MR Imaging and Cochlear Implants with Retained Internal Magnets: Reducing Artifacts near Highly Inhomogeneous Magnetic Fields

Incidental detection of bilateral cochlear implants on panoramic radiography: Case report associated with antecedent traumatic brain injury

Patients with chronic and severe hearing loss, refractory to nonsurgically-worn devices, may consider use of cochlear implants to regain auditory capability. Cochlear implants consist of surgically emplaced and externally worn components. There are few published examples of the radiographic presentation of these devices appearing in the special needs-based dental literature. This article features a case report and panoramic radiographic examination involving a 67-year-old patient who received bilateral cochlear implants after experiencing a traumatic brain injury and onset loss of hearing. A brief review of strategies for communicating with individuals with severe hearing impairment has also been provided.

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.

Field strength difference in extent of artifacts induced by CERTAS Plus valves in patients with idiopathic normal pressure hydrocephalus

BACKGROUND AND PURPOSE

: Post-shunt MRI is usually performed at 1.5T under the general assumption that shunt-related susceptibility artifacts would be greater at higher field strengths.

PURPOSE

The purpose is to show that imaging post-shunt idiopathic normal pressure hydrocephalus (iNPH) patients at 3T is feasible and with reduced artifacts as compared to 1.5T.

METHODS

We manually measured transverse dimensions of artifact at the levels of lateral ventricles, cerebral aqueduct, and cerebellar hemisphere. Areas/volumes of artifacts were calculated assuming an elliptic/ellipsoid shape. Relative extent of shunt-related artifact between field strengths was rated by 3 readers on a 5-point Likert scale. A Wilcoxon Signed Rank Test was used to compare artifact at 1.5T vs 3T for each sequence, with a significance level set at p < 0.05.

RESULTS

Artifact areas were calculated in 22 iNPH patients; artifacts were on average smaller at 3T vs 1.5T on MPRAGE, DWI, and GRE sequences. On T2 FLAIR and T2 FSE, artifacts at 3T were larger than 1.5T. On the qualitative analysis, artifact effects were less at 3T vs 1.5T on DWI, greater at 3T on T2 FSE, and had mixed results on GRE.

CONCLUSION

Our results indicate feasibility of post-shunt imaging with the CERTAS Plus valve at 3T based on shunt-related artifact that is less than or equal in extent to that on 1.5T on most standard clinical imaging sequences. Our findings, corroborated by the qualitative image review, suggest that dedicated clinical imaging sequences for devices may allow for reduction in artifact extent at both 1.5T and 3T.

Feasibility and limitations of head MRI in patients with cochlear implants

OBJECTIVE

Cochlear implants (CIs) were noncompatible with magnetic resonance imaging (MRI) initially; however, recently, implants have become available that are compatible with MRI without the need for magnet removal or bandage fixation. The images produced by MRI scans are sometimes deteriorated by artifacts and are not clinically useful. In this study, we discussed the size differences of such artifacts with respect to the imaging modality and sequences with their clinical validity.

METHODS

We performed a head MRI, using a head bandage and without magnet removal in five patients who underwent cochlear implantation at our department and analyzed the MRI findings.

RESULTS

Without magnet removal, diffusion-weighted images and T2 star-weighted images had larger artifacts and less useful images. T1-weighted images, T2-weighted images (T2WIs), T2-weighted fluid-attenuated inversion recovery (T2-FLAIR) images, and heavy T2WIs could evaluate the unimplanted side and middle of the head but had limited applicability on the CI side.

CONCLUSION

The characteristic features of MRI scan images vary with the method used as well as with the sequence, suggesting that the choice of MRI is largely determined on the basis of clinical feasibility and the requirement. Accordingly, we need to judge well in advance of imaging whether the images would be clinically relevant.

Cochlear Implant Outcomes between Patients with Sporadic and Neurofibromatosis Type 2-Associated Vestibular Schwannoma

OBJECTIVE

Compare cochlear implant (CI) performance between patients with ipsilateral sporadic vestibular schwannoma (VS) and NF2-related schwannomatosis (NF2). Compare CI performance according to VS management modality.

STUDY DESIGN

Historical cohort.

SETTING

Tertiary academic center.

PATIENTS

Forty-nine patients (52 ears) undergoing cochlear implantation in the setting of ipsilateral sporadic (n = 21) or NF2-associated VS (n = 28).

INTERVENTIONS

CI ipsilateral to VS.

MAIN OUTCOME MEASURES

Auditory thresholds, consonant-nucleus-consonant (CNC) word scores, and AzBio sentences in quiet scores.

RESULTS

Among all patients, median post-CI pure tone average was 28 dB HL (interquartile range [IQR], 21-38), CNC word score was 39% (IQR, 6-62), and AzBio sentences in quiet score was 60% (IQR, 11-83) at a median of 12.5 months postimplantation. Despite the NF2 cohort having larger tumors, when comparing patients with sporadic versus NF2-associated VS, there were no statistically significant differences in CNC word (49% [30-70] vs. 31% [0-52]) or AzBio sentences in quiet (66% [28-80] vs. 57% [5-83]) scores. Regardless of NF2 status, all patients managed with observation, and radiosurgery achieved open-set speech. In patients who underwent microsurgery, 6 (46%) of 13 with NF2 achieved open-set speech recognition compared with 4 (67%) of 6 with sporadic disease.

CONCLUSION

Select patients with VS achieve successful hearing rehabilitation with a CI. In this cohort, tumor management strategy significantly influenced CI performance, whereas differences in NF2 status exhibited less effect. Specifically, all patients managed with observation or radiosurgery achieved open-set speech perception, whereas approximately half of people with NF2-related VS and two-thirds of people with sporadic VS achieved this outcome after tumor microsurgery. When disease permits, observation and radiosurgery should be considered in patients who may later pursue a CI.

The usefulness of the O-MAR algorithm in MRI skull base assessment to manage cochlear implant-related artifacts

Objective

To assess artifact size and MRI visibility when applying the "Orthopedic-Metal Artifact Reduction" (O-MAR) algorithm for cochlear implant (CI) scanning.

Methods

Two volunteers were submitted to 1.5 T MRI with an Ultra 3D CI receiver stimulator placed on their head. Four angular CI orientations were adopted: 90, 120, 135 and 160 degrees. Volunteers were scanned in each condition using T1w and T2w TSE sequences, as well as O-MAR sequences, in both axial and coronal planes. Quantitative comparisons were made of signal void and penumbra extent. Additionally, qualitative evaluations of global image quality, MRI readability with respect to 12 anatomical structures and visibility through the penumbra were undertaken.

Results

After application of the O-MAR protocol, the radius of the signal void reduced from 50.76 mm to 45.43 mm and from 49.22 mm to 40.15 mm on T1w and T2w TSE axial sequences, respectively (p < 0.05). Qualitatively, sequences acquired with O-MAR produced better outcomes in terms of image quality and anatomical depiction. Despite the area of the penumbra being increased for the O-MAR protocol, visibility through penumbra was improved.

Conclusions

Application of O-MAR may provide a complementary strategy to those already in use to obtain diagnostically useful MRI examinations in the presence of a CI, especially in case of skull base diseases requiring MRI monitoring.

Endolymphatic Hydrops Magnet Resonance Imaging in Ménière's Disease Patients after Cochlea Implantation

INTRODUCTION

Cochlear implantation in patients with Ménière's disease (MD) is the treatment of choice in cases of functional deafness. Additional vertigo control is of central importance in this group of patients. Endolymphatic hydrops (ELH) is the pathophysiological correlate of MD and can be evaluated by magnet resonance imaging (MRI). Bilateral MD occurs in 10-33% and can be the reason for a postoperative persisting or newly occurring vertigo in this group. Recent developments in the field of implant magnets and experience in MRI sequences allow the diagnostic performance of MRI in cochlear implantees to be evaluated. The aim of the present study was to evaluate the possibility of MRI as a visual diagnostic tool for endolymphatic hydrops in cochlear implantees.

MATERIAL AND METHODS

This was a retrospective study including three cochlear implantees (age: 61-76 years, one female, two male) suffering from MD who, postoperatively, had a recurrence of vertigo with Ménière's-like symptoms. An MRI was performed for the evaluation of ELH (ELH-MRI). MRI observation was performed by a 4 h iv. delayed Gad 3 D Flair sequence.

RESULTS

In all cases, the ipsilateral implant magnet artifact covered the vestibulum, the semicircular canals and the cochlea. The contralateral vestibulum, the semicircular canal and the cochlea were fully observable, and a classification of the ELH-MRI could be performed.

CONCLUSION

ELH-MRI scanning allows for the detection of contralateral labyrinthine endolymphatic hydrops and is a tool for the postoperative evaluation of vertigo in cochlear implantees.

Image Quality and Artifact Reduction of a Cochlear Implant With Rotatable Magnets

OBJECTIVE

To determine if metal reduction magnetic resonance imaging sequences and changes in implant placement minimize artifact from cochlear implants and improve visualization of intracranial structures.

STUDY DESIGN

Cadaveric study.

SETTING

Tertiary referral center.

PATIENTS

Five cadaveric heads.

INTERVENTIONS

Specimens were implanted with Advanced Bionics HiRes Ultra3D devices at nasion-external auditory canal angles of 90, 120, and 160 degrees, and distances from the external auditory canal of 9 or 12 cm. Standard brain/internal auditory canal (IAC) sequences with metal artifact reducing technique were acquired in a 1.5T scanner.

MAIN OUTCOME MEASURES

The primary outcome was visibility of 14 intracranial structures graded on a 4-point scale (1, structures <50% visible; 2, >50% visible with some areas nonvisible from artifact; 3, artifact present but adequate for diagnosis; and 4, high quality). Scores were determined by experienced head and neck radiologists and compared with one-way analysis of variance.

RESULTS

Imaging sequences included axial 5-mm whole-brain turbo spin echo (TSE) T2 with right to left and anterior to posterior encoding, fluid-attenuation inversion recovery high bandwidth, axial 5-mm whole-brain slice-encoding metal artifact correction (SEMAC), axial IAC constructive interference in steady state, and axial 3-mm T1 IAC with and without fat saturation. T1 IACs in axial and coronal planes were best for ipsilateral structures overall (mean [standard deviation {SD}], 3.8 [0.6] and 3.8 [0.5]). SEMAC (mean [SD], 3.5 [0.8]) was superior to TSE with anterior to posterior encoding (mean [SD], 3.5 [0.9) for ipsilateral cortex, cerebellopontine angle, and brainstem/cerebellum, and equivalent for the inner ear. Constructive interference in steady state and T1 with fat saturation were poor for all ipsilateral structures (mean, 2.8 [ p < 0.01]; mean, 3.1 [ p < 0.01]). The 120 degrees/12 cm position was overall best, although the 120 degrees/9 cm position still afforded visualization of ipsilateral structures; other angles and distances conferred slight advantages for specific structures of interest.

CONCLUSIONS

SEMAC and T2 TSE with anterior to posterior encoding sequences provide artifact suppression while retaining excellent image quality. Different placement angles did not confer improvement in visualization, although placement distances provided slight advantages for some structures.

Disease recidivism after subtotal petrosectomy and ear canal closure

PURPOSE

To describe the presentation, diagnosis, and management of chronic otitis media recidivism after subtotal petrosectomy and ear canal closure (STP).

MATERIALS AND METHODS

Patients with temporal bone pathology detected during follow-up after STP were identified in the electronic medical record. Pertinent clinical details regarding surveillance plan, presentation, imaging findings, and revision surgery were collected and analyzed.

RESULTS

A total of 10 patients were identified with recurrent or persistent pathology after STP. The median time to detection was 46 months (IQR 24-84). Five patients (50 %) had non-specific symptomatology, 4 patients (40 %) were completely asymptomatic, and 1 patient (10 %) was asymptomatic outside of two instances of mastoiditis with cochlear implant device infection treated with incision and drainage. One patient (10 %) was noted to have proptosis on examination, but no other patients had objective signs of disease at detection of disease recidivism. Nine (90 %) patients had pathology identified on preoperative imaging. All patients underwent revision surgery, with identification of cholesteatoma in 8 cases (80 %) and cholesterol granuloma in 2 cases (20 %). Extensive disease was noted in 6 patients (60 %), all of whom followed-up greater than 3 years from surgery. All patients tolerated revision surgery without complication.

CONCLUSIONS

Recidivistic disease often remains clinically silent for extended periods of time after STP. Planned follow-up - with imaging or second look surgery - to facilitate early detection should be considered. Undetected disease recurrence or development may result in morbidity in a proportion of patients if surveillance is not performed.

Effect of Head Position and Magnetic Resonance Sequence on Cochlear Implant-Related Artifact Size and Internal Auditory Canal Visibility

HYPOTHESIS

To assess whether cochlear implant (CI)-related magnetic resonance imaging (MRI) artifact and visibility of the internal auditory canal (IAC) can be improved with head positioning and select MRI sequences.

BACKGROUND

CI-related MRI artifact limits the use of CIs in otherwise good candidates because of the need for serial MRIs for monitoring of pathology. This most notably impacts patients with tumors of the cerebellopontine angle and IAC.

METHODS

Two cadaver heads were implanted with either a Med-El CONCERT (fixed magnet) or SYNCHRONY (rotating magnet) device. Each head was imaged in a 1.5T scanner in 11 different positions. The SYNCHRONY-implanted head was also imaged in a 3.0T scanner in seven positions. Artifact size and IAC visibility (graded on a Likert scale) were measured for each head position by a neuroradiologist.

RESULTS

The CONCERT CI produced significantly smaller artifact than the SYNCHRONY CI (effect size, 14.65 mm; p < 0.001). There was no significant difference between CI models in regard to IAC visibility. No head positions were statistically significantly better than neutral position for minimizing artifact size or IAC visibility, although some positions resulted in significantly larger artifact (effect sizes, 2.1-14.3 mm; p < 0.05) or significantly poorer IAC visibility (effect size, 1.4; p < 0.01). The T2 three-dimensional (CISS/FIESTA) sequence demonstrated significantly smaller artifact than T1 sequences, whereas T1 sequences demonstrated significantly better IAC visibility than T2 sequences.

CONCLUSION

Head positioning and magnetic resonance sequence selection impact CI-related artifact size and IAC visibility.

Safety Considerations in MRI and CT

OBJECTIVE

MRI and CT are indispensable imaging modalities for the evaluation of patients with neurologic disease, and each is particularly well suited to address specific clinical questions. Although both of these imaging modalities have excellent safety profiles in clinical use as a result of concerted and dedicated efforts, each has potential physical and procedural risks that the practitioner should be aware of, which are described in this article.

LATEST DEVELOPMENTS

Recent advancements have been made in understanding and reducing safety risks with MR and CT. The magnetic fields in MRI create risks for dangerous projectile accidents, radiofrequency burns, and deleterious interactions with implanted devices, and serious patient injuries and deaths have occurred. Ionizing radiation in CT may be associated with shorter-term deterministic effects on biological tissues at extremely high doses and longer-term stochastic effects related to mutagenesis and carcinogenesis at low doses. The cancer risk of radiation exposure in diagnostic CT is considered extremely low, and the benefit of an appropriately indicated CT examination far outweighs the potential risk. Continuing major efforts are centered on improving image quality and the diagnostic power of CT while concurrently keeping radiation doses as low as reasonably achievable.

ESSENTIAL POINTS

An understanding of these MRI and CT safety issues that are central to contemporary radiology practice is essential for the safe and effective treatment of patients with neurologic disease.

Treated large posterior fossa vestibular schwannoma and meningioma: Hearing outcome and willingness-to-accept brain implant for unilateral deafness

Background/Objective

To compare functional hearing and tinnitus outcomes in treated large (~ 3 cm) vestibular schwannoma (VS) and posterior fossa meningioma cohorts, and construct willingness-to-accept profiles for an experimental brain implant to treat unilateral hearing loss.

Methods

A two-way MANOVA model with two independent variables (tumor type; time from treatment) and three dependent variables (hearing effort of tumor ear; abbreviated Speech, Spatial, and Qualities of Hearing scale (SSQ12); Tinnitus Functional Index (TFI)) was used to analyze data from VS (N = 32) and meningioma (N = 50) patients who were treated at a tertiary care center between 2010 and 2020. A query to probe acceptance of experimental treatment for hearing loss relative to expected benefit was used to construct willingness-to-accept profiles.

Results

Tumor type was statistically significant on the combined dependent variables analysis (F[3, 76] = 19.172, p < .0005, Wilks' Λ = 0.569). Meningioma showed better outcome for hearing effort (F[1, 76] = 14.632, p < .0005) and SSQ12 (F[1, 76] = 16.164, p < .0005), but not for TFI (F[1, 76] = 1.247, p = .268) on univariate two-way ANOVA analyses. Superior hearing effort and SSQ12 indices in the short-term (< 2 years) persisted in the long-term (> 2 years) (p ≤ .017). At the 60% speech understanding level, 77% of respondents would accept an experimental brain implant.

Conclusion

Hearing outcome is better for posterior fossa meningioma compared to VS. Most patients with hearing loss in the tumor ear would consider a brain implant if the benefit level would be comparable to a cochlear implant.

Level of Evidence

2.

Clinical viability of magnetic bead implants in muscle

Human movement is accomplished through muscle contraction, yet there does not exist a portable system capable of monitoring muscle length changes in real time. To address this limitation, we previously introduced magnetomicrometry, a minimally-invasive tracking technique comprising two implanted magnetic beads in muscle and a magnetic field sensor array positioned on the body's surface adjacent the implanted beads. The implant system comprises a pair of spherical magnetic beads, each with a first coating of nickel-copper-nickel and an outer coating of Parylene C. In parallel work, we demonstrate submillimeter accuracy of magnetic bead tracking for muscle contractions in an untethered freely-roaming avian model. Here, we address the clinical viability of magnetomicrometry. Using a specialized device to insert magnetic beads into muscle in avian and lagomorph models, we collect data to assess gait metrics, bead migration, and bead biocompatibility. For these animal models, we find no gait differences post-versus pre-implantation, and bead migration towards one another within muscle does not occur for initial bead separation distances greater than 3 cm. Further, using extensive biocompatibility testing, the implants are shown to be non-irritant, non-cytotoxic, non-allergenic, and non-irritating. Our cumulative results lend support for the viability of these magnetic bead implants for implantation in human muscle. We thus anticipate their imminent use in human-machine interfaces, such as in control of prostheses and exoskeletons and in closed-loop neuroprosthetics to aid recovery from neurological disorders.

Quality-of-Life Outcomes After Modified Subtotal Petrosectomy With Ear Canal Closure for Chronic Otitis Media

OBJECTIVE

To assess quality-of-life (QoL) outcomes after modified subtotal petrosectomy with ear canal closure (mSTP) for chronic otitis media.

STUDY DESIGN

Survey study.

SETTING

Tertiary referral center.

PATIENTS

Patients with chronic otitis media.

INTERVENTIONS

mSTP.

MAIN OUTCOME MEASURES

Survey results from enrolled patients on the validated disease-specific Chronic Ear Survey (CES) and Chronic Otitis Media Outcome Test-15 (COMOT-15) regarding their current state of health and, if surgery was performed within 3 years of enrollment, their state of health before mSTP.

RESULTS

A total of 23 patients were studied, including 19 who underwent surgery within 3 years of enrollment. Postoperatively, mean total CES scores were 80 and COMOT-15 scores were 41, with a higher CES and a lower COMOT-15 indicating better QoL. There were statistically significant improvements after mSTP in the CES activity restriction (25% difference; p = 0.008), symptom (17% difference; p = 0.007), and medical resource (13% difference; p = 0.03) domain and total (18% difference; p = 0.006) scores. In addition, there were statistically significant improvements in the COMOT-15 ear symptom (-22% difference; p < 0.001) domain and total (-16% difference; p = 0.01) scores; however, improvements in the hearing function and mental health domains did not achieve statistical significance. Postoperative COMOT-15 total scores were significantly better for patients who underwent aural rehabilitation compared to those who did not (-17% difference; p < 0.001).

CONCLUSION

Modified subtotal petrosectomy with ear canal closure is a useful intervention for patients with recalcitrant chronic otitis media, offering improved QoL in appropriately selected patients. Aural rehabilitation, when feasible, provides the potential for further QoL improvement.

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.

Cochlear Implantation in Neurofibromatosis Type 2: Experience From the UK Neurofibromatosis Type 2 Service

OBJECTIVE

To review the outcomes of cochlear implants (CI) in patients with neurofibromatosis type 2 (NF2) in a large cohort, and identify factors associated with poor hearing benefit.

STUDY DESIGN

Fifteen-year retrospective national observational case series.

SETTING

United Kingdom regional NF2 multidisciplinary teams.

PATIENTS

Consecutive patients with NF2 receiving a CI.

INTERVENTIONS

CI for hearing rehabilitation.

MAIN OUTCOME MEASURES

1) Audiometric performance at 9 to 12 months after implantation using City University of New York (CUNY) sentence recognition score, and Bamford- Kowal-Bench (BKB) word recognition score in quiet (BKBq), and in noise (BKBn). 2) CI use at most recent review.

RESULTS

Sixty four consecutive patients, median age 43 years, were included. Nine to 12 months mean audiometric scores were: CUNY 60.9%, BKBq 45.8%, BKBn 41.6%. There was no difference in audiometric outcomes between VS treatment modalities. At most recent review (median 3.6 years from implantation), 84.9% with device in situ/available data were full or part-time users. Between 9 and 12 months and most recent review there was an interval reduction in mean audiometric scores: CUNY -12.9%, BKBq -3.3%, BKBn -4.9%. Larger tumor size and shorter duration of profound hearing loss were the only variables associated with poorer audiometric scores. Tumor growth at the time of surgery was the only variable associated with CI non-use. Individual patient response was highly variable.

CONCLUSIONS

CI can provide significant and sustained auditory benefits to patients with NF2 independent of tumor treatment modality, with the majority of those implanted becoming at least part-time users. Larger datasets are required to reliably assess the role of independent variables.

Dimensions and forms of artefacts in 1.5 T and 3 T MRI caused by cochlear implants

Cochlear implantation is a standard treatment option due to expanding indications. Cranial magnetic resonance imaging (cMRI) has become a widespread diagnostic tool. Therefore, an increased number of cochlear implant (CI) users are undergoing cMRI scans. This study aimed to investigate the issue of the CI magnet impacting MRI quality and artifacts. 1.5 T and 3 T MRI scans with 4 defined sequences (T2-TSE, T2-TIRM, T1-3D-MPRAGE, and TDI) were performed on a phantom with a CI (SYNCHRONY System by MED-EL Austria) in place. The resulting MRI artifacts were retrospectively compared to MRI artifacts observed in patients with a CI. All images were transferred to AMIRA and visualized by manual segmentation. Usable image quality was achieved in three sequences (T2-TSE, T2-TIRM and T1-mprage). Observed artifacts differed in shape and size depending on the sequence. Maximum diameters of signal void areas ranged from 58 × 108 × 98 mm to 127 × 123 × 153 mm. Image distortions were larger. MRI artifacts caused by the SYNCHRONY system are asymmetric with varying shape, depending on the sequence. The phantom artefacts are similar to those in CI users. Considering the observed asymmetry, the hypothesis of varying implantation locations resulting in varying positions of the signal void area needs to be further investigated.

Parametric Assessment of the Effect of Cochlear Implant Positioning on Brain MRI Artefacts at 3 T

BACKGROUND

Brain magnetic resonance imaging in patients with cochlear implants (CIs) is impacted by image artefacts.

HYPOTHESIS

The optimal positioning of the CI to minimize artefacts is unknown. This study aimed to characterize the dependence of the extent and distribution of the artefact on CI positioning.

METHODS

Three normally hearing individuals underwent magnetic resonance imaging using a standard T1-weighted 3D sequence. Scans were acquired with a non-functioning CI placed underneath a swimming cap at four plausible scalp positions on each side, and without the CI in situ. The artefact in each image was assessed quantitatively using voxel-based techniques. Two radiologists also independently rated the likely impact of the artefact on the detection of pathology for 20 neuroradiological locations.

RESULTS

The procedure was well tolerated. The most postero-inferior CI positions resulted in the smallest apparent artefacts. Radiological evaluations suggested that artefacts would likely limit pathology detection in the ipsilateral temporal, parietal, and occipital lobes, regardless of CI location. Pathology detection in contralateral structures and anterior corpus callosum was rarely affected. Certain CI locations appeared to selectively spare ipsilateral structures, for example, postero-inferior CI locations selectively spared ipsilateral midbrain, deep grey matter, and frontal lobes.

CONCLUSION

A CI placed under a swimming cap is a feasible tool for observing the effect of CI location on image usability within a single subject and potentially informing surgical planning. Regardless of CI placement, artefacts involving ipsilateral parietal, temporal, and occipital lobes severely limited diagnostic image utility. Between 35% and 70% of neuroradiological features were deemed unaffected by the implant.

Cochlear Implantation in Vestibular Schwannoma: A Systematic Literature Review

Objective  Ipsilateral cochlear implantation (CI) in vestibular schwannoma (VS) has been an emerging trend over the last two decades. We conducted the first systematic review of hearing outcomes comparing neurofibromatosis 2 (NF2) and sporadic VS undergoing CI. A comparison of the two populations and predictor of outcome was assessed. This is an update to a previously presented study. Data Sources  Systemic data searches were performed in PubMed NCBI and Scopus by an academic librarian. No restrictions based on the year of publication were used. Study Selection  Studies were selected if patients had a diagnosis of NF2 and a CI placed in the affected side with reports of hearing outcome. Two independent reviewers screened each abstract and full-text article. Data Extraction  Studies were extracted at the patient level, and the assessment of quality and bias was evaluated according to the National Institutes of Health Quality Assessment Tool. Main Outcome Measures  Outcome predictors were determined by using the chi-square test and Student's t -test. Results  Overall, most CI recipients functioned in the high-to-intermediate performer category for both sporadic and NF2-related VS. Median AzBio (Arizona Biomedical Institute Sentence Test) was 72% (interquartile range [IQR]: 50) in NF2 patients and 70% (IQR: 7.25) in sporadic patients. Larger tumor size predicted a poorer final audiometric outcome. Conclusions  Categorization of hearing outcome into superior performance and inferior performance based on sentence recognition revealed a generally good hearing outcome regardless of treatment or patient population. Select patients with sporadic and NF2 VS may benefit from CI.

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.

Quality Control after Intracochlear Intralabyrinthine Schwannoma Resection and Cochlear Implantation

Background: The combination of intralabyrinthine schwannoma (ILS) removal and cochlear implantation is the standard of care after surgical resection for audiological rehabilitation. Intracochlear ILS is not only the most frequent tumor in this group of schwannomas, but it is also, to some degree, surgically the most challenging because of its position behind the modiolus. Recent developments in the knowledge of implant position, implant magnet choice, and magnetic resonance imaging (MRI) sequences make an MRI follow-up after surgical removal possible. Thus far, no results are known about the surgical success and residual rate of these kind of tumors. The aim of the present study was to perform an early MRI follow-up for the evaluation of residual or recurrent intracochlear ILS after surgical removal and cochlear implantation. Methods: In a retrospective study, we evaluated seven patients after an intracochlear ILS removal and single-stage cochlear implantation with a mean period of 13.4 months post surgery with a 3T T1 GAD 2 mm sequence for a residual ILS. Patients were operated on using an individualized technique concept. Results: In six out of seven cases, 3 T T1 GAD 2 mm MRI follow-up showed no residual or recurrent tumor. In one case, a T1 signal indicated a tumor of the upper inner auditory canal (IAC) at the MRI follow up. Conclusion: MRI follow-up as a quality control tool after ILS removal and cochlear implantation is highly important to exclude residual tumors. Long-term MRI evaluation results are needed and can be obtained under consideration of implant position, implant magnet, and MRI sequence choice. A preoperative MRI slice thickness less than 2 mm can be recommended to visualize possible modiolar and IAC expansion.

The role of cochlear implant positioning on MR imaging quality: a preclinical in vivo study with a novel implant magnet system

Purposes

To investigate the effects for Ultra 3D cochlear implant (CI) positioning on MR imaging quality, looking at a comprehensive description of intracranial structures in cases of unilateral and bilateral CI placement.

Methods

Four CI angular positions (90°, 120°, 135° and 160°) at 9 cm distance from the outer-ear canal were explored. The 1.5 T MRI assessment included our institutional protocol for the investigation of brain pathologies without gadolinium application. Three investigators (two experienced neuroradiologists and one experienced otoneurosurgeon) independently evaluated the MR findings. A 4-point scale was adopted to describe 14 intracranial structures and to determine which CI positioning allowed the best image quality score and how bilateral CI placement modified MRI scan visibility.

Results

A high positive correlation was found between the three blinded observers. Structures situated contralateral from the CI showed high-quality values in all four placements. Structures situated ipsilaterally provided results suitable for diagnostic purposes for at least one position. At 90°, artifacts mainly involved brain structures located cranially and anteriorly (e.g., temporal lobe); on the contrary, at 160°, artifacts mostly influenced the posterior fossa structures (e.g., occipital lobe). For the bilateral CI condition, MR imaging examination revealed additional artifacts involving all structures located close to either CI, where there was a signal void/distortion area.

Conclusions

Suitable unilateral CI positioning can allow the visualization of intracranial structures with sufficient visibility for diagnostic purposes. Bilateral CI positioning significantly deteriorates the anatomical visibility. CI positioning might play a crucial role for patients who need post-operative MRI surveillance.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00405-021-07005-y.

Intraoperative Cochlear Nerve Monitoring for Vestibular Schwannoma Resection and Simultaneous Cochlear Implantation in Neurofibromatosis Type 2: A Case Series

BACKGROUND

Neurofibromatosis type 2 (NF2) often results in profound hearing loss and cochlear implantation is an emerging hearing rehabilitation option. However, cochlear implant (CI) outcomes in this population vary, and intraoperative monitoring to predict cochlear nerve viability and subsequent outcomes is not well-established.

OBJECTIVE

To review the use of intraoperative electrically evoked cochlear nerve monitoring in patients with NF2 simultaneous translabyrinthine (TL) vestibular schwannoma (VS) resection and cochlear implantation.

METHODS

A retrospective review was performed of 3 patients with NF2 that underwent simultaneous TL VS resection and cochlear implantation with electrical auditory brainstem response (eABR) measured throughout tumor resection. Patient demographics, preoperative assessments, surgical procedures, and outcomes were reviewed.

RESULTS

Patients 1 and 3 had a reliable eABR throughout tumor removal. Patient 2 had eABR pretumor removal, but post-tumor removal eABR presence could not be reliably determined because of electrical artifact interference. All patients achieved auditory percepts upon CI activation. Patients 1 and 2 experienced a decline in CI performance after 1 yr and after 3 mo, respectively. Patient 3 continues to perform well at 9 mo. Patients 2 and 3 are daily users of their CI.

CONCLUSION

Cochlear implantation is attainable in cases of NF2-associated VS resection. Intraoperative eABR may facilitate cochlear nerve preservation during tumor removal, though more data and long-term outcomes are needed to refine eABR methodology and predictive value for this population.

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.

Safety of active auditory implants in magnetic resonance imaging

Magnetic resonance imaging (MRI) has become the gold standard for the diagnosis of many pathologies. Using MRI in patients with auditory implants can however raise concerns due to mutual interactions between the implant and imaging device, resulting in potential patient risks. Several implant manufacturers have been working towards more MRI safe devices. Older devices are however often labelled for more stringent conditions, possibly creating confusion with patients and professionals. With this myriad of different devices that are implanted in patients for lifetimes of at least 20 years, it is crucial that both patients and professionals have a clear understanding of the safety of their devices. This work aims at providing an exhaustive overview on the MRI safety of active auditory implants. The available industry standards that are followed by manufacturers are outlined and an overview of the latest scientific developments focusing on the last five years is provided. In addition, based on the analysis of the adverse events reported to the Food and Drug Administration (FDA) and in literature within the past ten years, a systematic review of the most commonly occurring issues for patients with auditory implants in the MRI environment is provided. Results indicate that despite the release of more MRI conditional active hearing implants on the market, adverse events still occur. An extensive overview is provided on the MRI safety of active auditory implants, aiming to increase the understanding of the topic for healthcare professionals and contribute to safer scanning conditions for patients.

Magnetic resonance imaging in children with implants

As access to MRI in pediatrics increases, the radiologist needs to become acquainted with the basic principles of MRI safety. As part of the image acquisition, the static magnetic field, gradient system, and the radiofrequency transmit-receive coil interact with medical and non-medical implants and can result in serious injury. The main stage of risk triage is based on the determination of whether the implant is MRI-safe, conditional, unsafe or unknown. Guiding principles include the strict adherence to manufacturer specifications for MRI-conditional implants and the assumption that an unknown implant is MR-unsafe. In this article we review considerations for common medical implants encountered in pediatrics including ventriculoperitoneal shunts, orthopedic hardware, orthodontic hardware, pacemakers, vascular stents, vagal nerve stimulators and cochlear implants. Finally, we review a set of high-yield considerations, including the non-communicative patient (sedated or non-verbal), susceptibility artifacts from unclear source, and the approach to an unknown implant.

Utilization of SEMAC-VAT MRI for Improved Visualization of Posterior Fossa Structures in Patients With Cochlear Implants

OBJECTIVE

The number of cochlear implant (CI) users is ever increasing worldwide, as is the utilization of magnetic resonance imaging (MRI) as a key diagnostic modality for pathology of the brain and surrounding structures. Despite advances in MRI compatibility with CI, metal artefact remains a significant issue that needs to be addressed. We test our hypothesis that the slice encoding for metal artefact correction and view angle tilting (SEMAC-VAT) metal artefact reduction technique improves demonstration of posterior fossa structures on MRI in CI recipients.

STUDY DESIGN

A retrospective case review.

SETTING

A tertiary referral hearing implant and skull base center.

INTERVENTIONS

Dedicated MRI of the posterior fossa using T1 spin echo post-gadolinium sequences with and without the application of SEMAC-VAT in CI recipients.

MAIN OUTCOME MEASURES

Extent and severity of the artefact and visualization of surrounding anatomic structures with and without the application of SEMAC-VAT, allowing for direct comparison.

RESULTS

Eight CI recipients with nine CI devices were analyzed. We noted a significant reduction in signal void and improved visibility of the ipsilateral hemisphere in every case. Penumbra size increased although there was improved visibility through the penumbra. There was improved visualization of key intracranial structures, such as the ipsilateral internal auditory canal, cerebellopontine angle, cerebellar hemisphere, and brainstem.

CONCLUSIONS

Application of SEMAC-VAT produces a significant reduction in signal void and improved visualization of key structures within the temporal bone and posterior cranial fossa in patients with CIs without the need for removal of the internal magnet.

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.

MRI-induced artifact by a cochlear implant with a novel magnet system: an experimental cadaver study

Purposes

To primarily evaluate MRI-induced effects for Ultra 3D cochlear implantation in human cadavers in terms of artifact generation and MR image quality.

Methods

Three human cadaveric heads were submitted to imaging after unilateral and bilateral cochlear implantation. The 1.5 T MR examination protocol was chosen in accordance with our institutional protocol for the assessment of brain pathology. The maximal signal void size was measured according to each sequence and plane. Two experienced neuro-radiologists and one experienced otoneurosurgeon independently evaluated the MR image quality findings. A 4-point scale was used to describe the diagnostic usefulness of 14 brain structures.

Results

Shape and size of the artifacts were found to be highly related to MRI sequences and acquisition planes. MRI sequences and processing algorithms affected the ability to assess anatomical visibility. Image quality appeared either high or assessable for diagnostic purposes in 9 out of 14 of the ipsilateral structures, in at least one plane. Anatomical structures contralateral to the cochlear implant were highly visible in all conditions. Artifact intrusion clearly improved after application of metal artifact-reduction techniques. In the case of bilateral cochlear implant, a mutual interaction between the two implant magnets produced an additional artifact.

Conclusions

We performed the first cadaver study aimed at systematically evaluating the MRI-induced artifacts produced by a cochlear implant with a novel four bar magnet system. Specific brain structures can be assessable for diagnostic purposes under 1.5 T MRI, with the cochlear implant magnet in place.

MR Safety: Active Implanted Electronic Devices

New implanted medical devices continue to be made available for treatment of medical conditions. Many recipients can benefit from the diagnostic power of MR imaging. Provisions must be made to determine if these patients can be safely scanned. Metal-containing devices can be considered either MR unsafe or conditional. It is essential that all components of an implanted system are completely and accurately identified, with the most restrictive MR safety condition dictating the scanning approach. MR safety considerations for major classes of implanted devices are discussed, recognizing that there have been reports of serious device-related MR safety incidents.

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.

MRI surveillance following concurrent cochlear implantation in cases of vestibular schwannoma resection

OBJECTIVE

Cochlear nerve preserving translabyrinthine vestibular schwannoma (VS) resection enables concurrent cochlear implantation. Implantation in patients with VS raises important concerns including the ability to undergo postoperative magnetic resonance imaging (MRI) monitoring of residual tumor growth or tumor recurrence, specifically with a retained magnet. We aim to assess the feasibility of MRI monitoring and the impact on image quality with retained cochlear implant (CI) magnets.

METHODS

Retrospective review of post-operative head MRI scans in CI recipients with a retained CI magnet, after cochlear nerve preserving translabyrinthine excision of VS. The ability to visualize the ipsilateral and contralateral internal auditory canal (IAC) and cerebellopontine angle (CPA) were assessed.

RESULTS

A total of eight surveillance head MRI were performed in six patients. In one case, in which the receiver was positioned lower, the view of the ipsilateral IAC and CPA was distorted. In all other cases, the views of both the ipsilateral and contralateral IAC and CPA were overall unimpaired.

DISCUSSION

Imaging artifact only very rarely impedes adequate visualization of the ipsilateral IAC or CPA in CI recipients. In anticipation of the need for further IAC and CPA imaging, it would be advisable to place the receiver in an exaggerated superior-posterior position to further decrease obscuring artifact. Thus, serial monitoring of VS tumors can be performed safely with preservation of image quality with a retained receiver magnet.

CONCLUSIONS

When placing the CI receiver-stimulator farther posterior-superiorly, excellent visualization of the IAC and CPA can be accomplished without significantly impairing the image quality.

Hearing rehabilitation outcomes in cochlear implant recipients with vestibular schwannoma in observation or radiotherapy groups: A systematic review

Objectives: Vestibular schwannomas (VS) are rare benign tumours of the vestibular nerve that cause hearing loss. Management strategies include watchful waiting, radiotherapy or surgical resection. Historically, the presence of retrocochlear disease has been considered to be a contra-indication to cochlear implantation (CI). The aim of this systematic review is to assess hearing rehabilitation outcomes for CI recipients with VS, either sporadic or associated with neurofibromatosis type 2, whose tumours have been managed with either observation or radiotherapy.Methods: PubMed, Embase, and Cochrane Library databases were searched from inception through to November 2018. 50 cases from 12 studies met the inclusion criteria. Patient demographics, VS characteristics, management strategy, pre-CI hearing status, electrical promontory stimulation testing, post-CI hearing status and speech perception scores, functional benefits and follow-up length are reported.Results: Radiotherapy and observation groups had similar patient demographics in terms of age at CI, tumour size and duration of deafness. Following CI, 64% and 60% of patients in the radiotherapy and observation groups achieved open-set speech perception, respectively. Pure tone average thresholds (33 vs. 39 dB) and speech scores were also comparable between both groups.Conclusion: Ipsilateral CI in patients with VS that have not been surgically resected can provide beneficial hearing rehabilitation outcomes.

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 Implantation in Sporadic Vestibular Schwannoma: A Systematic Literature Review

Objective  This study was aimed to perform a systematic literature review by examining outcomes in patients with sporadic vestibular schwannoma (VS) undergoing ipsilateral cochlear implant (CI). Data Sources  PubMed-NCBI (National Center for Biotechnology Information) and Scopus databases were searched through October 2017. Study Selection  Studies reporting auditory outcomes for each patient when a CI was placed with an ipsilateral sporadic VS were included. Main Outcome Measures  Demographic variables, VS characteristics, preoperative hearing metrics, duration of deafness, CI type, approach to tumor resection, postoperative auditory outcomes, and postoperative tinnitus outcomes were reported for each eligible patient within studies. Each study was evaluated for quality and bias. Results  Fifteen studies and 45 patients met inclusion criteria. Mean speech discrimination score (SDS) improved from 30.0 to 56.4% after CI placement. The majority when reported had an improvement in tinnitus. Preoperative ipsilateral SDS was a negative predictor of postoperative SDS, while neither tumor resection status, tumor location, duration of deafness, ipsilateral pure tone average, nor timing of CI placement had a significant effect on patient outcome. Conclusions  Notwithstanding the challenges inherent with surveillance magnetic resonance imaging (MRI) in the setting of a cochlear implant magnet, select sporadic vestibular schwannoma patients can be considered for cochlear implantation.

Cochlear Implantation: An Overview

A cochlear implant (CI) is a surgically implanted device for the treatment of severe to profound sensorineural hearing loss in children and adults. It works by transducing acoustic energy into an electrical signal, which is used to stimulate surviving spiral ganglion cells of the auditory nerve. The past 2 decades have witnessed an exponential rise in the number of CI surgeries performed. Continual developments in programming strategies, device design, and minimally traumatic surgical technique have demonstrated the safety and efficacy of CI surgery. As a result, candidacy guidelines have expanded to include both pre and postlingually deaf children as young as 1 year of age, and those with greater degrees of residual hearing. A growing proportion of patients are undergoing CI for off-label or nontraditional indications including single-sided deafness, retrocochlear hearing loss, asymmetrical sensorineural hearing loss (SNHL) in adults and children with at least 1 ear that is better than performance cut-off for age, and children less than 12 months of age. Herein, we review CI design, clinical evaluation, indications, operative technique, and outcomes. We also discuss the expanding indications for CI surgery as it relates to lateral skull base pathology, comparing CI to auditory brainstem implants, and address the concerns with obtaining magnetic resonance imaging (MRI) in CI recipients.