Dimensions of artefacts caused by cochlear and auditory brainstem implants in magnetic resonance imaging.

Background: The aim of the study was to investigate the extent of MRI artefacts due to the magnet of selected auditory implants.Study design: Artefacts of the Synchrony cochlear implant at 1.5 T as well as at 3 T MRI devices were examined in cadavers and compared to the artefacts in MRI scans at 1.5 T of 17 patients implanted with CI (n = 12) and auditory brainstem implants (ABI) (n = 5).Results: None of the scanned implants showed any failure after MRI. After removal of the magnet, only a portion of the images in the direct neighbourhood of the implant, especially in the temporal and parietal lobe, contained artefacts. More anatomical substructures were visible without artefacts using the MedEl Synchrony device.Conclusion: Artefacts can be markedly reduced by rotating, self-aligning magnet. Removal of the magnet also results in reduction of artefacts.

Neural Substrates of Tinnitus in an Auditory Brainstem Implant Patient: A Preliminary Molecular Imaging Study Using H2 15 O-PET Including a 5-year Follow-up of Auditory Performance and Tinnitus Perception.

INTRODUCTION: It was previously demonstrated that tinnitus due to profound unilateral hearing loss can be treated by the use of electrical stimulation via a cochlear implant (CI) with long-lasting positive effects. In cases where patients are not suitable for cochlear implantation due to aplasia/hypoplasia, cochlear malformations etc., an auditory brainstem implant (ABI) may be a solution. While auditory performance with ABI is well investigated, it is currently unknown whether stimulation through ABI also renders tinnitus reduction in patients with incapacitating tinnitus. The current case study reports on the subjective tinnitus perception during a 5-year follow-up period. In addition, a first H2O PET imaging study in an ABI patient is carried out revealing underlying neural substrates of tinnitus. METHODS: A 56-year-old male single-sided deaf patient with incapacitating tinnitus received an ABI after insufficient auditory performances and only minor tinnitus reduction with CI. Audiological follow-up was carried out during a 5-year follow-up period comprising pure-tone audiometry, speech-in-quiet testing, speech-in-noise testing, tinnitus questionnaires (tinnitus questionnaire and numeric rating scale) and the HISQUI19 questionnaire. To investigate the neural substrates of tinnitus in this subject, H2O PET tomography scans were acquired in three different conditions: 1) ABI switched off which was considered as the resting-state measurement rendering the loudest possible tinnitus for the patient (ABI OFF); 2) ABI switched on causing a small suppression of tinnitus due to electrical stimulation (ABI ON); 3) ABI switched on and 70 dB SPL white noise presented directly to the external audio processor through a direct audio cable providing the maximum tinnitus suppression for the patient (NOISE). RESULTS: Subjectively the patient reported a significant tinnitus reduction after implantation which remained stable over time with a decrease in tinnitus questionnaire from grade 4 to grade 2 and a 50% reduction in the numeric rating scale (from 8 to 4) during the 5-year period. Comparing the ABI OFF and ABI ON conditions, significant increase in regional cerebral blood flow (rCBF) was observed in brain areas involved in the salience network showing already suppression of tinnitus only by electrical stimulation in the absence of auditory stimuli. The NOISE condition showed relatively decreased rCBF in the insula (as well as in the orbitofrontal cortex) as compared with the ABI OFF condition. Abnormally activated areas comprising the salience network may have been significantly suppressed by the NOISE condition both by acoustic and electrical stimulations of the auditory pathway. Moreover, the NOISE condition showed significantly decreased rCBF in the parahippocampus as compared with the ABI OFF condition. This finding supports the idea of distinct tinnitus generators depending on the amount of hearing loss. CONCLUSION: The reduction of tinnitus in the current ABI subject may be attributable to partial peripheral reafferentation-induced deactivation of the parahippocampus-based tinnitus generator as well as the salience network. Further validation is required by the use of a follow-up study with a larger number of subjects.

Magnetic resonance imaging with cochlear implants and auditory brainstem implants: Are we truly practicing MRI safety?

OBJECTIVE: Our objective is to evaluate the safety in patients with cochlear implants (CIs) and auditory brainstem implants (ABI) undergoing 1.5 Tesla (T) magnetic resonance imaging (MRI). Secondly, we want to raise awareness on CI and MRI safety, and advocate for continued improvement and advancement to minimize morbidity for our CI patients. METHODS: Retrospective case series from 2006 to 2018 at a single tertiary academic center. Data was collected on patients with CI or auditory brainstem implants undergoing MRI. Outcomes collected include demographic data, age at time of MRI, MRI characteristics, complications, CI manufacturer, and image quality. RESULTS: Eighteen patients with CI or ABI collectively underwent a total of 62 MRI scans. Five of 15 (33%) CI patients with magnet had complications: five total of 24 MRI scans (21%). Two patients had magnet removal prior to 29 MRI scans without complications. Four of five MRI-related complications were equipped with a U.S. Food and Drug Administration-approved head wrap. Three of five required a trip to the operating room to explore and reposition the CI magnet; two could not complete MRI secondary to pain. Of the complications, two were Cochlear (Sydney, Australia), two Advanced Bionics (Valencia, CA), and one MED-EL (Innsbruck, Austria). Synchrony model (MED-EL) had 0 of seven complications, with a total of 19 MRI scans, which features a freely rotating and self-aligning magnet. CONCLUSION: Our series offers a diverse number of CI manufacturers and is in accordance with other literature that CI MRI-related adverse events are occurring at an unacceptable frequency. We can promote CI MRI safety through our institutions' MRI CI patient protocols, raise awareness that diagnostic MRI benefits must outweigh CI-related complications, and advocate for continued industry technological innovation. LEVEL OF EVIDENCE: 4 Laryngoscope, 129:482-489, 2019.

Resorbable Mesh Cranioplasty Repair of Bilateral Cerebrospinal Fluid Leaks Following Pediatric Simultaneous Bilateral Auditory Brainstem Implant Surgery.

OBJECTIVE: To present a child with cochlear nerve deficiency (CND) who received simultaneous bilateral simultaneous auditory brainstem implants (BS-ABI) and subsequently presented with bilateral cerebrospinal fluid (CSF) leaks unresponsive to standard treatments. To propose a novel rigid retrosigmoid cranioplasty for treating and preventing CSF leaks in children at high risk for this complication. PATIENT: A 3.5-year-old child with CND, vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal anomalies, and limb abnormalities, coloboma, heart defect, atresia choanae, retarded growth and development, genital abnormality, and ear abnormality, Arnold Chiari malformation, previous treated tracheo-esophageal fistula underwent BS-ABI. Postoperatively, the child had recurrent bilateral retroauricular fluid collections. A standard revision procedure revealed breaches in the dural closure, migration of the auditory brainstem implantation (ABI) receiver stimulator on both sides and was unsuccessful in stopping the leak. INTERVENTIONS: Bilateral repair with free fat grafting filling the craniectomy space and two absorbable meshes of poly-L-D-lactic (PLDL) acid stabilized with PLDL pins on the surrounding cranium, one to stabilize the fat graft and one to fix the ABI receiver stimulators inside the subperiosteal pockets. MAIN OUTCOME MEASURE: CSF leak recurrence, postoperative computed tomographic (CT) scans, intra- and postoperative simultaneous electrically evoked auditory brainstem responses (EABRs). Subjective and objective assessment of ABI function. RESULTS: No postoperative CSF leaks at 60 days follow-up. EABRs and consistent behavioral responses obtained at initial mapping on both sides. CONCLUSIONS: The use of BS-ABI likely contributed to bilateral CSF leaks requiring revision surgeries in this child. Simultaneous bilateral craniotomies can put patients at risk for CSF leak. A novel cranioplasty technique employed finally proved successful in stopping the CSF leak in this case.

Initial Results of a Safety and Feasibility Study of Auditory Brainstem Implantation in Congenitally Deaf Children.

OBJECTIVE: To determine the safety and feasibility of the auditory brainstem implant (ABI) in congenitally deaf children with cochlear aplasia and/or cochlear nerve deficiency. STUDY DESIGN: Phase I feasibility clinical trial of surgery in 10 children, ages 2 to 5 years, over a 3-year period. SETTING: Tertiary children's hospital and university-based pediatric speech/language/hearing center. INTERVENTION(S): ABI implantation and postsurgical programming. MAIN OUTCOME MEASURE(S): The primary outcome measure is the number and type of adverse events during ABI surgery and postsurgical follow-up, including behavioral mapping of the device. The secondary outcome measure is access to and early integration of sound. RESULTS: To date, nine children are enrolled. Five children have successfully undergone ABI surgery and postoperative behavioral programming. Three children were screen failures, and one child is currently undergoing candidacy evaluation. Expected adverse events have been documented in three of the five children who received the ABI. One child experienced a cerebral spinal fluid leak, which resolved with lumbar drainage. One child demonstrated vestibular side effects during device programming, which resolved by deactivating one electrode. One child experienced postoperative vomiting resulting in an abdominal radiograph. Four children have completed their 1-year follow-up and have speech detection thresholds of 30 to 35 dB HL. Scores on the IT-MAIS/MAIS range from 8 to 31 (out of a total of 40), and the children are demonstrating some ability to discriminate between closed-sets words that differ by number of syllables (pattern perception). CONCLUSION: ABI surgery and device activation seem to be safe and feasible in this preliminary cohort.

Pediatric Auditory Brainstem Implant Surgery: A New Option for Auditory Habilitation in Congenital Deafness?

INTRODUCTION: The auditory brainstem implant (ABI) is a neuroprosthetic device that provides sound sensations to individuals with profound hearing loss who are not candidates for a cochlear implant (CI) because of anatomic constraints. Herein we describe the ABI for family physicians. METHODS: PubMed was searched to identify articles relevant to the ABI, as well as articles that contain outcomes data for pediatric patients (age <18 years) who have undergone ABI surgery. RESULTS: The ABI was originally developed for patients with neurofibromatosis type 2 (NF2) who become deaf from bilateral vestibular schwannomas. Over the past decade, indications for an ABI have expanded to adult patients without tumors (without NF2) who cannot receive a CI and children with no cochlea or cochlear nerve. Outcomes among NF2 ABI users are modest compared to cochlear implant patients, but recent studies from Europe suggest that some non-tumor adult and pediatric ABI users achieve speech perception. CONCLUSION: The ABI is a reasonable surgical option for children with profound hearing loss due to severe cochlear or cochlear nerve deformities. Continued prospective data collection from several clinical trials in the U.S. will provide greater understanding on long term outcomes that focus on speech intelligibility.

Pediatric Auditory Brainstem Implant Surgery.

Auditory brainstem implants (ABIs) provide auditory perception in patients with profound hearing loss who are not candidates for the cochlear implant (CI) because of anatomic constraints or failed CI surgery. Herein, the authors discuss (1) preoperative evaluation of pediatric ABI candidates, (2) surgical approaches, and (3) contemporary ABI devices and their use in the pediatric population. The authors also review the surgical and audiologic outcomes following pediatric ABI surgery. The authors' institutional experience and the nearly 200 cases performed in Europe and the United States indicate that ABI surgery in children can be safe and effective.

Trigeminal neuralgia resulting from auditory brainstem implant cable compression.

The authors report a case of neurofibromatosis Type 2 presenting with symptoms of trigeminal neuralgia refractory to medical management following placement of an auditory brainstem implant (ABI). Physical examination and history revealed trigeminal neuralgia. A 3D FIESTA (fast imaging employing steady-state acquisition) MR imaging study demonstrated compression of the trigeminal nerve by an ABI cable. After maximal medical therapy, a retrosigmoid microscopic decompression of the trigeminal nerve achieved complete symptom resolution. This is the first report of an ABI cable becoming displaced, resulting in neurovascular compression. This case demonstrates that trigeminal neuralgia can result from nonvascular compression of the trigeminal nerve.

Auditory midbrain implant: a review.

The auditory midbrain implant (AMI) is a new hearing prosthesis designed for stimulation of the inferior colliculus in deaf patients who cannot sufficiently benefit from cochlear implants. The authors have begun clinical trials in which five patients have been implanted with a single shank AMI array (20 electrodes). The goal of this review is to summarize the development and research that has led to the translation of the AMI from a concept into the first patients. This study presents the rationale and design concept for the AMI as well a summary of the animal safety and feasibility studies that were required for clinical approval. The authors also present the initial surgical, psychophysical, and speech results from the first three implanted patients. Overall, the results have been encouraging in terms of the safety and functionality of the implant. All patients obtain improvements in hearing capabilities on a daily basis. However, performance varies dramatically across patients depending on the implant location within the midbrain with the best performer still not able to achieve open set speech perception without lip-reading cues. Stimulation of the auditory midbrain provides a wide range of level, spectral, and temporal cues, all of which are important for speech understanding, but they do not appear to sufficiently fuse together to enable open set speech perception with the currently used stimulation strategies. Finally, several issues and hypotheses for why current patients obtain limited speech perception along with several feasible solutions for improving AMI implementation are presented.