Hampshire Sheep as a Large-Animal Model for Cochlear Implantation.

BACKGROUND: Sheep have been proposed as a large-animal model for studying cochlear implantation. However, prior sheep studies report that the facial nerve (FN) obscures the round window membrane (RWM), requiring FN sacrifice or a retrofacial opening to access the middle-ear cavity posterior to the FN for cochlear implantation. We investigated surgical access to the RWM in Hampshire sheep compared to Suffolk-Dorset sheep and the feasibility of Hampshire sheep for cochlear implantation via a facial recess approach. METHODS: Sixteen temporal bones from cadaveric sheep heads (ten Hampshire and six Suffolk-Dorset) were dissected to gain surgical access to the RWM via an extended facial recess approach. RWM visibility was graded using St. Thomas' Hospital (STH) classification. Cochlear implant (CI) electrode array insertion was performed in two Hampshire specimens. Micro-CT scans were obtained for each temporal bone, with confirmation of appropriate electrode array placement and segmentation of the inner ear structures. RESULTS: Visibility of the RWM on average was 83% in Hampshire specimens and 59% in Suffolk-Dorset specimens (p = 0.0262). Hampshire RWM visibility was Type I (100% visibility) for three specimens and Type IIa (> 50% visibility) for seven specimens. Suffolk-Dorset RWM visibility was Type IIa for four specimens and Type IIb (< 50% visibility) for two specimens. FN appeared to course more anterolaterally in Suffolk-Dorset specimens. Micro-CT confirmed appropriate CI electrode array placement in the scala tympani without apparent basilar membrane rupture. CONCLUSIONS: Hampshire sheep appear to be a suitable large-animal model for CI electrode insertion via an extended facial recess approach without sacrificing the FN. In this small sample, Hampshire specimens had improved RWM visibility compared to Suffolk-Dorset. Thus, Hampshire sheep may be superior to other breeds for ease of cochlear implantation, with FN and facial recess anatomy more similar to humans.

Meta-Analysis-Correlation between Spiral Ganglion Cell Counts and Speech Perception with a Cochlear Implant.

The presence of spiral ganglion cells (SGCs) is widely accepted to be a prerequisite for successful speech perception with a cochlear implant (CI), because SGCs provide the only known conduit between the implant electrode and the central auditory system. By extension, it has been hypothesized that the number of SGCs might be an important factor in CI outcomes. An impressive body of work has been published on findings from the laborious process of collecting temporal bones from CI users and counting the number of SGCs to correlate those numbers with speech perception scores, but the findings thus far have been conflicting. We performed a meta-analysis of all published studies with the hope that combining existing data may help us reach a more definitive conclusion about the relationship between SGC count and speech perception scores in adults.

Relationship between Surgically Treated Superior Canal Dehiscence Syndrome and Body Mass Index.

Objective Examine the association between body mass index (BMI) and superior canal dehiscence (SCD) among patients who have undergone surgical repair for superior canal dehiscence. Study Design Retrospective comparison study. Setting Neurotology tertiary care center. Subjects and Methods Retrospective review of consecutive adult patients evaluated at our institution for SCD syndrome between November 2006 and August 2015. A control group who underwent imaging within the same period for reasons other than SCD was also included. Patient demographics, weight, and height were examined. We performed multiple subgroup analyses to investigate the relationship of BMI, surgery vs no surgery, and correlation between patient BMI and SCD size. Results Of the 268 patients with SCD, 99 underwent surgery; 96 of these patients had complete medical records and were eligible for inclusion. Eighty-eight patients were noted to have arcuate eminence defects, and the mean BMI of this surgical cohort was 28.09 ± 5.26 kg/m2. Nonsurgically treated patients with SCD with available data (n = 94) had a mean BMI of 27.97 ± 6.95 kg/m2. A control group of 204 patients who underwent computed tomography for non-SCD-related causes was analyzed, of whom 155 had available data with a mean BMI of 27.91 ± 6.38 kg/m2. Conclusion We demonstrate that adult patients who undergo surgery for SCD are not obese (mean BMI <30), and size of dehiscence poorly correlates with BMI. Our observations call into question the proposed theory that patient weight is a risk factor for the development of symptomatic SCD involving the arcuate eminence.

Endoscopic-Assisted Repair of Superior Canal Dehiscence.

Superior canal dehiscence (SCD) is a bony defect of the superior canal that can cause vestibular and/or auditory symptoms. Surgical repair of SCD provides effective relief from symptoms, and the middle fossa craniotomy approach with binocular microscopy offers direct visualization and surgical access to the arcuate eminence. However, for SCDs located along the downsloping tegmen medial to the peak of the arcuate eminence, a direct light of sight may be obscured, rendering visualization with traditional microscopy difficult. The endoscope is the ideal adjunct in middle fossa craniotomy approach SCD surgery and offers a safe, effective means to identify and repair arcuate eminence defects hidden from microscopic view.

Characteristics of Wax Occlusion in the Surgical Repair of Superior Canal Dehiscence in Human Temporal Bone Specimens.

HYPOTHESIS: Superior canal dehiscence (SCD) repair using surgical bone wax may result in variable outcomes if large wax volumes are applied. BACKGROUND: SCD is a disorder characterized by a pathologic defect in the bony labyrinth of the superior semicircular canal (SSC), resulting in vestibular and/or auditory symptoms. Repair of SCD using bone wax can provide symptomatic relief, but surgical outcomes are variable. These observations may be associated with the inconsistency in the position and extension of intralabyrinthine bone wax during surgical repair. METHODS: A pathological model of SCD was created using cadaveric human temporal bones and a microdrill. Defects in the arcuate eminence 0.5 to 3.5  mm in length were repaired by surgical occlusion with bone wax. The volume of wax used in the repair was quantified. The position of bone wax was evaluated by direct visualization and imaging (computed tomography [CT]). To visualize wax on CT, specimens were repaired using radiopaque wax. RESULTS: Exceedingly small volumes of bone wax (3.0-5.0  mm2) reliably occluded the canal lumen. Multiple wax applications resulted in extension into the common crus and ampulla. The length of this extension was related to the number of applications. CONCLUSIONS: Repair of SCD with bone wax occludes the bony defect completely in most patients. Wax can extend along the lumen of the superior canal beyond the limits of the dehiscence to reach the sensory neuroepithelium of the vestibular end organs. Limiting the number of wax applications is essential to avoid inadvertent injury to the delicate neurosensory systems.

Benign paroxysmal positional vertigo commonly occurs following repair of superior canal dehiscence.

OBJECTIVES/HYPOTHESIS: Repair of superior canal dehiscence (SCD) often results in the resolution of preoperative auditory and vestibular symptoms; however, many patients experience dizziness in the postoperative period. Postoperative dizziness may be the result of new-onset benign paroxysmal positional vertigo (BPPV). This study aims to investigate the prevalence of BPPV before and following SCD repair. STUDY DESIGN: Retrospective chart review at a tertiary care center. METHODS: Electronic medical records were reviewed for patients with a diagnosis of SCD syndrome (SCDS) between January 2002 and May 2015. Collected information included demographic data, incidence of BPPV diagnosed by Dix-Hallpike maneuver before and following surgery, operative technique, repair material, and the duration of time to BPPV onset. RESULTS: A total of 180 patients with a diagnosis of SCDS were identified: 84 patients underwent surgery (operated subjects) and 96 were observed (nonoperated, control group). In operated subjects, 20 of 84 (23.8%) developed BPPV following SCD repair versus 6.2% of nonoperated (P < 0.005). Benign paroxysmal positional vertigo lateralized to the operated side in all but one subject whose laterality was unknown (P < 0.0001). There were no associations of BPPV with surgical approach (P = 0.50) or repair material (P = 0.33). The majority of subjects (58%) were diagnosed with BPPV within 3 months of surgery. CONCLUSION: New-onset BPPV occurs commonly after SCD repair and may be the result of mobilized otoliths from inner ear pressure changes. Although the exact etiology of post-SCD repair BPPV remains unknown, postoperative dizziness is important to discuss with patients during preoperative counseling. LEVEL OF EVIDENCE: 4. Laryngoscope, 126:2092-2097, 2016.

Periodic botulinum toxin injections for paradoxical vocal fold motion in a child with cerebral palsy: a case study.

We describe an unusual case of paradoxical vocal fold motion in a child with cerebral palsy. Clinically, the child presented with mild stridor, which worsened over months, eventually requiring emergency intubation. After an unsuccessful trial of medical management, microlaryngoscopy revealed abnormal adduction of the vocal folds during inspiration. This was successfully treated with periodic type A botulinum toxin injections to the vocal folds, sparing the child from tracheostomy.