Development of a Semi-Automated Approach for the Quantification of Neuronal Cells in the Spiral Ganglion of the Whole Implanted Gerbil Cochlea, Acquired by Light-Sheet Microscopy.

INTRODUCTION: Assessing cochlear implantation's impact on cell loss and preventing post-implant cochlear damage are key areas of focus for hearing preservation research. The preservation of auditory neuronal and sensory neural hearing cells has a positive impact on auditory perception after implantation. This study aimed to provide details on a semi-automated spiral ganglion neuronal cell counting method, developed using whole implanted gerbil cochlea acquisitions with light-sheet microscopy. METHODS: Mongolian gerbils underwent right cochlear implantation with an electrode array whose silicone was loaded with dexamethasone or not and were euthanized 10 weeks after implantation. The cochleae were prepared according to a 29-day protocol, with the electrode array in place. Light-sheet microscopy was used for acquisition, and Imaris software was employed for three-dimensional analysis of the cochleas and semi-automatic quantification of spiral ganglion cells. The imaJ software was used for the manual quantification of these cells. RESULTS: Six cochleae were acquired by light-sheet microscopy, allowing good identification of cells. There was no significant difference between the mean number of spiral ganglion cells obtained by manual and semi-automatic counting (p = 0.25). CONCLUSION: Light-sheet microscopy provided complete visualization of the spiral ganglion and cell identification. The semi-automated counting method developed using Imaris software tools proved reliable and efficient and could be applied to a larger sample to assess post-cochlear implant cell damage and the efficacy of protective drugs delivered to the inner ear.

Hearing Outcomes from Gamma Knife Treatment for Intracanalicular Vestibular Schwannomas with Good Initial Hearing.

Background: The objective of this study was to describe the long-term hearing outcomes of gamma knife treatment for unilateral progressing vestibular schwannomas (VS) presenting with good initial hearing using audiologic data. Methods: A retrospective review was performed between 2010 and 2020 to select patients with progressing unilateral VS and good hearing (AAO-HNS class A) treated with stereotactic gamma knife surgery (GKS). Their audiograms were analyzed along with treatment metrics and patient data. Results: Hearing outcomes with a median follow-up of 5 years post-treatment showed statistically significant loss of serviceable hearing: 34.1% of patients maintained good hearing (AAO-HNS class A), and 56.1% maintained serviceable hearing (AAO-HNS class A and B). Non-hearing outcomes are favorable with excellent tumor control and low facial nerve morbidity. Conclusions: Hearing declines over time in intracanalicular VS treated with GKS, with a significant loss of serviceable hearing after 5 years. The mean cochlear dose and the presence of cochlear aperture obliteration by the tumor are the main statistically significant factors involved in the hearing outcomes.

Evaluation of thyroplasty with cartilage implant in young children.

OBJECTIVE: To evaluate thyroplasty with autologous cartilage implant in young children. METHODS: This retrospective study included all patients aged <10 years who underwent thyroplasty, in a tertiary care center, between 1999 and 2019 and had a postoperative follow-up at least one year later. Morphological evaluation was based on fiberoptic laryngoscopy and laryngeal ultrasound. Functional outcomes included parental evaluation of laryngeal signs by visual analogue scale and dysphonia ratings on the Grade, Roughness, Breathiness, Asthenia, and Strain scale. These assessments were performed at postoperative months 1, 6, and 12, and then annually. RESULTS: Participants were 11 patients with a median age of 26 months (8-115 months). Their median duration of progression of paralysis before surgical management was 17 months. No intra or postoperative complications were observed. Postoperative evaluation showed virtual disappearance of aspiration and chronic congestion. Voice evaluation revealed significant improvements in all patients. The long-term trend, over a median of 77 months, showed stable results in 10 cases. One patient had late-onset deterioration requiring an additional vocal fold injection. Ultrasound follow-up showed no resorption of the cartilage implant and no deformation of the thyroid ala. CONCLUSION: Pediatric thyroplasty requires technical adaptations. Use of a cartilage implant allows observation of medialization stability during the growth. These findings are particularly relevant of contraindication or failure of nonselective reinnervation.

Evaluation of the Efficacy of Dexamethasone-Eluting Electrode Array on the Post-Implant Cochlear Fibrotic Reaction by Three-Dimensional Immunofluorescence Analysis in Mongolian Gerbil Cochlea.

Cochlear implant is the method of choice for the rehabilitation of severe to profound sensorineural hearing loss. The study of the tissue response to cochlear implantation and the prevention of post-cochlear-implant damages are areas of interest in hearing protection research. The objective was to assess the efficacy of dexamethasone-eluting electrode array on endo canal fibrosis formation by three-dimensional immunofluorescence analysis in implanted Mongolian gerbil cochlea. Two trials were conducted after surgery using Mongolian gerbil implanted with dexamethasone-eluting or non-eluting intracochlear electrode arrays. The animals were then euthanised 10 weeks after implantation. The cochleae were prepared (electrode array in place) according to a 29-day protocol with immunofluorescent labelling and tissue clearing. The acquisition was carried out using light-sheet microscopy. Imaris software was then used for three-dimensional analysis of the cochleae and quantification of the fibrotic volume. The analysis of 12 cochleae showed a significantly different mean volume of fibrosis (2.16 × 108 µm3 ± 0.15 in the dexamethasone eluting group versus 3.17 × 108 µm3 ± 0.54 in the non-eluting group) (p = 0.004). The cochlear implant used as a corticosteroid delivery system appears to be an encouraging device for the protection of the inner ear against fibrosis induced by implantation. Three-dimensional analysis of the cochlea by light-sheet microscopy was suitable for studying post-implantation tissue damage.

Hearing Response Following Internal Auditory Canal Decompression in Neurofibromatosis Type 2.

BACKGROUND: Hearing response following an osteodural decompression of the internal auditory canal (IAC) is controversial. OBJECTIVE: To evaluate the course of auditory brainstem responses (ABRs) and the early hearing response during the first year following IAC decompression for small to medium-sized vestibular schwannomas occurring in neurofibromatosis type 2 (NF2). METHODS: Retrospective chart review of middle fossa craniotomy for IAC osteodural decompression in NF2-related vestibular schwannomas. RESULTS: Twelve NF2 patients were operated on from 2011 to 2016 for IAC decompression. All had NF2 according to the Manchester criteria. All had a progressive change of their ABRs documented from the diagnosis of NF2 over a mean period of 6.25 [0.36;10.9] yr. Treatment was proposed to stop hearing progression based on the speech discrimination scores (SDSs; n = 4) or for hearing maintenance (n = 8). In patients with prior hearing progression, hearing responses were observed in 3 of the 4 patients during the first year. One patient kept on progressing. In the hearing maintenance group, the SDSs remained stable. SDSs improved from 85% [20-100] to 92.5% [60-100] on average (n = 12) and from 55% [20-80] to 77.5% [50-100] in the hearing progression group (n = 4). ABRs improved in 4 patients following decompression. CONCLUSION: IAC decompression allows early objective hearing responses in select patients. We suggest that the procedure should be offered to patients with hearing progression based on their SDSs and/or associated progressive increases in their wave III and V latencies on ABRs.