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Abstract Objectives This study aimed to qualitatively evaluate the variations in nerve bundles between patients with normal anatomy and those with inner‐ear anomalies. Methods Magnetic resonance imaging (MRI) scans of the temporal bones of candidates for cochlear implants (CIs) enrolled at a tertiary center were retrospectively reviewed from the clinical database. The 3.0‐Tesla MRI scans were analyzed using a three‐dimensional slicer to visualize the nerve bundles in the internal auditory canal. Results A total of 49 ears were analyzed. Twenty ears exhibited normal inner ear anatomy, whereas 29 ears had various inner‐ear malformations. The cochlear nerve (CN) was visible on all 20 scans with normal inner‐ear anatomy. In addition, the CN was visualized in 18 scans with inner ear malformations. Furthermore, the CN was identified in six of the eight scans with IP type I, whereas in two scans, the CN and vestibular nerve were unclear. Three scans with a common cavity showed only two nerve bundles. Conclusion The findings of this study show that the CN can be visualized in most inner‐ear anatomical types. Even in severely malformed inner ears, the common nerve bundle that represents the cochlear and vestibular nerves can be visualized. The MRI is highly recommended for CN assessment before CI surgery. Level of Evidence Level IV.

Objectives: This study aimed to qualitatively evaluate the variations in nerve bundles between patients with normal anatomy and those with inner‐ear anomalies. Methods: Magnetic resonance imaging (MRI) scans of the temporal bones of candidates for cochlear implants (CIs) enrolled at a tertiary center were retrospectively reviewed from the clinical database. The 3.0‐Tesla MRI scans were analyzed using a three‐dimensional slicer to visualize the nerve bundles in the internal auditory canal. Results: A total of 49 ears were analyzed. Twenty ears exhibited normal inner ear anatomy, whereas 29 ears had various inner‐ear malformations. The cochlear nerve (CN) was visible on all 20 scans with normal inner‐ear anatomy. In addition, the CN was visualized in 18 scans with inner ear malformations. Furthermore, the CN was identified in six of the eight scans with IP type I, whereas in two scans, the CN and vestibular nerve were unclear. Three scans with a common cavity showed only two nerve bundles. Conclusion: The findings of this study show that the CN can be visualized in most inner‐ear anatomical types. Even in severely malformed inner ears, the common nerve bundle that represents the cochlear and vestibular nerves can be visualized. The MRI is highly recommended for CN assessment before CI surgery. Level of Evidence: Level IV. [ABSTRACT FROM AUTHOR]

The optimal placement of a cochlear implant (CI) electrode inside the scala tympani compartment to create an effective electrode--neural interface is the base for a successful CI treatment. The characteristics of an effective electrode design include (a) electrode matching every possible variation in the inner ear size, shape, and anatomy, (b) electrically covering most of the neuronal elements, and (c) preserving intra-cochlear structures, even in non-hearing preservation surgeries. Flexible electrode arrays of various lengths are required to reach an angular insertion depth of 680° to which neuronal cell bodies are angularly distributed and to minimize the rate of electrode scalar deviation. At the time of writing this article, the current scientific evidence indicates that straight lateral wall electrode outperforms perimodiolar electrode by preventing electrode tip fold-over and scalar deviation. Most of the available literature on electrode insertion depth and hearing outcomes supports the practice of physically placing an electrode to cover both the basal and middle turns of the cochlea. This is only achievable with longer straight lateral wall electrodes as single-sized and preshaped perimodiolar electrodes have limitations in reaching beyond the basal turn of the cochlea and in offering consistent modiolar hugging placement in every cochlea. For malformed inner ear anatomies that lack a central modiolar trunk, the perimodiolar electrode is not an effective electrode choice. Most of the literature has failed to demonstrate superiority in hearing outcomes when comparing perimodiolar electrodes with straight lateral wall electrodes from single CI manufacturers. In summary, flexible and straight lateral wall electrode type is reported to be gentle to intra-cochlear structures and has the potential to electrically stimulate most of the neuronal elements, which are necessary in bringing full benefit of the CI device to recipients. [ABSTRACT FROM AUTHOR]

Estimating insertion depth, cochlear duct length (CDL), and other inner ear parameters is vital to optimizing cochlear implantation outcomes. Most current formulas use only the basal turn dimensions for CDL prediction. In this study, we investigated the importance of the second turn parameters in estimating CDL. Two experienced neuro-otologists blindly used segmentation software to measure (in mm) cochlear parameters, including basal turn diameter (A), basal turn width (B), second-turn diameter (A2), second-turn width (B2), CDL, first-turn length, and second-turn length (STL). These readings were taken from 33 computed tomography (CT) images of temporal bones from anatomically normal ears. We constructed regression models using A, B, A2, and B2 values fitted to CDL, two-turn length, and five-fold cross-validation to ensure model validity. CDL, A value, and STL were longer in males than in females. The mean B2/A2 ratio was 0.91 ± 0.06. Adding A2 and B2 values improved CDL prediction accuracy to 86.11%. Therefore, we propose a new formula for more accurate CDL estimation using A, B, A2, and B2 values. In conclusion, the findings of this study revealed a notable improvement in the prediction of two-turn length (2TL), and CDL by clinically appreciable margins upon adding A2 and B2 values to the prediction formulas. [ABSTRACT FROM AUTHOR]

Objective: To report a reliable method in obtaining optimal cochlear basal turn and cross‐section (c/s) of internal auditory canal (IAC) supporting Cochlear implantation (CI) procedure. Materials and Methods: Computer tomography (CT) and magnetic resonance image (MRI) scans of potential CI candidates from 2018 to 2022 from the tertiary center were considered for analysis. Slicer software was used in three‐dimensional (3D) segmentation of inner ear and for capturing the cochlear basal turn. Results: A total of 1932 head scans were made available for the analysis and out of which 1866 scans had normal anatomy (NA) inner ear. Incomplete partition (IP) type‐I was identified in 19 ears, IP type‐II in 27 ears, IP type‐III in 6 ears, cochlear hypoplasia (CH) type‐I in 6 ears, CH type‐II in 1 ear, CH type‐III in 3 ears, and CH type‐IV is 3 ears, and enlarged vestibular aqueduct syndrome in 1 ear. 3D segmented inner ear helped in successfully obtaining the cochlear basal turn and the c/s of IAC in all anatomical types. Time taken to capture the cochlear basal turn with the help of 3D segmented inner ear was <1 min. Within the NA category, five cases showed scalar ossification, and its extent was identified in the cochlear basal turn. Conclusion: The identification and the extent of ossification in the scala tympani, shape of the basal turn, and the cochlear size measurement in cochlear basal turn has high clinical relevance as this helps in surgical planning and in choosing appropriate electrode length. Level of evidence: Level 2 to the best of our understanding. [ABSTRACT FROM AUTHOR]

Purpose: A narrow bony internal auditory canal (IAC) may be associated with a hypoplastic cochlear nerve and poorer hearing performances after cochlear implantation. However, definitions for a narrow IAC vary widely and commonly, qualitative grading or two-dimensional measures are used to characterize a narrow IAC. We aimed to refine the definition of a narrow IAC by determining IAC volume in both control patients and patients with inner ear malformations (IEMs). Methods: In this multicentric study, we included high-resolution CT (HRCT) scans of 128 temporal bones (85 with IEMs: cochlear aplasia, n = 11; common cavity, n = 2; cochlear hypoplasia type, n = 19; incomplete partition type I/III, n = 8/8; Mondini malformation, n = 16; enlarged vestibular aqueduct syndrome, n = 19; 45 controls). The IAC diameter was measured in the axial plane and the IAC volume was measured by semi-automatic segmentation and three-dimensional reconstruction. Results: In controls, the mean IAC diameter was 5.5 mm (SD 1.1 mm) and the mean IAC volume was 175.3 mm3 (SD 52.6 mm3). Statistically significant differences in IAC volumes were found in cochlear aplasia (68.3 mm3, p < 0.0001), IPI (107.4 mm3, p = 0.04), and IPIII (277.5 mm3, p = 0.0004 mm3). Inter-rater reliability was higher in IAC volume than in IAC diameter (intraclass correlation coefficient 0.92 vs. 0.77). Conclusions: Volumetric measurement of IAC in cases of IEMs reduces measurement variability and may add to classifying IEMs. Since a hypoplastic IAC can be associated with a hypoplastic cochlear nerve and sensorineural hearing loss, radiologic assessment of the IAC is crucial in patients with severe sensorineural hearing loss undergoing cochlear implantation. [ABSTRACT FROM AUTHOR]

The mathematical equations to estimate cochlear duct length (CDL) using cochlear parameters such as basal turn diameter (A-value) and width (B-value) are currently applied for cochleae with two and a half turns of normal development. Most of the inner ear malformation (IEM) types have either less than two and a half cochlear turns or have a cystic apex, making the current available CDL equations unsuitable for cochleae with abnormal anatomies. Therefore, this study aimed to estimate the basal turn length (BTL) from the cochlear parameters of different anatomical types, including normal anatomy; enlarged vestibular aqueduct; incomplete partition types I, II, and III; and cochlear hypoplasia. The lateral wall was manually tracked for 360° of the angular depth, along with the A and B values in the oblique coronal view for all anatomical types. A strong positive linear correlation was observed between BTL and the A- (r2 = 0.74) and B-values (r2 = 0.84). The multiple linear regression model to predict the BTL from the A-and B-values resulted in the following equation (estimated BTL = [A × 1.04] + [B × 1.89] − 0.92). The manually measured and estimated BTL differed by 1.12%. The proposed equation could be beneficial in adequately selecting an electrode that covers the basal turn in deformed cochleae. [ABSTRACT FROM AUTHOR]

Objective: We hypothesize that visualizing inner‐ear systematically in both cochlear view (oblique coronal plane) and in mid‐modiolar section (axial plane) and following three sequential steps simplifies, identification of inner‐ear malformation types. Methods: Pre‐operative computer‐tomography (CT) scans of temporal bones of 112 ears with various inner ear malformation (IEM) types were taken for analysis. Images were analyzed using DICOM viewers, 3D slicer, and OTOPLAN®. The inner‐ear was captured in the oblique‐coronal plane for the measurement of length and width of cochlear basal turn which is also called as A‐, and B‐values respectively (Step 1). In the same plane, the angular‐turns of lateral‐wall (LW) of cochlear basal turn were measured (Step 2). As Step 3, the mid‐modiolar section of inner ear was captured in the axial plane by following the A‐value and perpendicular to cochlear view. From the mid‐modiolar section, the outer‐contour of inner ear was captured manually by following contrasting gray area between fluid filled and bony promontory and was compared to known resembling objects to identify IEM types (Step 3). Results: Following reference values have emerged from our analysis: A‐, and B‐values (Step 1) on average are >8 mm and >5.5 mm respectively, in normal cochleae (NA), enlarged vestibular aqueduct syndrome (EVAS), incomplete partition (IP) type‐I and ‐II, whereas it is <8 mm and <5.5 mm respectively, in IP type‐III and cochlear hypoplasia (CH). Angular‐turn of LW is consistently observed in cochlear basal turn (Step 2), is 540° in NA and EVAS, 450° in IP‐II, and 360° in IP types I & III. In subjects with CH type, angular‐turn of LW is either 360° or 450° or 540°. In true mid‐modiolar section, outer‐contour of inner‐ear (Step‐3), other than in CH and cystic inner‐ear malformations, resembles recognizable shapes of known objects. Absence of EVA is an additional characteristic that confirms diagnosis of CH when the A‐, B‐values, and angular‐turn of LW can be similar to other anatomical types. Drawing a straight line along posterior edge of internal auditory canal (IAC) in axial view can differentiate a true common cavity (CC) from cochlear aplasia‐vestibular cavity (VC). Conclusion: Three‐step process proposed in this study captures inner‐ear in cochlear view as well in mid‐modiolar sections visualizing key features of inner‐ear in identification of IEM types. Level of Evidence: Level 1. [ABSTRACT FROM AUTHOR]

Object: To investigate the long-term development of auditory and speech in patients with common cavity deformity (CCD) after cochlear implantation (CI) and its relationship to imaging characteristics. Methods: Twenty-three CCD patients and 59 age- and sex-matched CI children with normal inner ear structure were recruited. The auditory and speech development of these two groups were evaluated at 0, 1, 3, 6, 12, and 18 months after CI activation using four parent reports questionnaires [Categories of Auditory Performance (CAP), Speech Intelligibility Rating (SIR), Meaningful Auditory Integration Scale/Infant-Toddler Meaningful Auditory Integration Scale (MAIS/ITMAIS), and Meaningful Use of Speech Scale (MUSS)]. Computed tomography-based 3-dimensional reconstruction of the surgical side of 18 CCD children was performed, the volume and surface area were calculated. Correlation analysis was performed on the imaging performance and post-operative outcomes. Results: The percentages of MAIS/IT-MAIS scores and CAP scores at different evaluation time points are significantly different (p < 0.05). When comparing SIR results across time points, significant growth was observed in most of the comparisons. In addition, significant differences (p < 0.05) are observed among the percentages of MUSS scores at different time points except the comparison between 0 and 1 month after CI activation. Patients in the CCD group had poorer auditory and speech performances at different stages after CI compared with those in the control group. According to the reconstruction of CCD patients, the volume ranged from 12.21 to 291.96 mm3; the surface area ranged from 27.81 to 284.7 mm2. When the lumen surface area was <190.45 mm2 or the volume was <157.91 mm3, the survival time for CCD children to achieve a CAP score of 4 after CI was significantly shorter. Conclusion: Cochlear implantation are less effective in CCD patients than in patients with normal inner ear structures, but they can still achieve significant improvement post-operatively. The morphology and size of the inner ear vary in CCD patients, which reflects the degree of inner ear development influences the outcome after CI surgery. [ABSTRACT FROM AUTHOR]

Identification of the inner ear malformation types from radiographs is a complex process. We hypothesize that each inner ear anatomical type has a uniqueness in its appearance in radiographs. The outer contour of the inner ear was captured from the mid-modiolar section, perpendicular to the oblique-coronal plane, from which the A-value was determined from CT scans with different inner ear anatomical types. The mean A-value of normal anatomy (NA) and enlarged vestibular aqueduct syndrome (EVAS) anatomical types was greater than for Incomplete Partition (IP) type I, II, III and cochlear hypoplasia. The outer contour of the cochlear portion within the mid-modiolar section of NA and EVAS resembles the side view of Aladdin's lamp; IP type I resembles the side-view of the Sphinx pyramid and type II a Pomeranian dog's face. The steep spiraling cochlear turns of IP type III resemble an Auger screw tip. Drawing a line parallel to the posterior margin of internal auditory canal (IAC) in axial-view, bisecting the cavity into cochlear and vestibular portions, identifies common-cavity; whereas a cavity that falls under the straight-line leaving no cochlear portion identifies cochlear aplasia. An atlas of the outer contour of seventy-eight inner ears was created for the identification of the inner malformation types precisely. [ABSTRACT FROM AUTHOR]

Optimal matching of an electrode array to the cochlear anatomy plays a key role in bringing the best benefit of CI technology to the users. Even within the category of normal anatomy cochlea, the size variation is huge justifying MED-EL's FLEX electrode array to be available in five different lengths. Within the malformed inner-ear category the anatomical variation is huge, convincing MED-EL to custom-design the electrode array as per the request from the operating surgeons. Thanks to G. Bredberg, M. Beltrame, L. Sennaroglu, J. Gavilan, S. Plontke, T. Lenarz, J. M€uller, and few others for their valuable suggestions on unique electrode designs satisfying various needs. Translational research efforts at MED-EL in cooperation with CI surgeons from across the world led to the implantation of a variety of electrode array designs in patients with special cochlear needs. [ABSTRACT FROM AUTHOR]

Fibrous tissue growth and loss of residual hearing after cochlear implantation can be reduced by application of the glucocorticoid dexamethasone-21-phosphate-disodium-salt (DEX). To date, sustained delivery of this agent to the cochlea using a number of pharmaceutical technologies has not been entirely successful. In this study we examine a novel way of continuous local drug application into the inner ear using a refillable hydrogel functionalized silicone reservoir. A PEG-based hydrogel made of reactive NCO-sP(EO-stat-PO) prepolymers was evaluated as a drug conveying and delivery system in vitro and in vivo. Encapsulating the free form hydrogel into a silicone tube with a small opening for the drug diffusion resulted in delayed drug release but unaffected diffusion of DEX through the gel compared to the free form hydrogel. Additionally, controlled DEX release over several weeks could be demonstrated using the hydrogel filled reservoir. Using a guinea-pig cochlear trauma model the reservoir delivery of DEX significantly protected residual hearing and reduced fibrosis. As well as being used as a device in its own right or in combination with cochlear implants, the hydrogel-filled reservoir represents a new drug delivery system that feasibly could be replenished with therapeutic agents to provide sustained treatment of the inner ear. [ABSTRACT FROM AUTHOR]

Objective: To understand the anatomical and dimensional variations of the human inner ear using 3-dimensional (3D) segmentation within the Middle East population. Design: Retrospective study. Setting: King Abdullah Ear Specialist Center (KAESC) Riyadh, Saudi Arabia. Participant: Forty computed tomography (CT) images of patients with sensorineural hearing loss who underwent cochlear implant (CI) were taken for analysis. Main outcome Measures: Three-dimensional images showing the anatomical variations of the inner ear including various pathological conditions, cochlear parameters including basal turn diameter ("A" value), "B" value which is perpendicular to "A" value, cochlear height, length, and width of the internal auditory canal (IAC), intercochlear spacing, and electrode angular insertion depth (AID). Results: Out of 40 CT image data sets, 12 had normal inner-ear anatomy (NA), 4 with enlarged vestibular aqueduct syndrome (EVAS), 8 with only 2 turns of the cochlea (2TL), 7 with incomplete partition (IP) type II, 5 with cochlear hypoplasia, 1 with common cavity, and 3 with abnormal IAC. Taking the NA, EVAS, 2TL, and the IP type II cases altogether, age of the patient had no correlation with the "A" value; however, the "A" value had a linear correlation with the "B" value. The age of the patient had an increasing logarithmic correlation with the IAC length and the intercochlear spacing. The "A" value did not have any meaningful correlation with the cochlear height. Three data sets showed asymmetric inner-ear malformation types on either side of the ears. All these 40 cases were implanted with various CI electrode array variants and the corresponding postoperative plain film X-ray images showing the electrode AID are given separately in figures. Conclusions: Three-dimensional segmentation of the inner ear from the temporal bone CT is a valuable clinical and training tool for surgeons and radiologists especially in difficult cases which will certainly help to understand the overall anatomical and dimensional variations. [ABSTRACT FROM AUTHOR]