Scala Vestibuli Research Articles

Effects of Varying Laser Parameters During Laser Stapedotomy on Intracochlear Pressures.

Sensorineural hearing loss is a known complication of stapes surgery. We previously showed that laser stapedotomy can result in intracochlear pressures that are comparable to high sound pressure levels. Optimizing laser settings to those that correspond with the lowest pressure changes may mitigate risk for postoperative hearing loss. Here we quantify the effects of various laser parameters on intracochlear pressures and test the hypothesis that intracochlear pressure changes are proportional to the laser energy delivered. Basic and translational science. Cadaveric dissection and basic science laboratory. Cadaveric human heads underwent mastoidectomies. Intracochlear pressures were measured via fiber-optic pressure probes placed in scala vestibuli and tympani. Pulses of varied stimulus power and duration from a 980-nm diode laser were applied to the stapes footplate. Sustained high-intensity pressures were observed in the cochlea during all laser applications. Observed pressure magnitudes increased monotonically with laser energy and rose linearly for lower stimulus durations and powers, but there was increased variability for laser applications of longer duration (200-300 ms) and/or higher power (8 W). Results confirm that significant pressure changes occur during laser stapedotomy, which we hypothesize may cause injury. Overall energy delivered depends predictably on duration and power, but surgeons should use caution at the highest stimulus levels and longest pulse durations due to the increasing variability in intracochlear pressure under these stimulus conditions. While the risk to hearing from increased intracochlear pressures from laser stapedotomy remains unclear, these results affirm the need to optimize laser settings to avoid unintended injury.

Morphological characterization of Mast cells in the cochlea during postnatal rodent development

Mast cells (MC) are immune cells of hematopoietic origin widely distributed in the mammalian body's connective tissue. Their activity plays a potential immunoregulatory role associated with allergic reactions, autoimmune, cardiovascular, and neuronal diseases. Previously, the inner ear‐related MCs were described in the endolymphatic sac. However, the presence of MCs in the mammalian cochlea was not yet investigated.Here, we demonstrate for the first time that the MCs are present in the healthy cochlea of C57BL/6 mice and Wistar rats. Using histochemistry and immunohistochemistry on the cryo‐/paraffine sections of the whole cochlea and cochlea explants, we detected MCs in the modiolus, spiral ligament, scala vestibuli, and occasionally in scala tympani. The identified MCs expressed various MC‐specific markers: cKit/CD117, chymase, tryptase, and FcεRIa. Quantitative analysis demonstrated a significant decrease in the number of MCs during the postnatal development, resulting in only a few MCs present in the cochlea of rats and mice. In addition, 24h incubation of the cochlear explant with 40 µM of cisplatin lead to a significant reduction of MC numbers.The presence of MCs in the cochlea may shed new light on postnatal maturation of the auditory periphery and possible involvement in cisplatin ototoxicity. Currently, our findings expand the knowledge about the physiology and pathology of the auditory periphery.Considering the pivotal role of MCs in inflammation, future functional studies should explain this new basic knowledge and translate it into clinical application.

Simulation-Based Study on Round Window Atresia by Using a Straight Cochlea Model with Compressible Perilymph

The sound stimulus received by the pinna is transmitted to the oval window of the inner ear via the outer ear and middle ear. Assuming that the perilymph in the scala vestibuli and scala tympani is compressible, we report that the sound wave generated in the cochlea due to the vibration of the oval window can be expressed by the combination of even and odd symmetric sound wave modes. Based on this new approach, this paper studies the cause of hearing deterioration in the lower frequency region seen in round window atresia from the viewpoint of cochlear acoustics. Round window atresia is an auditory disease in which the round window is ossified and its movement is restricted. Using the finite element method, a round window atresia model was designed and the acoustic behavior of the round window was discussed corresponding to the level of disease. From this, we report that the healthy round window works as a free-end reflector to the incident sound waves, but it also works as a fixed-end reflector in the case of round window atresia. Next, we incorporated the round window atresia model into a cochlear model and performed a simulation in order to determine the acoustic aspects of the cochlea as a whole. The simulation results indicate that hearing deterioration occurs in a lower frequency range, which is also coincident with the clinical reports (hearing deterioration of approximately 10 to 20 dB below 4000 Hz). Finally, we explain that the cause of hearing deterioration due to round window atresia is considered to be the even sound wave mode enlarging due to the fixed-end reflection at the ossified round window, and, as a result, the odd sound wave mode that generates the Békésy’s traveling wave on a basilar membrane is significantly weakened.

Contribution of Even/Odd Sound Wave Modes in Human Cochlear Model on Excitation of Traveling Waves and Determination of Cochlear Input Impedance

Based on the Navier–Stokes equation for compressible media, this work studies the acoustic properties of a human cochlear model, in which the scala vestibuli and scala tympani are filled with compressible perilymph. Since the sound waves propagate as a compression wave in perilymph, this model can precisely handle the wave–based phenomena. Time domain analysis showed that a sound wave (fast wave) first propagates in the scala vestibuli and scala tympani, and then, a traveling wave (slow wave) is generated by the sound wave with some delay. Detailed studies based on even and odd mode analysis indicate that an odd mode sound wave, that is, the difference in the sound pressures between the scala vestibuli and scala tympani, excites the Békésy’s traveling wave, while an even mode sound determines the input impedance of the cochlea.

Imaging Analysis of Patients With Meniere's Disease Treated With Endolymphatic Sac-Mastoid Shunt Surgery.

Objective: Endolymphatic sac surgery is effective in treating intractable Meniere's disease (MD), but the underlying mechanism is still unknown. Our study investigated the mechanism by which endolymphatic sac-mastoid shunt (EMS) surgery is effective in treating MD by means of imaging.Methods: The experiment included 19 patients with intractable MD who underwent 3D-fluid-attenuated inversion recovery (FLAIR) MRI with a 3-Tesla unit 6 h after intravenous administration of gadolinium, before EMS, and 2 years after the surgery. The enhanced perilymphatic space in the bilateral cochlea, vestibule, and canals was visualized and compared with that in the endolymphatic space by quantitatively scoring the scala vestibuli of the cochlea and by measuring the developing area of the vestibules quantitatively.Results: Gadolinium was present in the perilymph of the inner ear in the cochlea, vestibules, and canals of all patients. At the 2-year follow-up, 14 (73.68%) patients had vertigo control. Both before and 2 years after surgery, significant differences were observed in the scala vestibuli scores and the area of vestibular perilymph between the affected and healthy sides. The scala vestibuli scores and the area of vestibular perilymph, however, did not differ when comparing them before and after surgery.Conclusions: According to our results, endolymphatic hydrops was not significantly reduced by surgery. The mechanism by which EMS controls vertigo might be unrelated to the improvement in hydrops.

Automatic Segmentation of Intracochlear Anatomy in MR Images Using a Weighted Active Shape Model.

There is evidence that cochlear MR signal intensity may be useful in prognosticating the risk of hearing loss after middle cranial fossa (MCF) resection of acoustic neuroma (AN), but the manual segmentation of this structure is difficult and prone to error. This hampers both large-scale retrospective studies and routine clinical use of this information. To address this issue, we present a fully automatic method that permits the segmentation of the intra-cochlear anatomy in MR images, which uses a weighted active shape model we have developed and validated to segment the intra-cochlear anatomy in CT images. We take advantage of a dataset for which both CT and MR images are available to validate our method on 132 ears in 66 high-resolution T2-weighted MR images. Using the CT segmentation as ground truth, we achieve a mean Dice (DSC) value of 0.81 and 0.79 for the scala tympani (ST) and the scala vestibuli (SV), which are the two main intracochlear structures.Clinical Relevance- The proposed method is accurate and fully automated for MR image segmentation. It can be used to support large retrospective studies that explore relations between MR signal in preoperative images and outcomes. It can also facilitate the routine and clinical use of this information.

Histopathologic Analysis of Temporal Bones With Otosclerosis Following Cochlear Implantation.

Analyze changes in osteoneogenesis and fibrosis following cochlear implant (CI) surgery in patients with otosclerosis and compare differences based on insertion technique. When advanced otosclerotic disease extends to the otic capsule, severe and profound sensorineural hearing loss necessitates consideration of a cochlear implant. Histopathological analysis of the human temporal bone after implantation in the patient with otosclerosis may reveal important variables that predict CI success. Histopathological evaluation of archival human temporal bones from subjects with a history of CI for cochlear otosclerosis. A total of 17 human temporal bones (HTB) were analyzed, 13 implanted, and 4 contralateral non-implanted controls. Histopathological studies revealed extensive osteoneogenesis and fibrosis which was more prominent at the cochleostomy insertion site in the basal turn of the cochlea often obliterating the scala tympani in the basal turn, and in some cases extending to the scala media and scala vestibuli. Cochlear hydrops was nearly universal in these cases. This contrasted with the round window insertion, which exhibited minimal osteoneogenesis within the cochlear duct. In addition, in the contralateral, unimplanted control ears, there was otosclerosis at the stapes footplate, fissula ante fenestrum but no osteoneogenesis within the cochlear duct. Cochleostomy approach to CI insertion in otosclerosis patients is associated with significant fibrosis, osteoneogenesis, and cochlear hydrops. A round window insertion technique can be utilized to help minimize these histopathologic findings whenever feasible.

Meniere’s attack – a volume or pressure phenomenon?

Meniere’s disease (MD) still raises since its discovery in 1860 pathophysiological and etiopathogenical issues. The main pathophysiological feature that has emerged for decades is an anatomic one, the endolymphatic hydrops (EH), defined by the inflation of the endolymphatic part of the membranous labyrinth. However, the causal relationship between EH and MD has not been proven. Several attempts have been achieved in animals to induce EH. The best known is the blockage of the vestibular duct, which causes a chronic volume inflation of the endolymphatic part. This model is characterized by the discrepancy between electrophysiological findings and scala media inflation. Pressure measurements vary among studies. The endolymphatic infusion model, which attempts to model the acute clinical picture of MD consistently shows pressure equilibration between the endolymphatic and perilymphatic compartments, and rapid recovery of the electrophysiological finding once the injection is stopped.

High-Molecular-Weight Hyaluronic Acid Vehicle Can Deliver Gadolinium Into the Cochlea at a Higher Concentration for a Longer Duration: A 9.4-T Magnetic Resonance Imaging Study.

Intratympanic (IT) gadolinium (Gd) injection is one method of delivering Gd into the inner ear to evaluate the amount of endolymphatic hydrops (EH) using magnetic resonance imaging (MRI). As Gd is usually prepared in a fluid form mixed with saline, Gd injected into the middle ear drains easily through the Eustachian tube within several hours. High-molecular-weight (hMW) hyaluronic acid (HA) is an ideal vehicle for IT Gd due to its viscous and adhesive properties. The present study was performed to elucidate whether novel hMW HA is superior to conventional HA in delivering Gd into the inner ear in the short term. The second aim was to verify the long-term Gd delivery efficiency of hMW HA compared to the standard-of-care vehicle (saline). IT Gd injection and 3D T1-weighted MRI were performed in 13 rats. For the short-term study (imaging after 1, 2, and 3 h), the left ear was treated with hMW HA+Gd and the right ear with conventional HA+Gd. For the long-term study (imaging after 1, 2, 3, and 4 h, 1 – 3 days, and 7 – 10 days), the left ear was treated with hMW HA+Gd and the right ear with saline+Gd. Signal intensities (SIs) in the scala tympani (ST) and scala vestibuli (SV) were quantified. Compared to conventional HA, signal enhancement was 2.3 – 2.4 times greater in the apical and middle turns after hMW HA+Gd injection (SV at 1 h). In comparison to the standard-of-care procedure, the SI was not only greater in the short term but the higher SI also lasted for a longer duration. On days 7 – 10 after IT Gd delivery, the SI in the basal turn was 1.9 – 2.1 times greater in hMW HA+Gd-treated ears than in saline IT Gd-treated ears. Overall, hMW HA may be a useful vehicle for more efficient IT Gd delivery. Gd enhancement in the cochlea improved approximately two-fold when hMW HA was used. In addition, this greater enhancement lasted for up to 7 – 10 days. Repeated MRI of EH may be possible for several days with a single IT hMW HA+Gd delivery.

Round Window Reinforcement-Induced Changes in Intracochlear Sound Pressure

Introduction: The round window membrane (RWM) acts as a pressure-relieving membrane for incompressible cochlear fluid. The reinforcement of the RWM has been used as a surgical intervention for the treatment of superior semicircular canal dehiscence and hyperacusis. The aim of this study was to investigate how RWM reinforcement affects sound pressure variations in the cochlea. Methods: The intracochlear sound pressure (ICSP) was simultaneously measured in the scala tympani (ST) and scala vestibuli (SV) of cadaveric human temporal bones (HTBs) in response to acoustic stimulation for three RWM reinforcement materials (soft tissue, cartilage, and medical-grade silicone). Results: The ICSP in the ST was significantly increased after RWM reinforcement for frequencies below 2 kHz. Between 400 and 600 Hz, all three materials demonstrated the highest median pressure increase. The higher the RWM stiffness, the larger the pressure increase: silicone (7 dB) < soft tissue (10 dB) < cartilage (13 dB). The ICSP in the SV was less affected by reinforcement. The highest median pressure increase was 3 dB. The experimental findings can be explained with numerical models of cochlear mechanics. Discussion and conclusions: RWM reinforcement increases the sound pressure in ST at lower frequencies but only has a minor influence on the SV pressure.

RAT COCHLEA CONTINUES TO DEVELOP AFTER BIRTH

Introduction: The ear, originates from the ectoderm, exhibits a complex structure that differs from species to species in terms of development. Objectives: This study was conducted to describe the prenatal and postnatal development process of the organ of Corti in the iner ear using light microscopy. Methods: In this study, Wistar Albino rats were used. The rats were divided into two groups as prenatal and postnatal groups. Prenatal groups consisting of embryos on day 17, 19, 21 and postnatal groups consisting of pups on days 1, 5, 10 and 15. The rats were sacrificed to investigate the cochleas by light microscopy. Results: The lumen of the cochlear tunnel was lined with pseudostratified columnar epithelia throughout the prenatal period. The cochlear tunnel was not divided into scala media, scala tympani and scala vestibuli in the embryonic sections. Organ of corti hasn’t taken its final form until postnatal day 15. Conclusion: In rats, formation of organ of Corti is completed in postnatal 15 day. Pups of rats are not able to hear in the embronic and early postnatal life.

Detection of Translocation of Cochlear Implant Electrode Arrays by Intracochlear Impedance Measurements.

Objectives:Misplacement of the electrode array is associated with impaired speech perception in patients with cochlear implants (CIs). Translocation of the electrode array is the most common misplacement. When a CI is translocated, it crosses the basilar membrane from the scala tympani into the scala vestibuli. The position of the implant can be determined on a postoperative CT scan. However, such a scan is not obtained routinely after CI insertion in many hospitals, due to radiation exposure and processing time. Previous studies have shown that impedance measures might provide information on the placement of the electrode arrays. The electrode impedance was measured by dividing the plateau voltage at the end of the first phase of the pulse by the injected current. The access resistance was calculated using the so-called access voltage at the first sampled time point after the start of the pulse divided by the injected current. In our study, we obtained the electrode impedance and the access resistance to detect electrode translocations using electrical field imaging. We have investigated how reliably these two measurements can detect electrode translocation, and which method performed best.Design:We calculated the electrode impedances and access resistances using electrical field imaging recordings from 100 HiFocus Mid-Scala CI (Advanced Bionics, Sylmar, CA) recipients. We estimated the normal values of these two measurements as the baselines of the implant placed in the cochlea without translocation. Next, we calculated the maximal electrode impedance deviation and the maximal access-resistance deviation from the respective baselines as predictors of translocation. We classified these two predictors as translocations or nontranslocations based on the bootstrap sampling method and receiver operating characteristics curves analysis. The accuracy could be calculated by comparing those predictive results to a gold standard, namely the clinical CT scans. To determine which measurement more accurately detected translocation, the difference between the accuracies of the two measurements was calculated.Results:Using the bootstrap sampling method and receiver operating characteristics–based optimized threshold criteria, the 95% confidence intervals of the accuracies of translocation detections ranged from 77.8% to 82.1% and from 89.5% to 91.2% for the electrode impedance and access resistance, respectively. The accuracies of the maximal access-resistance deviations were significantly larger than that of the maximal electrode impedance deviations. The location of the translocation as predicted by the access resistance was significantly correlated with the result derived from the CT scans. In contrast, no significant correlation was observed for the electrode impedance.Conclusions:Both the electrode impedance and access resistance proved reliable metrics to detect translocations for HiFocus Mid-Scala electrode arrays. The access resistance had, however, significantly better accuracy and it also reliably detected the electrode-location of translocations. The electrode impedance did not correlate significantly with the location of translocation. Measuring the access resistance is, therefore, the recommended method to detect electrode-array translocations. These measures can provide prompt feedback for surgeons after insertion, improving their surgical skills, and ultimately reducing the number of translocations. In the future, such measurements may allow near-real-time monitoring of the electrode array during insertion, helping to avoid translocations.

Insertion trauma of a new cochlear implant electrode: evaluated by histology in fresh human temporal bone specimens

Background Combining acoustic and electrical stimulation has been successfully used in patients with low-frequency residual hearing. Electrode insertion trauma, such as electrode translocation could result in loss of residual hearing. Objectives The aim of the study is to evaluate the LCI-20PI electrode array insertion trauma to the intra-cochlear structures in fresh human temporal bone specimens. Materials and methods The LCI-20PI electrode arrays were inserted into scalae tympani through round window membrane in 10 cochleae from ten fresh human cadavers. The intracochlear trauma was evaluated histologically by a scale of 0–4: 0 – no observable trauma, 1 – elevation of basilar membrane, 2 – rupture of basilar membrane or spiral ligament, 3–dislocation into scala vestibuli and 4 – fracture of modiolus or osseous spiral lamina. The insertion depth was measured by radiography. Results Histological results revealed no observable trauma in seven specimens; basal membrane elevation and rupture in two specimens; the electrode array misled into scala vestibuli in one specimen. The insertion depth varied from 228° to 288°. Conclusions and significance The insertion of the LCI-20PI electrode arrays caused no trauma in the majority of the fresh temporal bone specimens. No translocation of the electrode arrays from the scala tympani to the scala vestibuli was observed.

Recommended standardized anatomic terminology of the posterior female pelvis and vulva based on a structured medical literature review

Anatomic terminology in both written and verbal forms has been shown to be inaccurate and imprecise. Here, we aimed to (1) review published anatomic terminology as it relates to the posterior female pelvis, posterior vagina, and vulva; (2) compare these terms to "Terminologia Anatomica," the internationally standardized terminology; and (3) compile standardized anatomic terms for improved communication and understanding. From inception of the study to April 6, 2018, MEDLINE database was used to search for 40 terms relevant to the posterior female pelvis and vulvar anatomy. Furthermore, 11 investigators reviewed identified abstracts and selected those reporting on posterior female pelvic and vulvar anatomy for full-text review. In addition, 11 textbook chapters were included in the study. Definitions of all pertinent anatomic terms were extracted for review. Overall, 486 anatomic terms were identified describing the vulva and posterior female pelvic anatomy, including the posterior vagina. "Terminologia Anatomica" has previously accepted 186 of these terms. Based on this literature review, we proposed the adoption of 11 new standardized anatomic terms, including 6 regional terms (anal sphincter complex, anorectum, genital-crural fold, interlabial sulcus, posterior vaginal compartment, and sacrospinous-coccygeus complex), 4 structural terms (greater vestibular duct, anal cushions, nerve to the levator ani, and labial fat pad), and 1 anatomic space (deep postanal space). In addition, the currently accepted term rectovaginal fascia or septum was identified as controversial and requires further research and definition before continued acceptance or rejection in medical communication. This study highlighted the variability in the anatomic nomenclature used in describing the posterior female pelvis and vulva. Therefore, we recommended the use of standardized terminology to improve communication and education across medical and anatomic disciplines.

Forward and Reverse Middle Ear Transmission in Gerbil with a Normal or Spontaneously Healed Tympanic Membrane.

Tympanic membranes (TM) that have healed spontaneously after perforation present abnormalities in their structural and mechanical properties; i.e., they are thickened and abnormally dense. These changes result in a deterioration of middle ear (ME) sound transmission, which is clinically presented as a conductive hearing loss (CHL). To fully understand the ME sound transmission under TM pathological conditions, we created a gerbil model with a controlled 50% pars tensa perforation, which was left to heal spontaneously for up to 4weeks (TM perforations had fully sealed after 2weeks). After the recovery period, the ME sound transmission, both in the forward and reverse directions, was directly measured with two-tone stimulation. Measurements were performed at the input, the ossicular chain, and output of the ME system, i.e., at the TM, umbo, and scala vestibuli (SV) next to the stapes. We found that variations in ME transmission in forward and reverse directions were not symmetric. In the forward direction, the ME pressure gain decreased in a frequency-dependent manner, with smaller loss (within 10dB) at low frequencies and more dramatic loss at highfrequency regions. The loss pattern was mainly from the less efficient acoustical to mechanical coupling between the TM and umbo, with little changes along the ossicular chain. In the reverse direction, the variations in these ears are relatively smaller. Our results provide detailed functional observations that explain CHL seen in clinical patients with abnormal TM, e.g., caused by otitis media, that have healed spontaneously after perforation or post-tympanoplasty, especially at high frequencies. In addition, our data demonstrate that changes in distortion product otoacoustic emissions (DPOAEs) result from altered ME transmission in both the forward and reverse direction by a reduction of the effective stimulus levels and less efficient transfer of DPs from the ME into the ear canal. This confirms that DPOAEs can be used to assess both the health of the cochlea and the middle ear.

Atlas-based segmentation of cochlear microstructures in cone beam CT.

To develop an automated segmentation approach for cochlear microstructures [scala tympani (ST), scala vestibuli (SV), modiolus (Mod), mid-modiolus (Mid-Mod), and round window membrane (RW)] in clinical cone beam computed tomography (CBCT) images of the temporal bone for use in surgical simulation software and for preoperative surgical evaluation. This approach was developed using the publicly available OpenEar (OE) Library that includes temporal bone specimens with spatially registered CBCT and 3D micro-slicing images. Five of these datasets were spatially aligned to our internal OSU atlas. An atlas of cochlear microstructures was created from one of the OE datasets. An affine registration of this atlas to the remaining OE CBCT images was used for automatically segmenting the cochlear microstructures. Quantitative metrics and visual review were used for validating the automatic segmentations. The average DICE metrics were 0.77 and 0.74 for the ST and SV, respectively. The average Hausdorff distance (AVG HD) was 0.11mm and 0.12mm for both scalae. The mean distance between the centroids for the round window was 0.32mm, and the mean AVG HD was 0.09mm. The mean distance and angular rotation between the mid-modiolar axes were 0.11mm and 9.8 degrees, respectively. Visually, the segmented structures were accurate and similar to that manually traced by an expert observer. An atlas-based approach using 3D micro-slicing data and affine spatial registration in the cochlear region was successful in segmenting cochlear microstructures of temporal bone anatomy for use in simulation software and potentially for pre-surgical planning and rehearsal.

Feasibility of Cochlea High-frequency Ultrasound and Microcomputed Tomography Registration for Cochlear Computer-assisted Surgery: A Testbed.

There remains no standard imaging method that allows computer-assisted surgery of the cochlea in real time. However, recent evidence suggests that high-frequency ultrasound (HFUS) could permit real-time visualization of cochlear architecture. Registration with an imaging modality that suffers neither attenuation nor conical deformation could reveal useful anatomical landmarks to surgeons. Our study aimed to address the feasibility of an automated three-dimensional (3D) HFUS/microCT registration, and to evaluate the identification of cochlear structures using 2D/3D HFUS and microCT. MicroCT, and 2D/3D 40 MHz US in B-mode were performed on ex vivo guinea pig cochlea. An automatic rigid registration algorithm was applied to segmented 3D images. This automatic registration was then compared to a reference method using manual annotated landmarks placed by two senior otologists. Inter- and intrarater reliabilities were evaluated using intraclass correlation coefficient (ICC) and the mean registration error was calculated. 3D HFUS/microCT automatic registration was successful. Excellent levels of concordance were achieved with regards intra-rater reliability for both raters with micro-CT and US images (ICC ranging from 0.98 to 1, p < 0.001) and with regards inter-rater reliability (ICC ranging from 0.99 to 1, p < 0.001). The mean HFUS/microCT automated RE for both observers was 0.17 ± 0.03 mm [0.10-0.25]. Identification of the basilar membrane, modiolus, scala tympani, and scala vestibuli was possible with 2D/3D HFUS and micro-CT. HFUS/microCT image registration is feasible. 2D/3D HFUS and microCT allow the visualization of cochlear structures. Many potential clinical applications are conceivable.

Radiological and Audiological Outcomes of the LISTENT LCI-20PI Cochlear Implant Device.

To study the surgical results, intracochlear position of the electrode array (EA) and auditory performance of the LISTENT LCI-20PI cochlear implant device, and daily use status at 3 years. A retrospective study. A single-tertiary referral center. Between January and December 2016, 20 patients underwent cochlear implantation using the LISTENT LCI-20PI (lateral wall EA). Cochlear implantation. Measurement of cochlear size, extent of posterior tympanotomy, and insertion depth. Scalar position of the EA evaluated by 3D reconstruction. Auditory outcomes 1 year after implantation and daily use status at 3 years. EAs were completely inserted in all cases with an insertion depth of 288 ± 36.8 degrees. One year later, the average sentence recognition score (SRS) was 90 ± 21.7%. EA scalar location was analyzed in 18 patients. Thirteen EAs (72.2%) were fully inserted into the scala tympani (ST) and 5 (27.8%) had shifted from the ST to the scala vestibuli (SV). There was no statistically significant difference in cochlear size, extent of posterior tympanotomy, or insertion depth between these two groups. EAs inserted by cochleostomy had a higher chance of scalar shift than those inserted via the round window (60% vs 15.4%, p = 0.099). SRS at 1 year with full ST insertion was significantly better than in those with scalar shift (99 ± 1.3% vs 83 ± 16.5%, p = 0.002). Three years after implantation, 92% of patients were daily users and 46% were telephone users. The LISTENT LCI-20PI provided accredited hearing rehabilitation with a short insertion depth. Full insertion into the ST was associated with better cochlear implantation outcomes.

A Micro-Computed Tomography Study of Round Window Anatomy and Implications for Atraumatic Cochlear Implant Insertion.

The goal of this study was to interrogate high-resolution three-dimensional reconstructions of round window anatomy to illustrate and characterize structural variability with implications for atraumatic cochlear implant insertion. Cochlear implants are increasingly used to improve sound detection in patients with substantial residual hearing. However, traumatic cochlear implant insertion through the round window involving upward deviation of the electrode into the spiral ligament, basilar membrane, and osseous spiral lamina, medial impaction on the modiolus, or interscalar excursion into the scala vestibuli are associated with lower rates of hearing preservation and poorer speech perception.Successful atraumatic insertion is dependent on an anatomical understanding of the middle and inner ear. The round window bony niche lacks distinct demonstrable anatomical landmarks for the position of the round window membrane, and there is limited guidance on the amount of bony overhang that can be safely drilled away. A greater understanding of the anatomical variation around the round window could enhance treatment efficacy. Fourteen human cadaver temporal bones were imaged using microcomputed tomography. Resulting scans were digitally reconstructed, segmented, and measured. Round window niche walls vary substantially in size and projection. Round window average short diameter measured 1.30 mm (range 1.07-1.44), and is limited by the crista fenestrae at the inferoanterior margin of the round window. Crista fenestrae size and morphology varied considerably. Reconstructions with solid and translucent panels are presented. Anatomical heterogeneity should be considered in cochlear implant selection, drilling, and choice of insertion vector.

HFUS Imaging of the Cochlea: A Feasibility Study for Anatomical Identification by Registration with MicroCT.

Cochlear implantation consists in electrically stimulating the auditory nerve by inserting an electrode array inside the cochlea, a bony structure of the inner ear. In the absence of any visual feedback, the insertion results in many cases of damages of the internal structures. This paper presents a feasibility study on intraoperative imaging and identification of cochlear structures with high-frequency ultrasound (HFUS). 6 ex-vivo guinea pig cochleae were subjected to both US and microcomputed tomography (µCT) we respectively referred as intraoperative and preoperative modalities. For each sample, registration based on simulating US from the scanner was performed to allow a precise matching between the visible structures. According to two otologists, the procedure led to a target registration error of 0.32mm ± 0.05. Thanks to referring to a better preoperative anatomical representation, we were able to intraoperatively identify the modiolus, both scalae vestibuli and tympani and deduce the location of the basilar membrane, all of which is of great interest for cochlear implantation. Our main objective is to extend this procedure to the human case and thus provide a new tool for inner ear surgery.