Human Histology after Structure Preservation Cochlear Implantation via Round Window Insertion.

OBJECTIVES: Current surgical techniques aim to preserve intracochlear structures during cochlear implant (CI) insertion to maintain residual cochlear function. The optimal technique to minimize damage, however, is still under debate. The aim of this study is to histologically compare insertional trauma and intracochlear tissue formation in humans with a CI implanted via different insertion techniques. METHODS: One recent temporal bone from a donor who underwent implantation of a full-length CI (576°) via round window (RW) insertion was compared with nine cases implanted via cochleostomy (CO) or extended round window (ERW) approach. Insertional trauma was assessed on H&E-stained histological sections. 3D reconstructions were generated and virtually re-sectioned to measure intracochlear volumes of fibrosis and neo-ossification. RESULTS: The RW insertion case showed electrode translocation via the spiral ligament. 2/9 CO/ERW cases showed no insertional trauma. The total volume of the cochlea occupied by fibro-osseous tissue was 10.8% in the RW case compared with a mean of 30.6% (range 8.7%-44.8%, N = 9) in the CO/ERW cases. The difference in tissue formation in the basal 5 mm of scala tympani, however, was even more pronounced when the RW case (12.3%) was compared with the cases with a CO/ERW approach (mean of 93.8%, range 81% to 100%, N = 9). CONCLUSIONS: Full-length CI insertions via the RW can be minimally traumatic at the cochlear base without inducing extensive fibro-osseous tissue formation locally. The current study further supports the hypothesis that drilling of the cochleostomy with damage to the endosteum incites a local tissue reaction. LEVEL OF EVIDENCE: 4: Case-control study Laryngoscope, 134:945-953, 2024.

Thermal Effects of CO2, KTP, and Blue Lasers with a Flexible Fiber Delivery System on Vocal Folds.

OBJECTIVE: To determine the differences in thermal effects on vocal folds between four fiber-routed lasers. METHODS: In this experimental laboratory study the thermal effects of an AcuPulse Duo CO2 (CO2 AP), UltraPulse Duo CO2 (CO2 UP), KTP, and Blue laser were analyzed using a Schlieren technique on a human tissue mimicking gel model. Power, laser duration, laser fiber distance to tissue and mode (continuous wave [CW] vs pulsed [P] modes) were evaluated in varying combinations in order to compare the effects of the tested lasers and to explore the individual effect on thermal expansion and incision depth of each setting. The model was validated by comparing the results from the Schlieren model with histology of ex vivo fresh human vocal folds after laser irradiation using a selection of the same laser settings, and calculating the intraclass correlation coefficient (ICC). RESULTS: One thousand ninety-eight Schlieren experiments and 56 vocal cord experiments were conducted. In comparison with CW mode, less thermal expansion occurred in P mode in all lasers, while incisions were deeper in the CO2 and more superficial in the KTP and Blue lasers. The mean thermal expansion was found to be minimally smaller, whereas incision depth was pronouncedly smaller in the KTP and Blue compared to the CO2 lasers. Duration of laser irradiation was the most important factor of influence on thermal expansion and incision depth for all lasers in both CW and P modes. The ICC for consistency between the results of the Schlieren model and the vocal cord histology was classified from fair to excellent, except for the thermal expansion of the Blue laser, which was classified as poor. CONCLUSION: This study demonstrates important differences in thermal effects between CO2, KTP, and Blue lasers which can be explained by the different physical characteristics of the P modes and divergence of the fiber delivery system. The Schlieren imaging model is a good predictor of the relative thermal effects in vocal fold tissue. Our results can be used as a guidance for ENT surgeons using fiber-routed lasers, in order to achieve effective treatment of vocal fold lesions and prevention of functional impairment of vocal folds.

Intracochlear electrode array position and cochlear implant outcomes using the nucleus slim modiolar electrode and the extended round window approach: a follow-up study.

PURPOSE: The aim of this study was to evaluate the intracochlear position of the Slim Modiolar Electrode (SME) after insertion via the extended Round Window (eRW) approach, and to correlate this with residual hearing preservation and speech perception outcomes. METHODS: Twenty-three adult participants, consecutively implanted with the SME via the eRW approach, were included in this prospective, single-center, observational study. Electrode position was evaluated intra-operatively using X-ray fluoroscopy and TIM measurement, and post-operatively using ultra-high resolution CT. Residual hearing [threshold shift in PTA between pre- and post-operative measurement, relative hearing preservation (RHP%)] and speech perception were evaluated at 2 and 12 months after surgery. RESULTS: In each of the 23 participants, complete scala tympani positioning of the electrode array could be achieved. In one participant, an initial tip fold-over was corrected during surgery. Average age at implantation was 63.3 years (SD 13.3, range 28-76) and mean preoperative residual hearing was 81.5 dB. The average post-operative PTA threshold shift was 16.2 dB (SD 10.8) at 2 months post-operatively, corresponding with a RHP% score of 44% (SD 34.9). At 12 months, the average RHP% score decreased to 37%. Postoperative phoneme scores improved from 27.1% preoperatively, to 72.1% and 82.1% at 2 and 12 months after surgery, respectively. CONCLUSION: Use of the eRW approach results in an increased likelihood of complete scala tympani insertion when inserting the SME, with subsequent excellent levels of speech perception. However, residual hearing preservation was found to be moderate, possibly as a result of the extended round window approach, emphasizing that it is not an all-purpose approach for inserting this particular electrode array.

Ultra-High-Resolution CT to Detect Intracochlear New Bone Formation after Cochlear Implantation.

Background Histopathologic studies reported that cochlear implantation, a well-established means to treat severe-to-profound sensorineural hearing loss, may induce inflammation, fibrosis, and new bone formation (NBF) with possible impact on loss of residual hearing and hearing outcome. Purpose To assess NBF in vivo after cochlear implantation with ultra-high-spatial-resolution (UHSR) CT and its implication on long-term residual hearing outcome. Materials and Methods In a secondary analysis of a prospective single-center cross-sectional study, conducted between December 2016 and January 2018, patients with at least 1 year of cochlear implantation experience underwent temporal bone UHSR CT and residual hearing assessment. Two observers evaluated the presence and location of NBF independently, and tetrachoric correlations were used to assess interobserver reliability. In addition, the scalar location of each electrode was assessed. After consensus agreement, participants were classified into two groups: those with NBF (n = 83) and those without NBF (n = 40). The association between NBF and clinical parameters, including electrode design, surgical approach, and long-term residual hearing loss, was tested using the χ2 and Student t tests. Results A total of 123 participants (mean age ± standard deviation, 63 years ± 13; 63 women) were enrolled. NBF was found in 83 of the 123 participants (68%) at 466 of 2706 electrode contacts (17%). Most NBFs (428 of 466, 92%) were found around the 10 most basal contacts, with an interobserver agreement of 86% (2297 of 2683 contacts). Associations between electrode types and surgical approaches were significant (58 of 79 participants with NBF and a precurved electrode vs 24 of 43 with NBF and a straight electrode, P = .04; 64 of 88 participants with NBF and a cochleostomy approach vs 18 of 34 with NBF and a round window approach, P = .03). NBF was least often seen in full scala tympani insertions, but there was no significant association between scalar position and NBF (P = .15). Long-term residual hearing loss was significantly larger in the group with NBF compared with the group without NBF (mean, 22.9 dB ± 14 vs 8.6 dB ± 18, respectively; P = .04). Conclusion In vivo detection of new bone formation (NBF) after cochlear implantation is possible by using ultra-high-spatial-resolution CT. Most cochlear implant recipients develop NBF, predominately located at the base of the cochlea. NBF adversely affects long-term residual hearing preservation. © RSNA, 2021 An earlier incorrect version appeared online. This article was corrected on December 8, 2021.

Comparison Between Transimpedance Matrix (TIM) Measurement and X-ray Fluoroscopy for Intraoperative Electrode Array Tip Fold-Over Detection.

OBJECTIVE: The aim of this study was to compare Transimpedance Matrix (TIM-) measurement and X-ray fluoroscopy for the intraoperative detection of electrode array tip fold-over in cochlear implant recipients. STUDY DESIGN: Retrospective agreement study. SETTING: Tertiary referral hospital. PATIENTS: Forty-two patients (47 ears) consecutively implanted with the Slim Modiolar Electrode. INTERVENTIONS: Five raters, with different levels of clinical experience, individually retrospectively evaluated the TIM-heatmaps and X-ray fluoroscopy images of all patients included in this study for electrode array tip fold-over. MAIN OUTCOME MEASURES: Agreement between raters' individual evaluation and the diagnosis given during clinical intraoperative evaluation for both modalities, as well as the inter-method agreement between TIM-measurement and fluoroscopy, and the inter-rater agreement for both modalities. RESULTS: A tip fold-over was found in three of the forty-seven implantations (6.4%) included in this study. The average agreement between raters' evaluation and the intraoperative evaluation was 88% (Cohens κ = 0.378) for fluoroscopy and 99% (Cohens κ = 0.915) for TIM-measurement. Two raters misdiagnosed at least one tip fold-over as being correctly positioned when evaluating the fluoroscopy images (1/3 and 3/3, respectively). Each of the raters correctly detected all three tip fold-overs using the TIM-heatmaps. The inter-rater agreement for fluoroscopy was classified as "fair" (Fleiss' κ = 0.286), while the inter-rater agreement for TIM-measurement was classified as "near-perfect" (Fleiss' κ = 0.850). CONCLUSIONS: TIM-measurement has a high potential to replace X-ray fluoroscopy for intraoperatively detecting electrode array tip fold-over in cochlear implantation, especially in patients implanted with flexible, precurved arrays.

Transimpedance Matrix (TIM) Measurement for the Detection of Intraoperative Electrode Tip Foldover Using the Slim Modiolar Electrode: A Proof of Concept Study.

OBJECTIVES: The aim of this study is to report on our preliminary experience with Transimpedance Matrix (TIM)-measurement for the detection of cochlear implant electrode tip foldovers compared with intraoperative imaging in patients implanted with the slim modiolar electrode (SME). STUDY DESIGN: Proof of concept study. SETTING: Tertiary university referral center. PATIENTS: Twenty five ears (in 22 patients) implanted consecutively with the SME. INTERVENTIONS: Following cochlear implantation, intraoperative TIM-measurement and fluoroscopy were performed. One week postoperatively, the electrode position was evaluated using Computed Tomography (CT)-imaging. MAIN OUTCOME MEASURES: Electrode array tip foldover. RESULTS: Electrode array tip foldover occurred in three of the 25 cochlear implantations performed (12%). In each case, the foldover was detected by both TIM and fluoroscopy, leading to reposition and correct intracochlear placement of the array. CONCLUSIONS: TIM-measurement is a promising method for the intraoperative detection of an electrode array tip foldover. The TIM-tool with intuitive heatmap display is easy to use, fast, and readily available to clinics using TIM-software in the operating theatre.

Optimizing Settings for Office-Based Endoscopic CO2 Laser Surgery Using an Experimental Vocal Cord Model.

OBJECTIVES/HYPOTHESIS: To provide insight in the thermal effects of individual laser settings in target tissues to optimize flexible endoscopic CO2 laser surgery treatment. STUDY DESIGN: Experimental laboratory study. METHODS: Thermal effects of the CO2 laser using a fiber delivery system were visualized using the color Schlieren technique in combination with a polyacrylamide gel tissue model. Variable settings were used for emission mode, power, laser fiber distance, and laser duration, which were evaluated in every possible combination. Collateral thermal expansion and incision depth were measured. To validate the model, the results were compared to histology after CO2 laser irradiation of ex vivo human vocal cords, and the intraclass correlation coefficient was calculated. Thermal damage and incision depth were measured by a blinded pathologist. RESULTS: Of all parameters studied, duration of laser irradiation had the greatest effect on thermal expansion. Increased distance between laser tip and target tissue resulted in significantly reduced incision depth and increased thermal expansion. Pulsed emission modes led to increased incision depths. The intraclass correlation coefficient for consistency between the model setup and the ex vivo human vocal cords was classified as "fair." CONCLUSIONS: By using high-intensity pulsed lasers at minimal distance to the target tissue, exposure times and subsequent damage to surrounding tissue can be reduced. If an evaporation technique is used, lower power in continuous wave at a larger distance to the target tissue will lead to superficial but broader thermal effects. The model setup used in this study is a valid model to investigate laser-induced thermal effects in vocal cord tissue. LEVEL OF EVIDENCE: NA Laryngoscope, 130:E680-E685, 2020.