patients are rare. Pain is the most common adverse event, probably mainly due to the tight bandage required by most implant types. With newer generations of magnets, these patients experience less pain, no dislocation of the magnets, and no need for bandaging. Although magnet dislocation cannot be completely prevented in older generations of implants, it appears to be reduced by good patient management, which recommends examination under the guidance of physicians trained in the use of hearing implants.

Magnetic Resonance Imaging with Active Implantable Hearing Devices: Reports from the Daily Radiological Routine in an Outpatient MR Center

PURPOSE

For people with hearing implants (HI), magnetic resonance imaging (MRI) still presents some difficulties due to the built-in magnet. Radiologists often have concerns regarding complications associated with HIs. The aim of this study was to record the experiences of HI users during and after MRI examinations.

METHOD

A survey including 15 questions regarding MRI specifics, namely changes in hearing ability, hearing/sound impressions, pain, uncomfortable feelings, etc., were mailed to our patients.

RESULTS

Overall, 79 patients with HI had a total of 159 MR examinations in our institute. A total of 45 HI recipients reported back: 35% stated that they had been rejected by an MRI Institute because of their HI. Their feelings/impression ratings during the measurements were not present and therefore were not rated for the majority (49%), 42% of the HI users rated the pain with 0 (no pain), 2% with 1 (very light pain), 4% with 5 (acceptable pain), and 2% rated the pain with 7, which is between acceptable and strong pain. One examination resulted in a dislocation of the magnet of a cochlear implant (CI 512 Cochlear Limited). No adverse events were reported for MED-EL HI users in the survey (none of the contacted AB users answered the questionnaire). The reported mean daily wearing time was 11.6 ± 4.6 h per day for 6.3 ± 1.7 days per week.

CONCLUSIONS

Based on these results and our experience we conclude that MRI examinations with HI are safe given that the measurements are performed according to the safety policies and procedures released by the manufacturers.

Patient Preferences for Long-Term Implant Care in Cochlear, Glaucoma and Cardiovascular Diseases

In the process of developing and implementing innovative implant technologies the consideration of patient preferences can be beneficial for patients, doctors and developers. Nevertheless, in existing literature, there is still scarce knowledge of patients' perspectives on long-term implant care. In this study, three discrete choice experiments (DCEs) were conducted in the context of cochlear implants (CI, n = 92), glaucoma implants (GI, n = 21) and cardiovascular implants (CVI, n = 23), examining the relative importance of attributes of long-term implant care from the patients' perspective. The participants chose between differently shaped options for implant-related care. The attributes of these care options were generated and selected based on previous literature reviews, group discussions and a diary study with patients. The choice data were analyzed via binary logit regression. In CI-DCE, the technological compatibility of the implant with newer implant models, accessories or devices from other manufacturers was highly valued by participants, whereas in GI-DCE the (in)dependency on glaucoma medication post-implantation had the greatest influence on participants' choice behavior. In CVI-DCE, the attribute with the highest relative importance related to the means of securing long-term treatment success. In all three DCE, shared decision making was relatively important for participants. Our results emphasized the importance of an adequate transfer of technological advancements in implant care for promoting patient benefits, such as the availability of comprehensible, understandable, high-quality information about current developments. Similarly, promoting technological health literacy and further pushing the technological compatibility, durability and safety of implants are directions for future implant development in accordance with patients' preferences. Therefore, the participation of implant wearers in the development process is encouraged.

Risk of magnetic resonance imaging-induced magnet dislocation for different types of cochlear implants: a single-center retrospective study

BACKGROUND

When performing magnetic resonance imaging (MRI) in patients with a cochlear implant (CI), complication rates vary widely in the literature. The primary objective of this retrospective study was to determine the prevalence of complications, in particular magnet dislocation, in patients with CI undergoing 1.5 Tesla (T) MRI. As a secondary objective, the prevalence of magnet dislocation for specific cochlear implant device types was elaborated.

METHODS

In a single-center retrospective study, all patients with a cochlear implant presenting for an MRI examination at 1.5 T at our institution between January 1st, 2010 and December 31st, 2020 were included. Implants with axial and diametrical magnets were included in the study. MRI safety measures were applied before imaging. The prevalence of complications was evaluated. Magnet dislocation rates were calculated for device types with at least 20 MRI exposures.

RESULTS

During the study period, 196 MRI examinations were performed in a total of 128 patients, accounting for 149 different implants (21 implanted bilaterally) with a total of 231 implant exposures to MRI (average 1.69 ± 1.57; min. 1, max. 12). Complications were reported in 50 out of 231 cochlear implant exposures (21.6%). Magnet dislocation occurred in a total of 27 cases (11.7%). Dislocation rates were 29.6% for the Cochlear® CI500 series (24 dislocations from 81 exposures), 1.1% for the Cochlear® CI24RE series (1 from 87) and 0% for the MED-EL® Synchrony (0 from 36). The dislocation rate for the CI500 was significantly higher than for the CI24RE (χ²₍₁₎ = 26.86; p < 0.001; ϕ = 0.40) or the Synchrony (χ²₍₁₎ = 13.42; p < 0.001; ϕ = 0.34).

CONCLUSIONS

For 1.5 T MRI, the risk of magnet dislocation ranges from 0 to 29.6% and depends on the CI device type. Implants with a diametrical magnet can be considered potentially MRI-safe, whereas in CIs with axial magnets, the CI500 is at high risk of magnet dislocation. Therefore, apart from a strict indication for an MRI and adherence to safety protocols, post-MRI follow-up examination to rule out magnet dislocation is recommended.

The experience of auditory implant recipients undergoing magnetic resonance imaging: Factors associated with pain

OBJECTIVE

Many patients with cochlear implants (CI) and auditory brainstem implants (ABI) require magnetic resonance imaging (MRI) following implantation. This study explores the patient experience of MRI, identifying factors associated with pain, and the effect of interventions designed to enhance comfort and safety.

METHODS

A prospective observational case series from a tertiary referral unit. Tight head bandaging ± local anaesthetic injection (devices with non-MRI-compatible magnets) or observation alone (implants with MRI-compatible magnets) were employed for 1.5 T MRI of consecutive adult patients with CI or ABI without magnet removal. Pain was recorded via visual analogue scale (1 = no pain, 5 = extreme pain) at three time points; (1) baseline, (2) head bandage applied (3) during scanning. Patient age, device type, body area imaged and total scan time were recorded as variables, alongside adverse events.

RESULTS

Data were collected for 227 MRI scans (34 patients with ABI, 32 with CI). In patients managed with bandaging, pain score after bandaging but prior to scanning (median 2.2) did not differ from pain during scanning (2.1), but both were significantly higher than baseline (1.4, both P ≤ 0.001). Scanning areas other than the head/cervical spine was associated with higher pain scores (P = 0.036). Pain during MRI differed between different manufacturers implants (P ≤ 0.001). Adverse events occurred in 8/227 scans (3.5%), none occurring with devices containing an MRI-compatible magnet.

CONCLUSION

MRI scanning with auditory implant magnets in situ is safe and well tolerated by patients.

Characterizing Cochlear Implant Magnet-Related MRI Artifact

OBJECTIVE

To evaluate cochlear implant (CI) magnet-related MRI artifact shape and size, as well as imaging indications and clinical adequacy of scans.

METHODS

A retrospective chart review was performed for patients undergoing CI and subsequent MRI head imaging from 2014 to 2020 at a single institution. Indications and adequacy of each scan was recorded, and interpretability compared by indication. Magnet-related artifact size was determined by performing ellipsoid modeling at axial slice of greatest signal loss. Artifact radius in centimeters was calculated for 5 sequence categories, and size compared between sequences, manufacturers, and by time from implantation.

RESULTS

Twenty patients underwent 58 head MRI scans. Approximately 76% of MRIs (n = 44) for 70% of patients (n = 14) were performed for indications known of prior to implantation; the remainder were performed during workup of new issues. Desired structures were interpretable in 23 (52%) of known-indication MRIs and 8 (57%) of new-indication MRIs, without significant difference (P = .751). Magnet-related artifact magnitude, compared to the reference T1-weighted fast spin echo (FSE) (4.47 cm), was similar in T2 FSE (4.57 cm, P = .068) and T1 gradient echo (GRE) sequences (4.79 cm, P = .28), but significantly greater in T2 GRE (6.86, P < .0001) and DWI (7.56 cm, P < .0001) sequences.

CONCLUSIONS

DWI and T2 GRE sequences are less useful in MRI evaluation of CI patients. With a more favorable artifact profile, T1 FSE, T2 FSE, and T1 GRE sequences more likely yield clinically useful information. The large proportion of scans performed for known pathology represents an opportunity to optimize for magnet location preoperatively.

Comparison of artefact reduction possibilities with the new active transcutaneous bone conduction implant (Bonebridge)

OBJECTIVE

This study aimed to evaluate the possibilities of artefact reduction using different anatomical implant positions with the Bonebridge bone-conduction hearing implant 602 for a patient with an acoustic neuroma requiring regular diagnostic magnetic resonance imaging of the tumour position.

METHOD

Three implant positions and magnetic resonance imaging examinations with and without customised sequences for metal artefact suppression were investigated. The diagnostic usefulness was rated by a radiologist (qualitative evaluation), and the relation between the area of artefact and the total head area was calculated (quantitative evaluation).

RESULTS

Following the qualitative analysis, the radiologist rated the superior to middle fossa implant placement significantly better for diagnostic purposes, which is in agreement with the calculated artefact ratio (p < 0.0001). The customised slice-encoding metal artifact correction view-angle tilting metal artifact reduction technique sequences significantly decreased the relative artefact area between 5.13 per cent and 25.02 per cent. The smallest mean artefact diameter was found for the superior to middle fossa position with 6.80 ± 1.30 cm (range: 5.42-9.74 cm; reduction of 18.65 per cent).

CONCLUSION

The application of artefact reduction sequencing and special anatomical implant positioning allows regular magnetic resonance imaging in patients with the bone-conduction hearing implant 602 without sacrificing diagnostic imaging quality for tumour diagnosis.

Prospective Evaluation of 3 T MRI Effect on Residual Hearing Function of Cochlea Implantees

Introduction: The approval process for MRI safety of implants includes physical observations and an experimental evaluation in artificial settings to simulate the in vivo effect. This contains the observation of temperature changes and artificial current generation by the magnetic field. From these findings, the safety of an implant and its effect on the patient can be estimated. MRI safety is based on an in vivo evaluation of adverse events after the approval process, but an actual analysis of the effect on different tissues is not followed. The effect of MRI scanning in cochlea implantees on their residual hearing as the correlate of the hair cell function is so far unknown, therefore the aim of the present study was to observe the effect of 3 T MRI on the residual hearing of cochlea implantees. Material and Methods: In this prospective study, we performed a 3 T MRI T2 2D MS Drive sequence in eight cochlea-implanted ears. Before and after the MRI scan, a bone conduction pure tone audiogram (BC PTA) was performed. All cochlea implantees had a pre-scanning threshold of low frequency residual hearing between 20 dB and 65 dB. Results: Low frequency mean residual hearing was not affected by the 3 T T2 2D MS Drive sequence. We observed a pre-scanning threshold at 250 Hz of 42.9 (SD 3.9) dB and for 500 Hz 57.1 (SD 6.4) dB. Post-scanning BC PTA was for 250 Hz 42.1 (SD 3.9) dB and for 500 Hz 57.1 (SD 5.7) dB. Conclusion: 3 T MRI scanning has no significant functional effect on the hair cells in cochlea implantees in low frequencies with a T2 2D MS Drive sequence.

A global survey of healthcare professionals undertaking MRI of patients with cochlear implants: a heterogeneity of practice and opinions

OBJECTIVE

To capture practice and opinions around the current clinical use of MRI in patients with cochlear implants (CIs), and to characterise patient progression from referral to image reporting.

METHODS

An online survey recruited 237 healthcare professionals between 9 December 2019 and 9 September 2020. Descriptive statistics and informal thematic analyses were conducted.

RESULTS

Respondents estimated that approximately 75% of CI users referred for an MRI proceeded to image acquisition, of which ~70% of cases comprised image acquisition on the head and the remaining cases on another area. They estimated that the proportion of these images that were usable was 93 and 99%, respectively. Confidence in most processes was high, with at least two-thirds of respondents reporting to be very or somewhat confident in obtaining consent and acquiring images. Conversely, fewer than half the respondents had the same confidence when splinting and bandaging the implant and troubleshooting any issues arising. Patient safety was rated of paramount importance, with patient comfort a clear second and image quality third.

CONCLUSION

These findings highlight the need for consistent publication of clear, succinct, and standardised operating procedures for scanning patients with CIs and the requirement for regular training of radiographic and radiological healthcare professionals to address the heterogeneity of devices available.

ADVANCES IN KNOWLEDGE

There is a need to improve the communication to radiography and radiology personnel regarding the nature of CIs, the heterogeneity of devices in existence, and the key differences between them. CI users risk being underserved by diagnostic medical imaging.

Neuroplasticity following cochlear implants

The auditory cortex of people with sensorineural hearing loss can be re-afferented using a cochlear implant (CI): a neural prosthesis that bypasses the damaged cells in the cochlea to directly stimulate the auditory nerve. Although CIs are the most successful neural prosthesis to date, some CI users still do not achieve satisfactory outcomes using these devices. To explain variability in outcomes, clinicians and researchers have increasingly focused their attention on neuroscientific investigations that examined how the auditory cortices respond to the electric signals that originate from the CI. This chapter provides an overview of the literature that examined how the auditory cortex changes its functional properties in response to inputs from the CI, in animal models and in humans. We focus first on the basic responses to sounds delivered through electrical hearing and, next, we examine the integrity of two fundamental aspects of the auditory system: tonotopy and processing of binaural cues. When addressing the effects of CIs in humans, we also consider speech-evoked responses. We conclude by discussing to what extent this neuroscientific literature can contribute to clinical practices and help to overcome variability in outcomes.

Diagnosing complications following cochlear implantation using transcutaneous ultrasound

Purpose

The aim of this study was to investigate the feasibility and reliability of transcutaneous ultrasound for the detection of complications after cochlear implantation.

Methods

In a single center retrospective cohort study, 115 consecutive cases of suspected complications after cochlear implantation (intervention group) were examined. The rate of pathologic ultrasound findings for specific leading symptoms and diagnoses was compared to a control group comprising twenty consecutive cochlear implants in symptom-free patients.

Results

Diagnostic ultrasound showed distinctly more pathologic findings in the intervention group (n = 67; 58.3%; p < 0.001) compared to the control group (n = 1; 5%). Ultrasound revealed significantly more pathologic findings in haematoma or seroma around the implant (n = 17; 100%; p < 0.001; ϕ = 0.94) and magnet dislocation (n = 44; 97.7%; p < 0.001; ϕ = 0.92) confirmed by a strong effect. Ultrasound examination showed a medium to high effect size in patients presenting with local infections (n = 3; 21.4%; p = 0.283; ϕ = 0.25) and skin flap oedema (n = 2; 50%; p = 0.061; ϕ = 0.51). In contrast, ultrasound examinations displayed a low effect size in undefined cephalgia (0%; p = 0.444; ϕ = 0.17) and device malfunction or failure (0%; p > 0.999; ϕ = 0.13).

Conclusion

Transcutaneous ultrasound can be advocated as a feasible and effective method in the diagnostic work-up of magnet dislocation and haematoma or seroma around the implant following cochlear implantation. Contrary, ultrasound findings can be expected to be inconspicuous in patients presenting with undefined cephalgia and device malfunction or failure.

Magnetic Resonance Imaging in Patients With Hearing Implants - Follow-up on Prevalence and Complications

OBJECTIVE

To examine the number of magnetic resonance imaging (MRI) examinations performed in patients with hearing implants and to quantify side effects or complications related to this procedure.

STUDY DESIGN

Questionnaire.

SETTING

Tertiary referral center, academic hospital.

PATIENTS

One thousand four hundred sixty-onepatients with an implanted hearing system.

INTERVENTION

Patients were asked to complete a questionnaire either during a visit to the clinic (304) or by mail contact (1,157) between February 2018 and March 2019.

MAIN OUTCOME MEASURES

Number of examinations by means of MRI per patient and number of side effects or complications.

RESULTS

A total of 711 questionnaires were returned. After excluding nonvalid information on the questionnaire, 12.8% of patients were identified who had undergone an MRI after having received their hearing implant. Within this group of 91 patients, the most common precaution undertaken was a head bandage (69%). Side effects were mainly pain (37%), followed by anxiety (15%) and tinnitus (9%). The MRI had to be aborted in 14% and dislocation of the magnet occurred in 7% of examinations.

CONCLUSIONS

Our data indicate that patients undergoing hearing implant surgery need better information about the limitations and requirements of MRI. The occurrence of side effects is likely as only half of the patients in our study group were completely free of symptoms. Dislocation of the implant magnet was observed in several cases, hence patients and physicians need to be educated about this potential complication.

Cochlear implant user perceptions of magnetic resonance imaging

OBJECTIVES

To characterise opinions about needing to undergo MRI within the population of current cochlear implant (CI) users.

BACKGROUND

Magnetic resonance imaging (MRI) of CI users is often associated with severe discomfort and magnet displacement.

METHODS

A global online survey of 310 CI users was conducted between 22nd July and 13th September 2020.

RESULTS

Only 55% of respondents had been told whether their model of CI could undergo MRI. 31% of respondents considered MRI when deciding whether to receive a CI, and 28% when deciding which CI model to have. 64% reported concerns related to their CI if needing MRI compared to 29% reporting concerns unrelated to their CI. Willingness to undergo MRI reduced when considering magnet removal, splinting, bandaging, local anaesthesia, lasting discomfort, an inability to use their CI, or a reduction in image quality because of their CI. The single most influential factor was the possibility of damaging their CI (63%). 59% of respondents would consider minor surgery to upgrade their retaining magnet to one of a rotating design.

DISCUSSION

These findings highlight the heterogeneity of CI users' opinions about MRI.

CONCLUSION

We suggest several opportunities for improving the dissemination of current and accurate MRI-related information for CI users.

Ultrasound-Controlled Manual Magnet Repositioning in Magnet Dislocation of Cochlear Implants

OBJECTIVE

To investigate whether ultrasound is a helpful and reliable diagnostic tool to survey the status of the magnet previous and after manual repositioning in patients with partially dislocated cochlear implant (CI) magnets and to assess the success rate of a manual repositioning maneuver.

DESIGN

A prospective cohort study.

SETTING

A tertiary referral medical center.

PATIENTS

Patients with a cochlear implant who presented with magnet dislocation after magnetic resonance imaging (MRI) between June 1, 2019 and July 15, 2020.

INTERVENTIONS

Manual repositioning of the partially dislocated CI magnet surveyed by pre- and post-interventional ultrasound.

MAIN OUTCOME MEASURES

Rate of successfully diagnosed and manually repositioned magnets; complication rate and recurrence rate after initial manual repositioning maneuver.

RESULTS

Nine patients presented with a partial magnet dislocation diagnosed by pre-interventional ultrasound following MRI (n = 9 magnets; three ♀; eight right-sided implants; 65.4 ± 21.7 yr). All magnets were repositioned manually. The magnets were successfully repositioned at the first attempt in six out of eight patients. Two patients required a second and one patient a third attempt of manual repositioning. Post-interventional ultrasound confirmed the entirely restored magnet position in all cases. During the mean follow-up period of 7.3 months (±5.4 mo) no patient experienced any complication or recurrent dislocation of the respective magnet.

CONCLUSION

Manual magnet repositioning is a feasible and reliable method with a high success rate for partially dislocated CI magnets. The pre-interventional diagnosis as well as the post-interventional confirmation of the magnet status can be effectively determined by ultrasound. Thus, manual magnet repositioning and ultrasound investigation can be advocated as first-line therapeutic and diagnostic instruments when dealing with partial magnet dislocation.

Two-phase survey on the frequency of use and safety of MRI for hearing implant recipients

PURPOSE

Magnetic resonance imaging (MRI) is often used to visualize and diagnose soft tissues. Hearing implant (HI) recipients are likely to require at least one MRI scan during their lifetime. However, the MRI scanner can interact with the implant magnet, resulting in complications for the HI recipient. This survey, which was conducted in two phases, aimed to evaluate the safety and performance of MRI scans for individuals with a HI manufactured by MED-EL (MED-EL GmbH, Innsbruck, Austria).

METHODS

A survey was developed and distributed in two phases to HEARRING clinics to obtain information about the use of MRI for recipients of MED-EL devices. Phase 1 focused on how often MRI is used in diagnostic imaging of the head region of the cochlear implant (CI) recipients. Phase 2 collected safety information about MRI scans performed on HI recipients.

RESULTS

106 of the 126 MRI scans reported in this survey were performed at a field strength of 1.5 T, on HI recipients who wore the SYNCHRONY CI or SYNCHRONY ABI. The head and spine were the most frequently imaged regions. 123 of the 126 scans were performed without any complications; two HI recipients experienced discomfort/pain. One recipient required reimplantation after an MRI was performed using a scanner that had not been approved for that implant. There was only one case that required surgical removal of the implant to reduce the imaging artefact.

CONCLUSION

Individuals with either a SYNCHRONY CI or SYNCHRONY ABI from MED-EL can safely undergo a 1.5 T MRI when it is performed according to the manufacturer's safety policies and procedures.

Cochlear Implant Magnet Dislocation: Simulations and Measurements of Force and Torque at 1.5T Magnetic Resonance Imaging

OBJECTIVES

Dislocation of the magnet inside the implanted component of a cochlear implant (CI) can be a serious risk for patients undergoing a magnetic resonance imaging (MRI) exam. CI manufacturers aim to reduce this risk either via the design of the implant magnet or magnet housing, or by advising a compression bandage and cover over the magnet. The aim of this study is to measure forces and torque on the magnet for different CI models and assess the effectiveness of the design and preventative measures on the probability of magnet dislocation.

DESIGN

Six CI models from four manufacturers covering all the current CI brands were included. Each model was positioned on a polystyrene head with compression bandage and magnet cover according to the recommendations of the manufacturer and tested for dislocation in a 1.5T whole-body MRI system. In addition, measurements of the displacement force in front of the MRI scanner and torque at the MRI scanner isocenter were obtained.

RESULTS

Chance of CI magnet dislocation was observed for two CI models. The design of the magnet or magnet housing of the other models proved sufficient to prevent displacement of the magnet. The main cause for magnet dislocation was found to be the rotational force resulting from the torque experienced inside the magnet bore, which ranges from 2.4 to 16.2 N between the models, with the displacement force being lower, ranging from 1.0 to 1.8 N.

CONCLUSIONS

In vitro testing shows that two CI models are prone to the risk of magnet dislocation. In these CI models, preparation before MRI with special compression bandage and a stiff cover are of importance. But these do not eliminate the risk of pain and dislocation requiring patient consulting before an MRI exam. Newer models show a better design resulting in a significantly reduced risk of magnet dislocation.

Magnet dislocation following magnetic resonance imaging in cochlear implant users: Diagnostic pathways and managment

OBJECTIVES

Although modern cochlear implants (CIs) are approved for magnetic resonance imaging (MRIs) adverse events still occur with unacceptable frequency. Methods: In this retrospective study, magnet displacement due to MRIs was analysed. Relevant factors e.g. symptoms during MRI, diagnostics, surgical intervention following the diagnosis and possible subsequent damage were assessed.

RESULTS

16 patients were enclosed. All patients complained about pain while the scan was conducted. Computed tomography (CT) scans of the temporal bone or X-rays of the skull were performed to confirm diagnosis. Artefacts on CT scans delayed immediate diagnosis in some cases.

DISCUSSION

Despite various studies demonstrating the range of adverse events related to CIs following MRI, little information is available on diagnosis and radiologic recognition of magnet dislocation. In patients complaining about pain following an MRI scan an X-ray of the head should be performed immediately. Most adverse events occur in radiological centres without expertise in cochlear implants.

CONCLUSION

Comprehensive training of patients, surgeons and radiologists is the most efficient tool to prevent damage to the CI and the patient. X-ray of the skull is suggested to be used as the method of choice in imaging.

Management of transmodiolar and transmacular cochleovestibular schwannomas with and without cochlear implantation

Introduction

Hearing rehabilitation with cochlear implants has attracted increasing interest also for patients with cochleovestibular schwannoma. The authors report their experience with the surgical management of tumors with rare transmodiolar or transmacular extension and outcomes after cochlear implantation (CI).

Methods

This retrospective case series included nine patients with either primary intralabyrinthine tumors or secondary invasion of the inner ear from the internal auditory canal. The primary endpoint with CI, performed in six patients, was word recognition score at 65 dB SPL (sound pressure level). Secondary endpoints were intra- and postoperative electrophysiological parameters, impedance measures, the presence of a wave V in the electrically evoked (via the CI) auditory brainstem responses, the specifics of postoperative CI programming, and adverse events.

Results

Hearing rehabilitation with CI in cases of transmodiolar tumor growth could be achieved only with incomplete tumor removal, whereas tumors with transmacular growth could be completely removed. All six patients with CI had good word recognition scores for numbers in quiet conditions (80–100% at 65 dB SPL, not later than 6 to 12 months post CI activation). Four of these six patients achieved good to very good results for monosyllabic words within 1–36 months (65–85% at 65 dB SPL). The two other patients, however, had low scores for monosyllables at 6 months (25 and 15% at 65 dB SPL, respectively) with worsening of results thereafter.

Conclusions

Cochleovestibular schwannomas with transmodiolar and transmacular extension represent a rare entity with specific management requirements. Hearing rehabilitation with CI is a principal option in these patients.

Video online

The online version of this article (10.1007/s00106-020-00919-9) includes a video (2D and 3D versions) of the described surgical technique. Article and supplementary material are available at www.springermedizin.de. Please enter the title of the article in the search field, the supplementary material can be found under “Ergänzende Inhalte”.

Hearing rehabilitation after subtotal cochleoectomy using a new, perimodiolar malleable cochlear implant electrode array: a preliminary report

PURPOSE

We here report about the first surgical experience and audiological outcome using a new, perimodiolar malleable cochlear implant electrode array for hearing rehabilitation after subtotal cochleoectomy for intralabyrinthine schwannoma (ILS).

METHOD

Based on a cochlear implant with MRI compatibility of the magnet in the receiver coil up to 3 T, a cochlear implant electrode array was developed that is malleable and can be placed perimodiolar after tumor removal from the cochlea via subtotal cochleoectomy. Malleability was reached by incorporating a nitinol wire into the silicone of the electrode array lateral to the electrode contacts. The custom-made device was implanted in four patients with intracochlear, intravestibulocochlear or transmodiolar schwannomas. Outcome was assessed by evaluating the feasibility of the surgical procedure and by measuring sound field thresholds and word recognition scores.

RESULTS

After complete or partial tumor removal via subtotal cochleoectomy with or without labyrinthectomy, the new, perimodiolar malleable electrode array could successfully be implanted in all four patients. Six months after surgery, the averaged sound field thresholds to pulsed narrowband noise in the four patients were 36, 28, 41, and 35 dB HL, and the word recognitions scores for monosyllables at 65 dB SPL were 65, 80, 70, and 25% (one patient non-German speaking).

CONCLUSION

The surgical evaluation demonstrated the feasibility of cochlear implantation with the new, perimodiolar malleable electrode array after subtotal cochleoectomy. The audiological results were comparable to those achieved with another commercially available type of perimodiolar electrode array from a different manufacturer applied in patients with ILS.

Comparison of bandaging techniques to prevent cochlear implant magnet displacement following MRI

INTRODUCTION

For cochlear implants (CI) with removable magnets, a pressure bandage usually is recommended during MR imaging to avoid magnet dislocation. Nevertheless, this complication is regularly observed despite applying a pressure bandage. The aim of this study was to compare various bandaging techniques to avoid magnet displacement.

MATERIALS AND METHODS

As an experimental model a force measuring stand was developed and validated, on which the process of magnet dislocation could be simulated on a cochlear implant. In a test series with six combinations of cohesive and elastic bandages with different counter pressure elements (CPE), the forces required to induce magnet dislocation against the resistance of a compression bandage was determined. In addition, the inter- and intraindividual variability of the compression bandages was measured for ten different users.

RESULTS

The cohesive bandage had the lowest average holding force of 10.70 N. The elastic bandage developed more than four times the retention force of the cohesive bandage (44.88 N, p < 0.01). By adding a CPE, these values could be increased highly significantly up to factor 3. The optimum combination in terms of fixation force against magnet dislocation was an elastic bandage plus a cylindrical CPE (76.60 N). The data showed a high interindividual variability.

CONCLUSION

Even though most CI manufacturers now offer 3T-conditional implants, a pressure bandage will have to be applied to thousands of patients with previous implant generations to prevent magnet dislocation. We examined for the first time force measurements to compare different bandaging techniques by detecting the holding force of the CI magnet. We were able to identify an optimized combination of a bandage and a CPE to immobilize the CI magnet. However, our data also demonstrated a significant scatter amongst different examiners. Although our data provide valuable data for potential clinical application, future development of the dressing technique is required for human use.

Adverse events in pediatric cochlear implant patients undergoing magnetic resonance imaging

OBJECTIVE

To investigate the prevalence and nature of adverse events in magnetic resonance imaging (MRI) of pediatric cochlear implant (CI) patients.

METHODS

Retrospective chart review at a tertiary pediatric hospital. CI patients who underwent MRI from 2004 through 2019 were identified via our internal radiology database. Comorbidities, CI model, age at MRI, number of MRIs, type of MRIs, indication for MRIs, precautions taken for MRIs, quality of MRIs, anesthesia during MRIs, patient language abilities, and adverse events were recorded from the electronic medical record. The literature was reviewed, and our results were compared to those of previous similar series.

RESULTS

From 2004 to 2019, 12 pediatric patients (17 ears) with CIs underwent 22 MRIs. 12 MRIs were performed in CI patients with retained internal magnet. 4/22 MRIs resulted in morbidity; 2 patients experienced pain requiring MRI abortion, 1 experienced magnet rotation requiring surgical replacement, and 1 underwent operative removal of the magnet prior to the scan with surgical replacement thereafter. 19/22 MRIs were performed to evaluate the brain; 17/22 of the radiologic reports noted limitation of evaluation due to artifact. 18/22 MRIs required the administration of anesthesia. 9 of the 22 MRI events involved 2 patients whose CIs had been without internal magnet in anticipation of future MRI requirement.

CONCLUSIONS

Adverse events affecting pediatric patients with CI can occur as a result of MRI, despite appropriate precautions. Safety requires consideration of factors unique to a pediatric hearing-impaired population. Clinicians must remain informed on best practices and manufacturer recommendations.

[Management of transmodiolar and transmacular cochleovestibular schwannomas with and without cochlear implantation. German version]

INTRODUCTION

Hearing rehabilitation with cochlear implants has attracted increasing interest also for patients with cochleovestibular schwannoma. The authors report their experience with the surgical management of tumors with rare transmodiolar or transmacular extension and outcomes after cochlear implantation (CI).

METHODS

This retrospective case series included nine patients with either primary intralabyrinthine tumors or secondary invasion of the inner ear from the internal auditory canal. The primary endpoint with CI, performed in six patients, was word recognition score at 65 dB SPL (sound pressure level). Secondary endpoints were intra- and postoperative electrophysiological parameters, impedance measures, the presence of a wave V in the electrically evoked (via the CI) auditory brainstem responses, the specifics of postoperative CI programming, and adverse events.

RESULTS

Hearing rehabilitation with CI in cases of transmodiolar tumor growth could be achieved only with incomplete tumor removal, whereas tumors with transmacular growth could be completely removed. All six patients with CI had good word recognition scores for numbers in quiet conditions (80-100% at 65 dB SPL, not later than 6 to 12 months post CI activation). Four of these six patients achieved good to very good results for monosyllabic words within 1-36 months (65-85% at 65 dB SPL). The two other patients, however, had low scores for monosyllables at 6 months (25 and 15% at 65 dB SPL, respectively) with worsening of results thereafter.

CONCLUSIONS

Cochleovestibular schwannomas with transmodiolar and transmacular extension represent a rare entity with specific management requirements. Hearing rehabilitation with CI is a principal option in these patients.

MRI Observation After Intralabyrinthine and Vestibular Schwannoma Resection and Cochlear Implantation

Objective: MRI observation is part of the regular follow-up after vestibular schwannoma (VS) or intralabyrinthine schwannoma (ILS) resection. Because cochlear implantation (CI) after resection is part of the audiological rehabilitation process, the magnet resonance imaging (MRI) behavior of CI systems needs to be considered. In light of recent developments in MRI artifact positioning and pain prevention, this study evaluates reproducible MRI observations after tumor resection and CI surgery as part of follow-up. Methods: In a retrospective study, we evaluated 9 patients with a T1 KM, T2 sequence MRI observation, and cone beam computed tomography (CBCT) after ILS/VS resection and CI. In all but one case, a CI with a diametrically bipolar magnet and a receiver positioned 8-9 cm behind the external auditory canal was performed. Results: In all but one case, MRI observation allowed for a pain-free visual assessment of the intralabyrinthine and internal auditory canal (IAC) regions. In one case, a painful dislodgement of the receiver magnet occurred. Conclusion: MRI follow-up after ILS and VS resection and CI is reproducibly possible. Implant choice and positioning should be considered before implantation to allow for a pain-free visual assessment afterward. This finding allows for the first time a widening of the indication into this patient group.

Impact of Cochlear Implant With Diametric Magnet on Imaging Access, Safety, and Clinical Care

Objectives/Hypothesis

Review safety and effectiveness of magnetic resonance imaging (MRI) of patients implanted with a cochlear implant (CI) containing a diametric magnet housed within the undersurface of the device.

Study Design

Retrospective chart review with additional review of MRI at a tertiary‐care children's hospital.

Methods

Seven patients with mean age of 8.4 years (range = 1.3–19 years) with a diametric magnet in situ during MRI. The intervention comprised one or more sessions of 1.5 T or 3.0 T MRI without a head wrap. The main outcome measures were the occurrence of magnet‐related complications including discomfort and magnet displacement, use of anesthesia or sedation, and clinical usefulness of MRI studies.

Results

Seven CI recipients underwent 17 episodes of 1.5 or 3.0 T MRI with an in situ diametric magnet. Thirteen of 17 (76%) MRI sessions were completed in awake patients. No patients had device‐related discomfort. No magnet‐related complications occurred. Thirteen of 14 (93%) brain studies were clinically useful despite artifacts.

Conclusions

The diametric magnet enabled MRI with magnet in situ without the discomfort or magnet displacement associated with removable axial magnets. The reduction in MRI magnet‐related complications occurred because torque is not directed perpendicular and outward from the plane of the magnet, and the magnet is securely contained within its housing. The design of this device increased access and reduced the need for sedation or anesthesia.

Level of Evidence

4 Laryngoscope, 131:E952–E956, 2021

Assessment of a Novel 3T MRI Compatible Cochlear Implant Magnet: Torque, Forces, Demagnetization, and Imaging

HYPOTHESIS

A novel cochlea implant (CI) device magnet providing alignment to the static field of a magnetic resonance imaging (MRI) will lead to reduced torque, longitudinal forces, and demagnetization effects. The image void and distortion will be comparable to those obtained with standard CI magnets.

BACKGROUND

MRI investigations of CI users pose several challenges such as magnet dislocation, demagnetization, and may cause pain. The presence of a CI magnet within MRI field causes image distortions and may diminish the diagnostic value of an MRI procedure. Objective of this work is to evaluate magnetic forces and imaging properties of the novel CI magnet within 1.5 and 3T MRI.

METHODS

Forces and torque of the novel CI magnet were measured in both 1.5 and 3T MRI and compared with the standard magnet in 1.5T. One cadaver head was implanted with the CI devices containing the novel and standard magnets in different configurations reflecting clinical scenarios and imaging properties were assessed and compared.

RESULTS

In particular the torque has been reduced with the novel CI magnet in comparison to the standard one. Both CI magnets have not shown any signs of demagnetization. The image void and distortion was comparable between the two magnets for the main MRI clinical scanning protocols in 1.5T MRI.

CONCLUSIONS

The novel CI magnet is safe to use for MRI investigations of CI users in 3T MRI without a need for bandaging and has acceptable level of image artefacts.

First MRI With New Cochlear Implant With Rotatable Internal Magnet System and Proposal for Standardization of Reporting Magnet-Related Artifact Size

OBJECTIVE

To report on the first known magnetic resonance imaging (MRI) with a new cochlear implant (CI) with rotatable internal magnet system, to review the literature on MRI in cochlear implantees, and to advocate for standardization of reporting magnet-related artifact size.

STUDY DESIGN

Case report and review of literature.

SETTING

Tertiary care hospital.

RESULTS

A patient with congenital rubella and bilateral profound hearing loss was incidentally found to have a petroclival meningioma. After resection and radiosurgery, she underwent cochlear implantation with the Advanced Bionics HiRes Ultra 3D device (Advanced Bionics LLC, Valencia, CA) with rotatable internal magnet system, due to need for imaging surveillance of residual meningioma. During 1.5 T MRI brain scan without a head wrap, she experienced no adverse events. The images obtained were adequate for visualization of residual tumor. Implant recipients with non-rotatable magnets who undergo MRI, with or without recommended head wrap, may suffer various complications. All images in patients with retained internal magnets are subject to magnet-related artifact, but reports regarding its size are variable and lack detail on how measurements are made.

CONCLUSIONS

MRI in patients with a new CI device with rotatable magnet system may be performed without discomfort or device dislodgement at 1.5 T, even without a head wrap, though external magnet replacement may require multiple attempts due to internal magnet realignment. Despite significant artifact, the structure of interest may still be visualized for accurate diagnosis. Measuring magnet-related artifact size should be standardized by reporting artifact in radii at the image level of maximal signal loss.

Cochlear implant magnet dislocation after MRI: surgical management and outcome

PURPOSE

An increasing number of cochlear implant (CI) users is examined by magnetic resonance imaging which may cause the displacement of the implant magnet. This complication prevents the usage of the external processor and has to be treated surgically in most cases. The purpose of this study is to analyze the results of the surgical intervention and the consequences for the CI recipients.

METHODS

The retrospective study was conducted at a tertiary referral center. From the patient care records between October 2014 and July 2018, 9 cases were reviewed that had undergone MRI after cochlear implantation and had experienced magnet displacement.

RESULTS

Nine patients from 9 to 74 years of age were identified with MRI-induced magnet displacement. Implants of different manufacturers were affected (8 × Cochlear^®, 1 Advanced Bionics^®) but did not include the latest 3 T MR conditional product generation. The patients reported pain, swelling, redness above the implant and/or a noticeably dislocated magnet. One-third of the MRI examination were conducted in external radiological sites without any precautions such as a compression bandage. Surgical magnet repositioning was successful in all but one case with postoperative implant infection and consecutive explantation. In total, the patient was unable to use his CI for 420 days (1.2 years) after the MRI examination. The remaining eight patients averaged 29 days between MRI-related magnet dislocation and CI re-activation.

CONCLUSIONS

The present study shows that in the majority of cases a surgical magnet reposition is possible without complications, and thus the time of nonuse of the CI is usually low. Nevertheless, there is a risk that in individual cases significant medical, functional, social and economic consequences for patients may occur. The presented data demonstrate that the indication to perform MRI scans in CI users needs to be further critically considered. An attentive, critical assessment of an MRI indication by both the initiating physician (usually not an ENT specialist) and the performing radiologist is mandatory.

Comparison of Cochlear Implant Magnets and Their MRI Artifact Size

Introduction

Recent developments regarding cochlear implant magnets (e.g., a bipolar diametral magnet) and refined surgical techniques (e.g., implant positioning) have had a significant impact on the relation between cochlear implants and MRIs, making the reproducible visibility of cochlea and IAC possible. MRI scanning has changed from a contraindication to a diagnostic tool. Magnet artifact size plays a central role in the visual assessment of the cochlea and IAC.

Objective

The aim of this study is to compare the CI magnet-related maximum artifact sizes of various cochlea implant systems.

Materials and Methods

We performed an in vivo measurement of MRI artifacts at 1.5 and 3 Tesla with three cochlear implant magnet systems (AB 3D, Medel Synchrony, and Oticon ZTI). The implant, including the magnet, was positioned with a head bandage 7.0 cm and 120° from the nasion, external auditory canal. We used a TSE T2w MRI sequence on the axial and coronal plains and compared the artifacts in two volunteers for each tesla strength.

Results

Intraindividual artifact size differences between the three magnets are smaller than interindividual maximum artifact size differences. 3 T MRI scans, in comparison to 1.5 T MRI scans, show a difference between soft artifact areas.

Conclusion

We observed no major difference between maximum implant magnet artifact sizes of the three implant magnet types.

Special Considerations in Patients with Cranial Neurostimulatory Implants

Over the past 50 years, incredible progress has been made with implantable devices. Management can become complex, as unique issues arise with interaction of these devices with other devices and technologies. The cochlear implant (CI) is the most commonly implanted device in the head and neck. Because of its internal magnet, CIs can interfere with MRI, causing imaging artifacts, pain, and device complications. Other implants demonstrate similar issues with imaging and co-implantation. This article provides an overview of special considerations regarding neurostimulation devices within the head and neck. We focus on interactions between implantable devices and other technologies or devices.

A review of the safety of MRI in cochlear implant patients with retained magnets

The number of patients with cochlear implants (CIs) is increasing due to expanding indications, and improving CI services. Furthermore, as the use of imaging increases in clinical medicine, it is increasingly likely that patients with CIs will require a magnetic resonance imaging (MRI) examination during their lifetime. Therefore it is important that clinicians are aware of the safety aspects and manufacturer recommendations for CI patients with retained magnets. This article summarises guidelines from all major CI manufacturers and reviews the published literature on the safety of MRI in CI patients with magnets in situ. The most commonly reported complication of MRI in CI patients was pain. Other significant complications included magnet displacement, depolarisation, and polarity reversal. Artefacts caused by the CI remain an issue, but may be reduced by the use of specific sequences. Manufacturer recommendations should be followed to reduce the risk of complications, although complications may occur even when guidelines are followed. For this reason, the indication for imaging these patients should be reviewed, and patients should be appropriately counselled and consented.

Cochlear implants and 1.5 T MRI scans: the effect of diametrically bipolar magnets and screw fixation on pain

Background

The probability that a patient will need an MRI scan at least once in a lifetime is high. However, MRI scanning in cochlear implantees is associated with side effects. Moreover, MRI scan-related artifacts, dislodging magnets, and pain are often the most frequent complications. The aim of this study was to evaluate the occurrence of pain in patients with cochlear implant systems using 1.5T MRI scans.

Methods

In a prospective case study of 10 implantees, an MRI scan was performed and the degree of pain was evaluated by a visual analog scale. Scans were performed firstly with and depending on the degree of discomfort/pain, without a headband. Four of the cochlear implants contained a screw fixation. Six cochlear implants contained an internal diametrically bipolar magnet. MRI observations were performed with a 1.5 T scanner.

Results

MRI scans were performed on all patients without causing any degree of pain, even without the use of a headband.

Conclusion

Patients undergoing 1.5 T MRIs with devices including a diametrically bipolar magnet or a rigid implant screw fixation, experienced no pain, even without headbands.

[Techniques and progress in the imaging of the ear]

Ear and temporal bone imaging is essential for the diagnostic and preoperative management of middle ear lesions. The scanner is the exam of choice to analyze the walls and the contents of the middle ear. MRI is used to characterize the opacities of the middle ear and to evaluate possible neurological complications. Modern imaging techniques allow intraoperative guidance in otological surgery. Hearing implants are not always a contraindication to MRI but require precautions according to the type of implant.