Normal Cochlea Research Articles

Morphology of the human inner ear and vestibulocochlear nerve assessed using 7 T MRI

Abstract Objective To optimize high-resolution 7 T MRI of the cochlea and measure normal cochlea and the cochlear nerve morphometry in vivo. Materials and methods Eight volunteers with normal hearing were scanned at 7 T using an optimized protocol. Two neuroradiologists independently scored image quality. The basal turn lumen diameter (BTLD), height, width, length and volume of the cochlear, long (LD) and short (SD) diameter the calculated cross-sectional area (CSA) of the cochlear nerve were measured. Intra and inter-observer reliability was assessed using intraclass correlation (ICC). Results 3D T2W DRIVE combined with dielectric pads, allowed acquisition of high-resolution images showing detailed structures, such as the crista ampullaris in the semicircular canals. The overall grading scores from neuroradiologists were excellent. In the left ear, averaging over all subjects gave BTLD of 2.6 ± 0.05 mm, height of 4.9 ± 0.1 mm, width of 4.4 ± 0.2 mm, length of 36.5 ± 0.4 mm, volume of 0.16 ± 0.02 ml, LD of 1.31 ± 0.1 mm, SD of 1.06 ± 0.1 mm, and CSA of 1.1 ± 0.1 mm2. The right ear gave BTLD of 2.6 ± 0.04 mm, height of 4.9 ± 0.1 mm, width of 4.4 ± 0.3 mm, length of 35.5 ± 0.4 mm, volume of 0.16 ± 0.02 ml, LD of 1.29 ± 0.1 mm, SD of 1.07 ± 0.1 mm, and CSA of 1.10 ± 0.2 mm2. No statistically significant difference was found between the sides of the head (p-value > 0.05). The intra-observer reliability was high (0.77–0.94), while the inter-observer reliability varied from moderate to high (0.55–0.81). Conclusion 7 T MRI can provide excellent visualization of the internal structure of the cochlear and of the vestibulocochlear nerve in vivo.

Morphometric Measurements of the Incomplete Partition Type II (IP-II) Cochlea and Implications on Cochlear Implantation.

The objective of this study is to obtain comprehensive morphometric measurements of the incomplete partition type II (IP-II) cochlea to provide a better understanding of intracochlear anatomy and important considerations for electrode selection and insertion. IP-II is the most common bony inner ear malformation that often requires cochlear implantation. Currently, there is significant controversy on electrode selection due to a lack of research that can provide reliable, high-resolution measurements. Three-dimensional reconstructions of the cochlea were made from hematoxylin and eosin-stained slides from 11 archival human temporal bones from 8 adult IP-II patients (one paired) and 2 fetuses. Detailed measurements of the angular and linear length of the spiral ganglion neurons and cochlear duct at the modiolar and lateral wall of the scala tympani as well as cross-sectional areas and vertical height measurements of the scala tympani at 90-degree intervals were measured. The spiral ganglia neurons terminated at 540.5 ± 45.4 degrees, which corresponded to the beginning of the interscalar septal defect. The corresponding Rosenthal's canal length was 12.75 ± 0.82 mm, and the lateral wall length was 23.95 ± 1.04. The average cochlear duct length was 32.44 mm ± 1.58 mm, corresponding to an average angular distance of 951.6 ± 80 degrees. The modiolar height demonstrated less variation within the scala tympani but was significantly smaller at 0 and 90 degrees compared with the normal cochlea. The lateral wall height was also significantly smaller at 0, 180, and 540 degrees. There was a drastic decrease in lateral wall height at 540 degrees to 0.4 mm, which is smaller than the apical dimension of many electrodes. This is the first study to provide detailed morphometric measurements of the IP-II cochlea including spiral ganglion neuron length and scala tympani height. These measurements directly relate to electrode selection for cochlear implantation.

Hypoxia and Normoxia Preconditioned Olfactory Stem Cells Against Noise-Induced Hearing Loss.

Noise-induced hearing loss is one of the leading causes of permanent hearing loss in the adult population. In this experimental study, the authors aimed to investigate the effectiveness of hypoxia and normoxia preconditioned olfactory stem cells against noise trauma. Twenty-seven female guinea pigs were enrolled. Two guinea pigs were sacrificed for harvesting olfactory tissue and 1 for examining the architecture of the normal cochlea. The remaining 24 guinea pigs were exposed to noise trauma for 1 day and then randomly divided into 3 groups: intracochlear injection of (i) normoxic olfactory stem cells, (ii) hypoxic olfactory stem cells, and (iii) physiological serum. Auditory brainstem response (ABR) measurement was performed before and 2 weeks after noise trauma and weekly for 3 weeks following intracochlear injection. Both click and 16kHz tone-burst stimuli were used for detection of ABR. No significant difference was noted between the groups before and 2 weeks after noise trauma. ABR thresholds detected after intracochlear injections were significantly higher in the control group compared with stem cell groups. However, no significant difference was detected between the stem cell groups. Fluourescence microscopy revealed better engraftment for hypoxic stem cells. Light and electron microscopy examinations were consistent with predominant degenerative findings in the control group, whereas normoxic group had more similar findings with normal cochlea compared with hypoxic group. Olfactory stem cells were demonstrated to have the potential to have beneficial effects on noise trauma.

How differ eCAP types in cochlear implants users with and without inner ear malformations: amplitude growth function, spread of excitation, refractory recovery function.

Inner ear malformations (IEMs) may result in differences in outcomes of cochlear implant user. These differences could be observed in both behavioral and objective tests. eCAP is the most common used objective test in cochlear implants and have different presence rate in cochlear implant users with and without IEMs. This study aims to evaluate eCAP results from CI user with and without IEMs through different recoding methods; amplitude growth function, spreads of excitation and refractory recovery. There were 42 CI users (20 IEM&22 normal) above five-years old and with at least one year experience. Three different eCAP measurement was conducted at several intracochlear electrodes. Presence rate, threshold levels and amplitude were compared between groups. For Amplitude growth function measurement, when the percentage of detected eCAP thresholds was analyzed between groups, there was a significant difference only for basal electrode and no significant difference for apical and middle electrodes. Similarly, the presence rate of RecF-eCAP for both groups were in a downward trend from apical to basal. However, there was no significant difference in AGF-eCAP and RecF-eCAP amplitudes between groups for the cochlea's apical, middle and basal region. Although the presence rate of SOE-eCAP was lower for IEM group, there was no significant difference in ECAP amplitudes for all maskers. It could be inferred that even though the observable eCAP rate differed between these two groups when the observable eCAP was recorded, the IEM group produced eCAP with similar amplitudes to normal cochlea group.

Cochlear Implantation in Inner Ear Malformations

Introduction: Cochlear Implantation (CI) has proven to be an effective treatment for severe bilateral Sensorineural Hearing Loss (SNHL). Inner ear malformation is a rare anomaly and occurs in approximately 20% of cases with congenital SNHL. There are particular challenges in the implantation of malformed cochleae, such as in cases of facial nerve anomalies, Cerebrospinal Fluid (CSF) leaks or facial stimulation, and the outcomes may differ depending on the severity of the malformation. The aim of this study was to assess the impact of Inner Ear Malformations (IEMs) on surgical complications and outcomes of cochlear implantation. Methods: Between 2018 and 2022, 9 patients with inner ear malformations were implanted in our department and completed at least 1 year of follow-up. The age range was between 2 years and 4 months and 5 years (average, 3.36 yr). Auditory performance, receptive and expressive language skills, and production and use of speech were evaluated preoperatively and at least 1 year after implantation. Results: In the study group, the most common malformation was an isolated Enlarged Vestibular Aqueduct (EVA) (55,5%). Overall, the patients with IEMs showed significant improvement in auditory-verbal skills. In general, the patients who had normal cochleae scored significantly better compared to patients with IEMs. Conclusion: Based on these findings, cochlear implantation is surgically feasible in patients with common cavity, IP types I and II, and EVA. The surgeon should be ready to make modifications in the surgical approach because of the abnormal course of the facial nerve and be ready to produce special precautions to cerebrospinal fluid gusher. Patients with EVA were the best performers in terms of auditory-verbal skills.

Otological Planning Software-OTOPLAN: A Narrative Literature Review.

The cochlear implant (CI) is a widely accepted option in patients with severe to profound hearing loss receiving limited benefit from traditional hearing aids. CI surgery uses a default setting for frequency allocation aiming to reproduce tonotopicity, thus mimicking the normal cochlea. One emerging instrument that may substantially help the surgeon before, during, and after the surgery is a surgical planning software product developed in collaboration by CASCINATION AG (Bern, Switzerland) and MED-EL (Innsbruck Austria). The aim of this narrative review is to present an overview of the main features of this otological planning software, called OTOPLAN®. The literature was searched on the PubMed and Web of Science databases. The search terms used were "OTOPLAN", "cochlear planning software" "three-dimensional imaging", "3D segmentation", and "cochlear implant" combined into different queries. This strategy yielded 52 publications, and a total of 31 studies were included. The review of the literature revealed that OTOPLAN is a useful tool for otologists and audiologists as it improves preoperative surgical planning both in adults and in children, guides the intraoperative procedure and allows postoperative evaluation of the CI.

Determining optimal cochlear implant electrode array with OTOPLAN

Background To achieve better speech performance following cochlear implantation (CI), measuring the patient’s cochlear duct length (CDL) and determining the appropriate length of the CI array are important. Objective To investigate the CDL in CI patients after using the OTOPLAN software preoperatively and compare the results of angular insertion depth (AID) estimation by OTOPLAN and postoperative radiography. Materials and Methods The study included 105 Japanese CI patients with normal cochleae. We measured the CDL using OTOPLAN and the position of the tip channel of the electrode for each selected electrode array, and estimated the AID using the software. Results The mean CDL was 35.1 ± 1.6 mm. Preoperatively, the mean estimated AID was 580.3 ± 57.8°. Postoperative radiography revealed a mean AID of 583.0 ± 56.7°, demonstrating a strong linear correlation between the two measurements (R2 = 0.635). Conclusion and Significance Our findings revealed that CDL varies widely, which is consistent with previous studies. To achieve better speech perception, surgeons should select the appropriate length of CI electrode array based on the individual’s CDL. Preoperative measurement of each CDL by OTOPLAN, which is clinically feasible and comparable to postoperative evaluation, can be used to ensure selection of the appropriate electrode array length.

Incomplete Partition Type II Cochlear Malformations: Delineating the Three-Dimensional Structure from Digitized Human Histopathological Specimens.

There are clinically relevant differences in scalae anatomy and spiral ganglion neuron (SGN) quantity between incomplete partition type II (IP-II) and normal cochleae. IP-II is a commonly implanted cochlear malformation. Detailed knowledge of intracochlear three-dimensional (3D) morphology may assist with cochlear implant (CI) electrode selection/design and enable optimization of audiologic programming based on SGN maps. IP-II (n = 11) human temporal bone histological specimens were identified from the National Institute on Deafness and Other Communication Disorders National Temporal Bone Registry and digitized. The cochlear duct, scalae, and surgically relevant anatomy were reconstructed in 3D. A machine learning algorithm was applied to map the location and number of SGNs. 3D scalae morphology of the basal turn was normal. Scala tympani (ST) remained isolated for 540 degrees before fusing with scala vestibuli. Mean ST volume reduced below 1 mm 2 after the first 340 degrees. Scala media was a distinct endolymphatic compartment throughout; mean ± standard deviation cochlear duct length was 28 ± 3 mm. SGNs were reduced compared with age-matched norms (mean, 48%; range, 5-90%). In some cases, SGNs failed to ascend Rosenthal's canal, remaining in an abnormal basalward modiolar location. Two forms of IP-II were seen: type A and type B. A majority (98-100%) of SGNs were located in the basal modiolus in type B IP-II, compared with 76 to 85% in type A. Hallmark features of IP-II cochleae include the following: 1) fusion of the ST and scala vestibuli at a mean of 540 degrees, 2) highly variable and overall reduced SGN quantity compared with normative controls, and 3) abnormal SGN distribution with cell bodies failing to ascend Rosenthal's canal.

Characteristics of responsiveness of cochlear nerve to electrical stimulation in patients with cochlear nerve deficiency

Objectives: This study aimed to evaluate the responsiveness of cochlear nerve to electrical stimulation in patients with cochlear nerve deficiency(CND), to compare their results with those measured in implanted children with normal-sized cochlear nerves, and to investigate the characteristics of the cochlear nerve injury of children with CND. Methods: Participants were children who underwent cochlear implantation at Shandong Provincial ENT Hospital from January 2012 to January 2020, including CND group and control group. The CND group included 51 subjects (male:20; female: 31) who were diagnosed with CND and had normal cochlea. For the CND group, four children had been bilaterally implanted, the mean implantation age was (2.7±1.5) years old. The control group included 21 subjects (male:10; femal:11) who had normal-sized cochlear nerve and normal cochlea. For the control group, all children had been unilaterally implanted except one, and the mean implantation age was (3.0±1.9)years old. Three subjects in the CND group used CI422 electrode arrays, and all the other subjects used CI24RECA/CI512 electrode arrays. The electrically evoked compound action potentials (ECAP) had been tried to record for each electrode using Custom Sound EP software (v. 4.3, Cochlear Ltd.) at least six months post first activation. Furthermore, ECAP amplitude growth functions (AGF) were measured at multiple electrode locations across the electrode array. Generalized linear mixed effect models with the subject group and electrode location as the fixed effects and subjects as the random effect were used to compare results of ECAP measurements. Results: In the control group, ECAP could been recorded at all electrodes (100%), but it could only be recorded in 71% (859/1 210) electrodes in the CND group. Additionally, the percentage of electrodes with measurable ECAP decreased from electrode 1 to electrode 22 in the CND group. Compared to the control group, the ECAP thresholds significantly increased, the ECAP amplitudes and AGF slopes significantly decreased, and the ECAP latency significantly increased in the CND group (P<0.01). GLMM showed that the stimulating site had a significant effect on the ECAP threshold, maximum amplitude, and AGF slope (P<0.01), but had no significant effect on the ECAP latency (P>0.05) in the CND group. However, the stimulating site had no significant effects on the ECAP measurements in the control group. Furthermore, the functional status of cochlear nerve varied greatly among CND group. From electrode 1 to electrode 22, the ECAP thresholds gradually increased, the ECAP maximum amplitudes and AGF slopes gradually decreased in the CND group. Conclusion: Compared with patients with normal-sized cochlear nerve, not only the number of residual spinal ganglion neurons reduce,but also the function of spinal ganglion neurons damages in CND patients. The degree of cochlea nerve deterioration varies greatly among CND patients. Generally, the deterioration of cochlear nerve tends to increase from the basal to the apical site of the cochlea.

Tonotopic fitting of the sound processor cochlear implant in normal cochlea anatomy

Introduction. Cochlear implantation is very effective due to the known tonotopic organization of the cochlea. These data are used in the distribution of signals along the channels of the cochlear implant electrode. The more accurate and natural the stimulation of the auditory nerve fibers, the better the perception of speech, sounds and speech intelligibility.The aim of the study was to compare the clinical and anatomical settings of the cochlear implant processor.Materials and methods. The study included 63 patients aged 2 to 60 years using cochlear implantation system, implants with a standard long electrode array (31.5 mm). All participants underwent computed tomography (CT) of the temporal bones with a step of 0.6 mm or less. CT data were processed using Otoplan and Sliser 3D software. The geometric dimensions of the cochlea, the length of the cochlear canal, the angular position and tonotopic frequency of each electrode were calculated, and a 3D reconstruction of the cochlea and electrode was built.Results. The correction of the frequency filters of the electrodes and the anatomical adjustment of the processor were performed according to the data obtained in the Otoplan program. A comparison was made between the clinical and anatomical setting. After the redistribution of frequency filters, patients noted a more natural sound, improved speech intelligibility. Thus, with anatomical adjustment, an exact correspondence is achieved between the central frequency of each electrode channel and the tonotopic frequency of the cochlear zone, individually determined by computed tomography.Conclusions. A new tool has appeared that allows you to significantly improve the quality and provide an individual approach to setting up processors after cochlear implantation.

Cochlear implantation programming characteristics and outcomes of cochlear nerve deficiency.

Due to the specificity of cochlear implantation (CI) programming parameters and outcomes in cochlear nerve deficiency (CND) patients, this study aimed to investigate the correlation between programming parameters and outcomes and further compare the difference between normal and CND groups. Ninety (95 ears) CND patients (normal cochlea, 39; malformed cochlea, 56) and seventy-nine (81 ears) normal cochlea patients who underwent CI surgery with either Med-El or Cochlear devices were included. The programming parameters and outcomes evaluated by the questionnaires were collected and compared among the normal CND, malformed CND, and normal groups in the two device groups, and their correlation was analyzed. In the CND group, a reduced stimulation rate, higher pulse width, and triphasic pulse were needed in some cases. The stimulus levels of the CND group were significantly higher than that of the normal group (p < 0.05), but the outcomes of the CND group were significantly worse than that of the normal group (p < 0.05), and the stimulus level was significantly correlated with the outcomes (p < 0.05). However, there was no difference between normal and malformed CND groups. The non-auditory response was observed in the CND group, especially the ones with malformations. The CI programming parameters of some CND patients need to be adjusted, and a slower stimulation rate and higher pulse width are required sometimes. CND patients need a higher stimulus level than normal patients but their outcomes are poorer. Non-auditory response should be noticed in CND patients during programming.

The Cochlear Size Variations in Incomplete Partitions with Multiplanar Images on Pediatric Temporal Bone CT.

The purpose of the study was to evaluate cochlea dimensions by the multiplanar reconstruction of high-resolution computed tomography that could be useful in diagnosing incomplete partition (IP) malformations. This study included 32 patients with 64 side cochleae diagnosed with IP defect and 38 cochleae as the control without any defect. Basal turn length (BL), cochlear height (CH), Mid-apical length (MAL), Mid-apical height, Cochlear length (A), and Cochlear width (B) were measured on reformat images. Twenty cochleae of these patients have been diagnosed with IP type I, 34 with IP type II, and 10 with IP type III. The MAL values are shorter than the control group in IP types I and III (p<0.001, p<0.001). BL values are shorter in IP type III cases (p<0.001). In IP II cases, BL and MAL values overlapped with the control group. CH did not differ significantly from the control group in any IP type. A and B values were significantly lower than the control group for IP I and III (p<0.01). There is a positive correlation between A and B values for all IP types (p<0.01). Quantitative data about differences in the size and shape of the cochlea in IP cases would help differentiate them from the normal cochlea. Since A and B values showed a positive correlation, it is suggested that A and B values can be used to estimate CDL for IP types.

Surgical tactic of cochlear implantation in patients with intraoperative CSF leakage

Cochlear implantation (CI) is currently the recognized and most promising method of rehabilitation of patients suffering from profound hearing loss and deafness. During the surgical stage of CI, one of the most unpleasant intraoperative features is CSF leakage from the cochlea opening. Most often it occurs in patients with malformations of the inner ear, with temporal bone fractures and with cochlear otosclerosis. The difficulty of choosing the tactics of surgical intervention in these patients is caused by the large variability of the anatomical structures of the inner ear. In the period from 2017 to 2021, 1954 patients underwent CI, of which 83 were patients with cochlea malformations (65 intraoperative CSF leakages), 14 with the temporal bones fractures (2 intraoperative CSF leakage), 12 with cochlear otosclerosis (1 CSF leakage), while 3 spontaneous intraoperative CSF leakages were noted in patients with normal cochlea anatomy and hyperpnumotized temporal bone pyramid and enlarged vestibular aqueduct. The highest risk of intraoperative CSF leakage was observed in patients with inner ear malformations (common cavity - 10, incomplete partition type III - 15) and anomalies of the internal auditory canal - 5 (dilated IAC - more than 8.5 mm in diameter). Moderate risk of intraoperative CSF leakage was typical for patients with incomplete partition type I (15 patients) and type II (25 patients).

Analysis of SLC26A4, FOXI1, and KCNJ10 Gene Variants in Patients with Incomplete Partition of the Cochlea and Enlarged Vestibular Aqueduct (EVA) Anomalies

Pathogenic variants in the SLC26A4, FOXI1, and KCNJ10 genes are associated with hearing loss (HL) and specific inner ear abnormalities (DFNB4). In the present study, phenotype analyses, including clinical data collection, computed tomography (CT), and audiometric examination, were performed on deaf individuals from the Sakha Republic of Russia (Eastern Siberia). In cases with cochleovestibular malformations, molecular genetic analysis of the coding regions of the SLC26A4, FOXI1, and KCNJ10 genes associated with DFNB4 was completed. In six of the 165 patients (3.6%), CT scans revealed an incomplete partition of the cochlea (IP-1 and IP-2), in isolation or combined with an enlarged vestibular aqueduct (EVA) anomaly. Sequencing of the SLC26A4, FOXI1, and KCNJ10 genes was performed in these six patients. In the SLC26A4 gene, we identified four variants, namely c.85G>C p.(Glu29Gln), c.757A>G p.(Ile253Val), c.2027T>A p.(Leu676Gln), and c.2089+1G>A (IVS18+1G>A), which are known as pathogenic, as well as c.441G>A p.(Met147Ile), reported previously as a variant with uncertain significance. Using the AlphaFold algorithm, we found in silico evidence of the pathogenicity of this variant. We did not find any causative variants in the FOXI1 and KCNJ10 genes, nor did we find any evidence of digenic inheritance associated with double heterozygosity for these genes with monoallelic SLC26A4 variants. The contribution of biallelic SLC26A4 variants in patients with IP-1, IP-2, IP-2+EVA, and isolated EVA was 66.7% (DFNB4 in three patients, Pendred syndrome in one patient). Seventy-five percent of SLC26A4-biallelic patients had severe or profound HL. The morphology of the inner ear anomalies demonstrated that, among SLC26A4-biallelic patients, all types of incomplete partition of the cochlea are possible, from IP-1 and IP-2, to a normal cochlea. However, the dominant type of anomaly was IP-2+EVA (50.0%). This finding is very important for cochlear implantation, since the IP-2 anomaly does not have an increased risk of “gushers” and recurrent meningitis.

The value of threshold of neural response telemetry on the prediction of behavioral audiometry threshold after cochlear implantation patients

Objective:To explore the feasibility of using the threshold of neural response telemetry（NRT） to guide postoperative machine adjustment by analyzing the regularity and correlation between the threshold of subjective behavior test and NRT in cochlear implant patients with normal cochlear morphology and inner ear malformation. Methods:Thirty cochlear implant patients with normal cochlear morphology and 12 cochlear implant patients with inner ear malformation were selected for NRT test and subjective behavior test, respectively. Electrode 1 representing high frequency, electrode 11 representing medium frequency and electrode 22 representing low frequency were selected to analyze the correlation between NRT threshold and T value and C value. Results:The mean NRT threshold values of the cochlear normal group and the inner ear malformation group were both greater than T value, close to and slightly smaller than C value. The T value, C value and NRT threshold of the inner ear malformation group were slightly higher than those of the cochlear normal group. The NRT thresholds of high, middle and low frequency bands were significantly correlated with C and T values in the normal cochlear group and the inner ear malformation group. Compared with the normal cochlear group, the regression coefficients B of NRT threshold and T value in the high, medium and low frequency groups were 20.90%, 3.02%, 9.68%, and the K coefficients were 13.01%, 3.92%, 5.28%. The regression coefficients B of NRT threshold and C value of the two groups were 15.74%, 2.51%, 0.53%, and K were 14.44%, 0.24%, 4.09%, respectively. It can be seen that the correlation between NRT threshold and T value and C value of the two groups was significantly different in the high frequency band, but similar in the low and middle frequency band. Conclusion:The NRT threshold is significantly correlated with the threshold of subjective behavior test. The linear regression equation obtained can be used to guide the cochlear implant tuning machine, especially for the high frequency band T and C values of patients with inner ear malformation implantation. Different regression equations should be used to estimate the T and C values of patients with normal cochlea, so as to obtain more accurate T and C values.

A novel three-step process for the identification of inner ear malformation types.

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. 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). 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). 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 1.

Cochlear Implantation: The Variation in Cochlear Height.

This study aimed to identify the association between different cochlear metrics, including the basal turn diameter (A-value), the basal turn width (B-value), and the height of the cochlea (H-value). We also reported an association between H-value and hearing outcomes with cochlear implants (CI). This is a retrospective study that included all patients who underwent CI procedures between 2012 and 2018 at a tertiary center and have; preoperative high-resolution computed tomography (CT), normal cochlea, postoperative follow-up duration of at least 2 years, scores of the category auditory performance II (CAP-II), and speech intelligibility rating (SIR) scales. A total of 65 ears implanted with CI in 46 patients (24 boys and 20 girls; mean age of 7 (±10) years) fulfilled the inclusion criteria. We found significant positive correlations between A vs B, A vs H, and B vs H (P-value = 0.008, 0.018, and 0.0039, respectively). We also found a significant positive relationship between A, B, and H values and cochlear duct length (CDL) (P-value < 0.0001, 0.008, and 0.018, respectively). Finally, the H-value was significantly correlated with the SIR (P-value = 0.027). However, its correlation with the CAP score was not statistically significant (P-value = 0.62). Cochlear height significantly correlated with CDL and the other cochlear parameters. The variation in cochlear height can also affect speech outcomes in patients undergoing CI. Therefore, the H-value together with the other cochlear metrics should be adequately assessed preoperatively in CI patients.

Minimally invasive surgical techniques in vestibular function preservation in patients with cochlear implants.

BackgroundCochlear implantation (CI) is an effective and successful method of treating individuals with severe-to-profound sensorineural hearing loss (SNHL). Coupled with it’s great clinical effectiveness, there is a risk of vestibular damage. With recent advances in surgical approach, modified electrode arrays and other surgical techniques, the potential of hearing preservation (HP) has emerged, in order to preserve the inner ear function. These techniques may also lead to less vestibular damage. However, a systematic study on this at different follow-ups after CI surgery has not been documented before.AimsTo investigate changes of vestibular function systematically in recipients at short and long follow-ups after a minimally invasive CI surgery.MethodsIn this retrospective study, 72 patients (72 ears) with minimally invasive CI were recruited. All participants selected had bilateral SNHL and pre-operative residual hearing (RH) and underwent unilateral CI. They were treated to comprehensive care. All patients underwent vestibular function tests 5 days prior to CI. During the post-operative period, follow-up tests were performed at 1, 3, 6, 9, and 12 months. The contemporaneous results of caloric, cervical vestibular-evoked myogenic potential (cVEMP), ocular vestibular-evoked myogenic potential (oVEMP), and video head impulse (vHIT) tests were followed together longitudinally.ResultsOn the implanted side, the percent fail rate of caloric test was significantly higher than that of vHIT at 1, 3, and 9 months post-operatively (p < 0.05); the percent fail rate of oVEMP was higher than vHIT of superior semicircular canal (SSC), posterior semicircular canal (PSC), or horizontal semicircular canal (HSC) at 1, 3, and 9 months (p < 0.05); at 3 and 9 months, the percent fail rate of cVEMP was higher than that of SSC and PSC (p < 0.05). There were no significant differences in the percent fail rates among all tests at 6 and 12 months post-CI (p > 0.05). The percent fail rates showed decreased trends in caloric (p = 0.319) and HSC tested by vHIT (p = 0.328) from 1–3 to 6–12 months post-operatively. There was no significant difference in cVEMP between 1–3 and 6–12 months (p = 0.597). No significant differences on percent fail rates of cVEMP and oVEMP between short- and long-terms post-CI were found in the same subjects (p > 0.05). Before surgery, the abnormal cVEMP and oVEMP response rates were both lower in patients with enlarged vestibular aqueduct (EVA) than patients with a normal cochlea (p = 0.001, 0.018, respectively).ConclusionThe short- and long-term impacts on the vestibular function from minimally invasive CI surgery was explored. Most of the vestibular functions can be preserved with no damage discrepancy among the otolith and three semicircular canal functions at 12 months post-CI. Interestingly, a similar pattern of changes in vestibular function was found during the early and the later stages of recovery after surgery.

Auditory perception in pediatric cochlear implant users with cochlear nerve hypoplasia

ObjectivesThe objectives of this study were to assess auditory perception and speech intelligibility outcomes in children with cochlear nerve (CN) hypoplasia who received cochlear implants (CIs) using Categories of Auditory Performance II (CAP II) and Speech Intelligibility Rating (SIR) scales. MethodsIn total, 40 children who received CI and who were aged between 3 and 18 years were included in this study. The study group included 20 children with CN hypoplasia at least one ear, while the control group included 20 children with normal cochleas and cochlear nerve structures. All children in the study and control groups who participated were evaluated using the CAP II and the SIR scale. Demographic data were collected. ResultsSignificant differences were found between the study and control groups’ CAP II and SIR scores (p < 0.001). It was found that CAP II scores were positively correlated with SIR scores in the study (r = 0.743, p < 0.001) and control (r = 0.601, p < 0.001) groups. In the study group, significant negative correlations were found between SIR scores and age at implantation (r = −0.674, p = 0.004) and between CAP II scores and age at implantation (r = 0.751, p = 0.003). In the control group, a significant negative correlation was found between age at implantation and CAP II scores (r = −0.805, p = 0.001). Similarly, a significant negative correlation was found between age at implantation and SIR scores (r = −0.702, p = 0.007). ConclusionEven for children with severe inner ear malformation and CN hypoplasia, CI is an effective treatment modality for auditory perception and speech production. However, it should be noted that CN hypoplasia affects auditory performance negatively in children with CI.

Machine Learning-Based Prediction of the Outcomes of Cochlear Implantation in Patients With Cochlear Nerve Deficiency and Normal Cochlea: A 2-Year Follow-Up of 70 Children.

Cochlear nerve deficiency (CND) is often associated with variable outcomes of cochlear implantation (CI). We assessed previous investigations aiming to identify the main factors that determine CI outcomes, which would enable us to develop predictive models. Seventy patients with CND and normal cochlea who underwent CI surgery were retrospectively examined. First, using a data-driven approach, we collected demographic information, radiographic measurements, audiological findings, and audition and speech assessments. Next, CI outcomes were evaluated based on the scores obtained after 2 years of CI from the Categories of Auditory Performance index, Speech Intelligibility Rating, Infant/Toddler Meaningful Auditory Integration Scale or Meaningful Auditory Integration Scale, and Meaningful Use of Speech Scale. Then, we measured and averaged the audiological and radiographic characteristics of the patients to form feature vectors, adopting a multivariate feature selection method, called stability selection, to select the features that were consistent within a certain range of model parameters. Stability selection analysis identified two out of six characteristics, namely the vestibulocochlear nerve (VCN) area and the number of nerve bundles, which played an important role in predicting the hearing and speech rehabilitation results of CND patients. Finally, we used a parameter-optimized support vector machine (SVM) as a classifier to study the postoperative hearing and speech rehabilitation of the patients. For hearing rehabilitation, the accuracy rate was 71% for both the SVM classification and the area under the curve (AUC), whereas for speech rehabilitation, the accuracy rate for SVM classification and AUC was 93% and 94%, respectively. Our results identified that a greater number of nerve bundles and a larger VCN area were associated with better CI outcomes. The number of nerve bundles and VCN area can predict CI outcomes in patients with CND. These findings can help surgeons in selecting the side for CI and provide reasonable expectations for the outcomes of CI surgery.