Lane, John I.

Objective To describe the development, implementation, and validation of a radiology-administered protocol to obtain magnetic resonance imaging (MRI) in patients with cochlear implants and auditory brainstem implants without magnet removal. Study Design Retrospective review and description of novel care pathway. Methods A radiology-administered protocol was designed based on careful input from the radiology safety committee and neurotology. Radiology technologist training modules, consent instructions, patient educational material, clinical audits, and other safeguards were implemented, with samples provided in this report. The primary outcomes measured included instances of magnet displacement during MRI and premature termination of MRI studies secondary to pain. Results Between June 19, 2018, and October 12, 2021, 301 implanted ears underwent MRI without magnet removal, including 153 devices housing diametric MRI-conditional magnets, and 148 implants with conventional axial (i.e., nondiametric) magnets. Among cases with diametric MRI-conditional magnets, all studies were completed without magnet dislodgement or need to terminate imaging early due to pain. Among cases with conventional axial (nondiametric) magnets, 29 (19.6%) MRI studies were stopped prematurely secondary to pain or discomfort; the overall rate of this event was 9.6% (29 of 301) among the entire study cohort. In addition, 6.1% (9 of 148) experienced confirmed magnet displacement despite headwrap placement; the overall rate among all cases was 3.0% (9 of 301). Eight of these patients received successful external magnet reseating through manual pressure on the external scalp without surgery, and one required surgical replacement of the magnet in the operating room. There were no documented instances of hematoma, infection, device or magnet extrusion, internal device movement (i.e., gross receiver-stimulator migration), or device malfunction in this cohort related to MRI. Conclusions We present the successful implementation of a radiology-administered protocol designed to streamline care for cochlear implant and auditory brainstem implant recipients who require MRI and ease clinical demands for otolaryngology providers. Examples of resources developed, including a process map, radiology training modules, consent instructions, patient educational materials, clinical audit, and other procedural safety measures are provided so interested groups may consider adapting and implementing related measures according to need.

OBJECTIVE Preoperative differentiation of facial nerve schwannoma (FNS) from vestibular schwannoma (VS) can be challenging, and failure to differentiate between these two pathologies can result in potentially avoidable facial nerve injury. This study presents the combined experience of two high-volume centers in the management of intraoperatively diagnosed FNSs. The authors highlight clinical and imaging features that can distinguish FNS from VS and provide an algorithm to help manage intraoperatively diagnosed FNS. METHODS Operative records of 1484 presumed sporadic VS resections between January 2012 and December 2021 were reviewed, and patients with intraoperatively diagnosed FNSs were identified. Clinical data and preoperative imaging were retrospectively reviewed for features suggestive of FNS, and factors associated with good postoperative facial nerve function (House-Brackmann [HB] grade ≤ 2) were identified. A preoperative imaging protocol for suspected VS and recommendations for surgical decision-making following an intraoperative FNS diagnosis were created. RESULTS Nineteen patients (1.3%) with FNSs were identified. All patients had normal facial motor function preoperatively. In 12 patients (63%), preoperative imaging demonstrated no features suggestive of FNS, with the remainder showing subtle enhancement of the geniculate/labyrinthine facial segment, widening/erosion of the fallopian canal, or multiple tumor nodules in retrospect. Eleven (57.9%) of the 19 patients underwent a retrosigmoid craniotomy, and in the remaining patients, a translabyrinthine (n = 6) or transotic (n = 2) approach was used. Following FNS diagnosis, 6 (32%) of the tumors underwent gross-total resection (GTR) and cable nerve grafting, 6 (32%) underwent subtotal resection (STR) and bony decompression of the meatal facial nerve segment, and 7 (36%) underwent bony decompression only. All patients undergoing subtotal debulking or bony decompression exhibited normal postoperative facial function (HB grade I). At the last clinical follow-up, patients who underwent GTR with a facial nerve graft had HB grade III (3 of 6 patients) or IV facial function. Tumor recurrence/regrowth occurred in 3 patients (16%), all of whom had been treated with either bony decompression or STR. CONCLUSIONS Intraoperative diagnosis of an FNS during a presumed VS resection is rare, but its incidence can be reduced further by maintaining a high index of suspicion and undertaking further imaging in patients with atypical clinical or imaging features. If an intraoperative diagnosis does occur, conservative surgical management with bony decompression of the facial nerve only is recommended, unless there is significant mass effect on surrounding structures.

Abstract Background and Purpose Artifact from cochlear implant electrodes degrades image resolution on CT. Here, we describe the use of coregistered pre‐ and postoperative CT images to reduce metallic artifact from the electrodes to assess its position more accurately within the cochlear lumen. Methods Pre‐ and postoperative CTs were reviewed after coregistration/overlay of both exams. Images were evaluated by two neuroradiologists for scalar location of electrodes tip (± scalar translocation), tip fold over, and angular depth of insertion. Results Thirty‐four patients were included in the final cohort. Transscalar migration was present in three (8.8%) cases (one case demonstrated tip fold over), with initial disagreement regarding transscalar migration in 1 out of 34 patients (2.9%). Agreement regarding depth of insertion was present in 31 (91.1%) cases. Five‐point Likert scales were used to compare the ability to resolve the proximity of electrodes to the lateral/outer cochlear wall without and with overlay, which is a qualitative measure of artifact from the array. Likert scores showed definitive benefit of metal artifact reduction using overlayed images with an average score of 4.34. Conclusion This study demonstrates a novel technique of using fused coregistration of pre‐ and postoperative CTs for the purpose of artifact reduction/electrode localization. It is anticipated that this technique will permit more accurate localization of the electrodes for improvement in surgical technique and electrode array design.

Objective Large vestibular aqueduct (LVA) is the most common inner ear dysplasia identified in patients with hearing loss. Our objective was to systematically quantify LVA morphologies and correlate imaging findings with established audiometric outcomes. Study Design Retrospective review. Setting Tertiary referral center. Patients Patients with large vestibular aqueduct identified radiographically, with or without hearing loss. Intervention(s) Diagnostic only. Main Outcome Measure(s) Vestibular aqueduct (VA) width at midpoint, width at external aperture, and length were measured on cross-sectional imaging. Morphology was classified as type I (borderline), type II (tubular), or type III (funneled). Audiometric endpoints included air/bone conduction, pure tone averages, and air-bone gaps at 250 and 500 Hz. Statistical associations were evaluated using linear regression models, adjusted for age at first audiogram and sex. Results One hundred seventeen patients (197 ears) were included, with mean age at first audiogram of 22.2 years (standard deviation, 21.7 yr). Imaging features associated with poor audiometric outcomes were increasing VA width at midpoint and external aperture, decreasing VA length, dilated extraosseous endolymphatic sac, cochleovestibular malformations, and increasing VA type (III > II > I). Conclusions Quantitative LVA measurements and a standardized morphologic classification system aid in prediction of early audiometric endpoints.

AbstractObjectiveTo characterize normative adult ranges for cochlear promontory thickness relevant to the development of subendosteal and transpromontory electrodes to rehabilitate various neurotologic disorders.PatientsAdults (≥18 years).InterventionIn vivo radiologic assessment using a 192‐slice CT scanner (Force‐192; Siemens Healthcare) with ultrahigh‐resolution scan mode combined and iterative reconstruction.Main Outcome MeasureCochlear promontory thickness.ResultsAmong 48 included patients (96 ears), the mean (SD) age was 56 (18) years (range 25–94) and included 25 (52%) women. Of that 12 patients (25%) had osteopenia (n = 6) or osteoporosis (n = 6). The mean (SD) body mass index was 28 (5) kg/m2. The mean (SD) promontory thickness for the 96 temporal bones under study was 1.22 (0.24) mm (range 0.55–1.85). There was not a statistically significant association between age and promontory thickness (correlation coefficient .08; p = .44). Promontory thickness was significantly greater for men than women (mean 1.28 vs. 1.17 mm; p = .03) and increased with increasing body mass index (correlation coefficient .30; p = .004). Last, promontory thickness was significantly less for patients with osteopenia or osteoporosis compared with those without these conditions (mean 1.09 vs. 1.27 mm; p = .002).ConclusionsCochlear promontory thickness can vary by almost 1.5 mm across patients and is significantly associated with patient sex, body mass index, and comorbid osteopenia/osteoporosis. Subendosteal and transpromontory electrode placement techniques must account for this degree of variability.Level of EvidenceIV

Background and Purpose After cochlear implantation, metallic artifact can obscure nearby structures on CT images, which is problematic in patients with facial nerve stimulation (FNS). This study evaluated the usefulness of co-registered pre- and post-operative examinations to evaluate the cochlear implant and adjacent structures. Materials and Methods A retrospective review was completed of consecutive patients that underwent CT imaging of the temporal bone before and after placement of a cochlear implant. Two blinded neuroradiologists independently reviewed all available examinations. All examinations were assessed for the presence or absence of dehiscence of the osseous ridge between the cochlea and facial nerve canal (FNC). Pre-operative and fused pre- and post-operative examinations were compared in their ability to visualize the osseous ridge using a 5-point Likert scale (ranging from 1 = unfused images were substantially superior to 5 = fused images were substantially superior). The electrode closest to the FNC were noted. Results Of 34 included patients, 13 (38.2%) were female and 21 (61.8%) were male; average age was 72.2. Seven patients (20.6%) had frank dehiscence between the cochlea and FNC. Fused images were superior to the post-operative study alone for assessing the integrity of the osseous partition between the cochlea and FNC and for reducing artifact from the electrode array (average Likert scores for both reviewers were 4.4 and 4.7). There was good agreement between reviewers in noting electrode closest to the FNC (concordance correlation coefficient=0.82). Conclusions Following cochlear implantation, co-registered pre- and post-operative CT images are superior to conventional images in assessing the anatomic relationship between the cochlea and FNC.

AbstractObjectiveDescribe the presentation and management strategy for patients with symptomatic foramen of Huschke (FH).PatientsAdults with persistent FH confirmed on imaging.InterventionsDiagnosis and management of symptomatic persistent FH.Main outcome measureResolution of otologic symptoms.ResultsA total of four patients with symptomatic, radiographically‐confirmed persistent FH were included. The majority of patients endorsed otalgia (n = 4) and otorrhea (n = 3), and only one patient was noted to have a conductive hearing loss. All patients were noted to have dynamic movement of an external auditory canal mass with mandible manipulation on examination, and all patients had an identifiable fistula on imaging. Patients underwent surgical intervention, including both preauricular (n = 2) and transcanal (n = 2) approaches, and all endorsed symptomatic resolution after convalescence.ConclusionsPersistent FH remains an uncommon and potentially underrecognized cause of otologic symptoms. Diagnosis requires a high index of suspicion, and one must rely on both key examination findings and imaging to confirm this diagnosis. In appropriately selected patients, surgical intervention can provide durable symptomatic resolution.Level of evidenceIV