Bony Cochlear Nerve Canal Research Articles

Anatomical Features of Children With Mondini Dysplasia: Influence on Cochlear Implantation Performance.

To analyze the long-term auditory performance after cochlear implantation (CI) and identify anatomical features of Mondini dysplasia associated with post-CI outcomes. Retrospective study. Tertiary care academic center. We enrolled 49 ears with Mondini dysplasia who underwent CI with more than 7 years of follow-up and age at CI- and sex-matched control group with radiologically normal inner ears. The development of auditory skills after CI was evaluated using word recognition scores (WRSs). The anatomical features were measured based on temporal bone computed tomography and magnetic resonance imaging, involving the width of the bony cochlear nerve canal (BCNC), cochlear basal turn, enlarged vestibular aqueduct, cochlear height, and diameter of the cochlear nerve (CN). CI in ears with Mondini dysplasia showed comparable benefits and improvement of auditory performance to controls during the 7 years of follow-up. In Mondini dysplasia, four (8.2%) ears showed narrow BCNC (<1.4 mm) with poorer WRS (58 ± 17%) than those with normal-sized BCNC, which had WRS (79 ± 10%) comparable to that of the control group (77 ± 14%). In Mondini dysplasia, the maximum ( r = 0.513, p < 0.001) and minimum ( r = 0.328, p = 0.021) CN diameters had positive correlations with post-CI WRS. The maximum CN diameter ( β = 48.347, p < 0.001) and BCNC width ( β = 12.411, p = 0.041) were significant factors that influence the post-CI WRS in multiple regression analysis. Preoperative anatomical evaluation, especially BCNC status and CN integrity, may serve as predictive markers for post-CI performance.

The effect of bony cochlear nerve canal (BCNC) diameter on the degree of sensorineural hearing loss.

This study investigated the correlation between the diameter of the bony cochlear nerve canal (BCNC), as determined by Temporal bone CT, and MRI findings of cochlear nerves (CN) in children with sensorineural hearing loss (SNHL). A prospective study design was followed. Radiological data (Temporal bone CT and MRI) of fifty children with sensorineural hearing loss (age <18y) were included in the study. All patients (100 ears) underwent routine MRI protocol in addition to 3D CISS (3-D constructive interference in steady state). Based on CT findings, the BCNC was classified according to its diameter into three groups; group 1 (<1.4mm), group 2 (1.4-2.0mm), and group 3 (>2.0mm). A significant difference between the three groups at degrees of SNHL (p<0.001) was observed. Significant difference (p<0.001) was also observed in the mean level of pure tone audiometry (PTA) average in group 1 compared to group 2. The CN was absent in 20 ears of group 1 CT results (29%), CN hypoplasia was noticed in 40 ears of group 1 CT (58%). However, CN was present in 9 ears of group 1 CT (13%), while in group 2 and 3, CN was present in 100% of the cases (27, and 4 ears, respectively, p<0.001). MRI and CT imaging are valuable in the diagnosis of SNHL in children. Moreover, with BCNC stenosis, there was a high probability of CN aplasia or hypoplasia.

Bony Cochlear Nerve Canal as a Predictor for Cochlear Nerve Status in Prelingually Deaf Children.

Objectives: The presence of a functional cochlear nerve is a key issue in the preoperative evaluation of pediatric candidates for cochlear implants. Correlations between cochlear nerve deficiency (CND) and bony abnormalities of the labyrinth or bony canal of the cochlear nerve are not yet well understood. The aim of this study was to determine whether the width of the bony cochlear canal (BCNC) can serve as a reliable predictive factor for the existence of a CND. Materials and methods: A total of 11 children with a confirmed diagnosis of prelingual, severe sensorineural hearing loss were included in this study. In all patients, indication for CI was confirmed and according to the preoperative protocol, high-resolution CT and MR were performed. Reconstructions at a distance of 0.6 mm of the axial plane and images from the HRCT of temporal bones were used for measuring the width of the BCNC. The cochlear nerves were evaluated on axial and sagittal - oblique T2 - MRI images and classified as normal, hypoplastic or aplastic. Two factors were reviewed retrospectively: the presence of inner ear anomalies and the relationship between BCNC stenosis and the existence of CND. Results: From a total of 22 temporal bones analyzed (22 ears in 11 patients), inner ear malformations were detected in 6 ears from 3 patients (27.27%). All three children had a bilateral malformation, in one it was Michel deformity and in two it was IP2 (incomplete partition 2). The BCNC diameter ranged from 0.1mm to 2.33mm with a mean value of 1.46±0.6mm. CND was recorded in 4 of 22 ears and all were associated with stenosis of the BCNC. In a total of three ears with a stenotic canal, we obtained a normal finding for the cochlear nerve on MR. Conclusion: Children with BCNC stenosis have a high incidence of CND. A narrowed BCNC on CT can be an indicator for the selection of children with sensorineural hearing loss who will need to be additionally referred for MRI in order to definitively assess the status of the cochlear nerve.

Heterozygous MYH9 Mutations in 2 Children With Cochlear Nerve Canal Stenosis.

MYH9 is a gene that encodes for a subunit of the myosin heavy chain IIA protein. Mutations in MYH9 are associated with hematologic abnormalities, renal dysfunction, and hearing loss. Bony cochlear nerve canal stenosis (CNCS), which is diagnosed on computed tomography (CT) imaging, has been associated with congenital deafness, cochlear nerve aplasia/hypoplasia, and inner ear malformations. We report two cases of CNCS presenting with profound congenital hearing loss whom we diagnosed with mutations in MYH9 and discuss the genotype-phenotype association and implications for management.

Do the Age of Implantation, the Widths of Internal Acoustic Canal and Bony Cochlear Nerve Canal Affect the Auditory Performance of Primary School Children with Bilateral Cochlear Implants?

Objective:To reveal the correlation between implantation age, the internal acoustic canal (IAC) width, bony cochlear nerve canal (BCNC) width, and auditory performance in primary school children with bilateral cochlear implantation (CI).Methods:Preoperative IAC and BCNC widths of 57 pre-lingually deaf children aged 7–11 years who had previously undergone bilateral CI in our institution were reviewed and cut-off values were calculated. Twenty-four patients who had additional problems and could not attend school and those who refused to participate in the study were excluded. The remaining 33 were invited to the hospital, and their speech perception tests, and language development scores were analyzed (16 of 33 patients had been operated on before the age of 24 months).Results:The cut-off values calculated from the 114 ears of 57 patients were 3.86 mm for IAC width and 1.56 mm for BCNC width. The auditory performances of the 33 patients after CI were not significantly different in the narrow and normal width groups. However, speech perception test results, and language development scores of patients implanted before the age of 24 months were significantly higher.Conclusion:There are some studies showing that children with bilateral sensorineural hearing loss have narrower IAC and BCNC widths. However, we concluded that the widths of the IAC and the bone cochlear nerve canal did not affect auditory performance. We found that implantation age is the single most important determinant of speech-language development after CI.

Investigating the association of electrically-evoked compound action potential thresholds with inner-ear dimensions in pediatric cochlear implantation

ObjectivesA narrow bony cochlear nerve canal (BCNC), as well as a hypoplastic and aplastic cochlear nerve (CN) have been associated with increased electrically-evoked compound action potential (eCAP) thresholds in some studies, suggesting poorer neural excitability in cochlear implantation. Also, in large cochleae the extent of activated spiral ganglion neurons with electrical stimulation is less than in smaller ones. However, a detailed description of the relationship between eCAP thresholds for a lateral-wall electrode array and dimensions of the inner-ear structures and internal auditory canal (IAC) is missing. DesignThe study subjects were 52 pediatric patients with congenital severe-to-profound hearing loss (27 females and 25 males; ages 0.7–2.0 years; 1.0 ± 0.3 years, mean ± SD) implanted bilaterally with Cochlear Nucleus CI422, CI522, or CI622 implants with full insertion of the Slim Straight electrode array. Diameters of the cochlea and the BCNC as well as the widths and heights of the IAC and the CN were evaluated from preoperative computed tomography and magnetic resonance images. These anatomical dimensions were compared with each other and with the patients’ intraoperative eCAP thresholds. ResultsThe eCAP thresholds increased from the apical to basal direction (r = 0.89, p < 0.001). After sorting the cochleae into four size categories, higher eCAP thresholds were found in larger than in smaller cochleae (p < 0.001). With similar categorization, the eCAP thresholds were higher in cochleae with a larger BCNC than in cochleae with a smaller BCNC (p < 0.001). Neither IAC nor CN cross-sectional areas affected the eCAP thresholds. Correlations were found between cochlea and BCNC diameters and between IAC and CN cross-sectional areas (r = 0.39 and r = 0.48, respectively, p < 0.001 for both). ConclusionsIn the basal part of the electrode array, higher stimulation levels to elicit measurable neural responses (eCAP thresholds) were required than in the apical part. Increased eCAP thresholds associated with a larger cochlear diameter, but contrary to the earlier studies, not with a small size of the BCNC or the CN. Instead, the BCNC diameter correlated significantly with the cochlea diameter.

Radiological spectrum of temporal bone, inner ear and brain parenchymal abnormalities in the preoperative cross-sectional imaging of sensorineural hearing loss in cochlear implant candidates: A prospective study

Cochlear implantation is a prudent method of rehabilitation in severe sensorineural hearing loss where other means like hearing aids fail. Not everybody with severe sensorineural hearing loss benefits from implantation, in fact is contraindicated in some. A thorough pre-surgical imaging evaluation of inner ear, temporal bone and cerebral parenchyma is important in decision making, more so as the implants and costs involved are quite expensive. Limited studies exist in the Indian setting. Aim was to evaluate the role of combined computed tomography (CT) and Magnetic Resonance imaging (MRI) in pre operative imaging assessment for cochlear implantation, a prospective study was concluded at the Department of Radiodiagnosis over 30 months (2017 to 2019). Patients with severe hearing loss underwent HRCT temporal bone on 128 slice MDCT and MRI with BFFE, T2/Flair etc. Sequences targeting inner ear, cochlear nerve and brain on 3 Tesla scanner. Data was entered in MS EXCEL and analyzed in SPSS software using cross tabulations or correlation coefficient to compare the two imaging modalities. Chi square and P values were obtained for the cross tabulation data of comparison of CT and MRI in assessment of inner ear structures. The study focused on cochleovestibular malformations, patency of the cochlea-vestibule, cochlear nerve status on MRI and to see if there was any correlation with the bony cochlear nerve canal diameter on CT, isolated or associated brain parenchymal abnormalities and important surgical access criteria like normal variants and altered middle ear anatomy. Abnormal imaging findings were seen in 15 of 32 patients, on the basis of which 5 were rejected for implantation; suboptimal results were predicted in 5 other abnormal cases. Side selection and predicting ease of electrode insertion could also be ascertained in unilateral pathologies. Seventeen cases had normal imaging, twelve of which were operated. Eleven of these had uneventful surgery. All three cases with abnormal imaging, taken for surgery under varied risk of suboptimal results had mild and manageable intraoperative complications. Tailored protocol of MRI with BFFE, T2/FLAIR axials and HRCT temporal bone is an indispensable tool and radiologist plays key role in candidate selection and exclusion, surgical planning and warning surgeon about potential intraoperative complications in cochlear implant surgery.

Bony cochlear nerve canal in children with bilateral profound sensorineural hearing loss – a pilot study

Introduction: The aim of this study was to evaluate the width of the bony cochlear nerve canal (BCNC) in children with congenital sensorineural hearing loss (SNHL) and "normal" findings on thin section temporal bone CT. Material and methods: The width of the BCNC was retrospectively evaluated in two groups of patients. The study group included 11 children (22 bone canals) aged 2-12 years, with congenital, bilateral SNHL who underwent cochlear implantation (CI) from July to De­cember 2019 and no abnormalities of the inner ear were detected on their preoperative CT scans. Eleven patients (22 bone canals), aged 3-10 years, in whom no sensorineural hearing loss had been diagnosed were taken as controls and CT scan of the temporal bone was perfor­med for another reason - suspected acute mastoiditis, chronic otitis media, or perforation of the tympanic membrane. Axial sections of their CT scans were used to measure the width of the BCNC. Results: BCNC width values in patients with bilateral, profound sensorineural hearing loss ranged from 1.0 to 2.3 mm and the mean value was 1.5±0.3 mm. In patients with normal hearing, the values for the canal width were higher, with mean value of 2.1±0.3 mm. Conclusion: The results obtained showed that the width of the BCNC in children with bilateral, profound sensorineural hearing impairment was significantly smaller than in the con­trol group with normal hearing for p &lt;0.05 (t-test=6.62912, p=0.000000).

Auditory and speech performance after unilateral cochlear implantation for cochlear nerve canal stenosis.

To explore the correlation between the width of the bony cochlear nerve canal (CNC) and long-term auditory rehabilitation after unilateral cochlear implantation (CI) in pediatric patients with congenital deafness and bilateral cochlear nerve canal stenosis (CNCS). A retrospective review was performed on 10 patients with bilateral CNCS and bilateral congenital profound hearing loss who each underwent unilateral cochlear implantation. The width of the CNC was determined on computed tomography (CT) imaging and following CI, auditory and speech performance following CI were graded using categories of auditory performance (CAP), speech intelligibility rating (SIR), and the meaningful auditory integration scale (MAIS) at 24 months following implantation. No correlation was noted between CAP score and CNCS at 24 months post CI (P > .05). A positive correlation was noted between SIR score and CNC width (ρ = .81, P < .05). Similarly, a positive correlation was noted between MAIS and CNC width (ρ = .71, P < .05). The width of the CNC in patients with CNCS is positively correlated with some long-term auditory and speech outcomes after CI.

Cochlear Nerve Canal Stenosis: Association With MYH14 and MYH9 Genes.

The bony cochlear nerve canal transmits the cochlear nerve as it passes from the fundus of the internal auditory canal to the cochlea. Stenosis of the cochlear nerve canal, defined as a diameter less than 1.0 mm in transverse diameter, is associated with inner ear anomalies and severe to profound congenital hearing loss. We describe an 11-month-old infant with nonsyndromic congenital sensorineural hearing loss with cochlear nerve canal stenosis. Next-generation sequencing revealed heterozygous mutations in MYH9 and MYH14, encoding for the inner ear proteins myosin heavy chain IIA and IIC. The patient's hearing was rehabilitated with bilateral cochlear implantation.

Anatomical and Pathological Findings of Magnetic Resonance Imaging in Idiopathic Sudden Sensorineural Hearing Loss.

Background and ObjectivesWe sought to evaluate the diagnostic and prognostic value of measurable parameters of internal auditory canal (IAC) magnetic resonance imaging (MRI) in patients with idiopathic sudden sensorineural hearing loss (ISSNHL).Subjects and MethodsWe retrospectively reviewed the patients with ISSNHL who underwent IAC MRI from January 2008 to March 2019. Measurable parameters of IAC MRI, such as the diameter of the IAC, bony cochlear nerve canal, and cross-sectional area of the cochlear nerve, were measured by a single examiner. These parameters were then compared between the affected and healthy sides. Inner-ear abnormalities such as intralabyrinthine hemorrhage or labyrinthitis were also evaluated. The relationship between the surveyed parameters and the diagnosis of ISSNHL was assessed.ResultsA total of 208 patients with ISSNHL were included. The measured parameters of IAC MRI were not different between the affected and healthy sides and were also not associated with the diagnosis of ISSNHL. However, inner-ear abnormalities of IAC MRI in ISSNHL displayed a significant association with worse hearing before and after treatment. An age that was older than 40 years also correlated with poorer outcomes. Further, inner-ear abnormalities were more frequently detected when IAC MRI was performed early after ISSNHL onset.ConclusionsPatients with ISSNHL and inner ear abnormalities such as intralabyrinthine hemorrhage or labyrinthitis identified via IAC MRI may experience poorer hearing outcomes. To detect such abnormal findings, it is recommended to perform IAC MRI early after the onset of ISSNHL.

Outcome of Cochlear Implantation in Children With Narrow Bony Cochlear Nerve Canal.

To investigate the diameter of the bony cochlear nerve canal (BCNC) as a prognostic indicator of cochlear implantation (CI) in children. Retrospective study. Tertiary referral center. Two hundred ninety two prelingual deaf children (323 ears) who received CI before the age of 5 years. CI in pediatric patients. Postoperative auditory performance was analyzed according to the diameter of the BCNC using the Mann-Whitney U test. Using the images of temporal bone computed tomography, patients were grouped according to the diameter of the BCNC: narrow (<1.4 mm, Group 1), normal (Group 2), and other anomalies (Group 3). Group 1 (10.5%) showed a less significant degree of improvement in category of audiological performance (CAP) score than Groups 2 (57.3%) and 3 (32.2%). Scores obtained from both the open-set monosyllabic words and sentence tests were lower in Group 1 than Groups 2 and 3. Of the patients with narrow BCNC, the CAP score of patient with complete stenosis of BCNC (<0.2 mm) was lower than that of patients with BCNC between 0.2 and 0.8 mm, also 0.8 and 1.4 mm. The improvement in auditory performance was limited in children with narrow BCNC and the narrower the BCNC, the more severe the limitation. However, gradual improvement can be expected and even children with narrow BCNC may be candidates for early CI and rehabilitation.

A Case of Congenital Bifurcation of the Labyrinthine Segment of Facial Nerve

The most common anomaly of facial nerve is bony dehiscence of the fallopian canal, being present in approximately 55% of the population. Abnormal courses of facial nerve are reported commonly. Of the malformation of the facial nerve, bifurcation of its intratemporal portion has been rarely reported, in which one or more segments of the facial nerve splits. Nine years-old girl (right-handed) came to our outpatient clinic for left hearing loss, which was incidentally found by herself. Audiologic and radiologic work-up demonstrated unilateral sensorineural hearing loss, which was resulted from the narrow bony cochlear nerve canal, and incidentally found the bifurcation of the labyrinthine segment of ipsilateral facial nerve. We described characteristic findings on the computed tomogram of this anomaly and discussed it. It is important to identify the anomalous facial nerve in the patients undergoing evaluation for congenital hearing loss. (J Clinical Otolaryngol 2019;30:83-87)

Clinical Value of Measurement of Internal Auditory Canal in Pediatric Cochlear Implantation.

The aims of this study were to clarify the clinical value of the bony cochlear nerve canal (BCNC) and internal auditory canal (IAC) in children with bilateral sensorineural hearing loss (b-SNHL) and to reveal the correlation between these parameters and outcomes after cochlear implantation (CI). Ninety-four ears with b-SNHL that received CI and 100 ears with normal hearing were enrolled. Parameters of IAC and pre- and post-CI categories of auditory performance scores were analyzed. The width of the BCNC and the width, height, and length of the IAC were shorter in the b-SNHL group. BCNC and IAC width were associated with b-SNHL. The calculated cutoff values for BCNC and IAC width were 2.055 mm in the BCNC and 4.245 mm in the IAC, setting the sensitivity to 90%. Patients with narrow BCNCs and IACs had significantly worse post-CI auditory performance. BCNC and IAC widths were narrower in children with b-SNHL than in normal-hearing children. Narrow BCNC and IAC width had a negative impact on post-CI outcomes. The proposed cutoff values for BCNC and IAC width were meaningful when predicting the auditory outcome after CI, especially considering both.

Duplicated Internal Auditory Canal: High-Resolution CT and MRI Findings.

ObjectiveTo summarize the high-resolution computed tomography (HRCT) and magnetic resonance imaging (HRMRI) features of duplicated internal auditory canals (DIACs).Materials and MethodsEar HRCT data of 64813 patients with sensorineural hearing loss (SNHL), obtained between August 2009 and November 2017, were reviewed. Among these patients, 12 (13 ears) were found to have DIACs, 9 of whom underwent HRMRI. Their images were evaluated by two otoradiologists.ResultsThe rate of occurrence of DIAC among SNHL patients was 0.019% (12/64813). The internal auditory canals of 13 ears were divided into double canals by complete (n = 6) and incomplete (n = 7) bony septa, with varied orientations ranging from horizontal to approximately vertical. All of the anterosuperior canals extended into the facial nerve (FN) canal, except for 1, which also extended to the vestibule. The posteroinferior canals ended in the cochlea and vestibule, except for 2, which also connected to the FN canals. Magnetic resonance images revealed that 77.8% (7/9) and 22.2% (2/9) of vestibulocochlear nerves (VCNs) were aplastic and hypoplastic, respectively. Furthermore, 88.9% (8/9) of FNs were normal, except for 1, which was hypoplastic. All of the affected ears also had other ear anomalies: a narrow, bony cochlear nerve canal was the most common other anomaly, accounting for 92.3% (12/13). Malformations of other systems were not found.ConclusionDouble-canal appearance is a characteristic finding of DIAC on HRCT, and it is usually accompanied by other ear anomalies. The VCN usually appears aplastic, with a normal FN, on HRMRI.

Bony cochlear nerve canal stenosis in pediatric unilateral sensorineural hearing loss

ObjectivesThis study was performed to evaluate the frequency of bony cochlear nerve canal (BCNC) stenosis and its clinical significance in pediatric patients with unilateral sensorineural hearing loss (SNHL) of unknown etiology. Materials and methodsWe analyzed the medical records and temporal bone computed tomography (CT) results of patients less than 13 years of age with a diagnosis of unilateral SNHL of unknown etiology between July 2007 and July 2017. We compared the BCNC diameter between both sides and analyzed the age at diagnosis, degree of hearing loss, and accompanying inner ear anomalies. ResultsIn 42 patients, the mean age at diagnosis was 7.4 ± 3.6 years, and the average hearing level in the affected ear was 87.9 ± 20.0 dB HL (decibels hearing level). The average diameter of the BCNC was 1.22 ± 0.75 mm on the affected side and 1.96 ± 0.52 mm on the normal side. The most suitable criterion for BCNC stenosis appeared to be a diameter of 1.2 mm by the recursive partitioning procedure. With application of this criterion, the rate of BCNC stenosis was significantly greater on the affected side than on the normal side (52.4% vs. 4.8%, respectively; P < 0.05). A narrow internal acoustic canal was found in two patients, and vestibular and cochlear anomalies were found in three patients each. ConclusionsOur results suggest that it is reasonable to set a diameter of 1.2 mm as a cutoff for BCNC stenosis, and also that BCNC stenosis is a common cause of unilateral SNHL of unknown etiology in childhood.

Does the Width of the Bony Cochlear Nerve Canal Predict the Outcomes of Cochlear Implantation?

A narrow bony cochlear nerve canal (BCNC) is associated with sensorineural hearing loss necessitating cochlear implantation (CI). This study evaluated the implications of BCNC width for post-CI outcomes. A total of 56 children who had received CIs were included. The patients were divided into three groups according to the width of the BCNC (Group 1: diameter < 1.4 mm, n = 17; Group 2: diameter 1.4–2.0 mm, n = 14; Group 3: diameter > 2.0 mm, n = 25). The post-CI speech performances were compared among the three groups according to BCNC width. The correlation between BCNC width and post-CI speech performance was evaluated. Logistic regression analysis was also performed to investigate factors that can impact post-CI speech performance. Cochlear nerve deficiency (CND) occurred more frequently in Group 1. Groups 1 and 2 had significantly worse post-CI outcomes. Patients with intact cochlear nerves had significantly better post-CI outcomes than those with CND. When the cochlear nerve was intact, patients with a narrower BCNC showed less favorable results. Therefore, patients with either a narrow BCNC or CND seemed to have poorer outcomes. A narrow BCNC is associated with higher CND rates and poor outcomes. Measurement of BCNC diameter may help predict CI outcomes.

Progression of Unilateral Hearing Loss in Children With and Without Ipsilateral Cochlear Nerve Canal Stenosis: A Hazard Analysis.

To investigate the risk of hearing loss progression in each ear among children with unilateral hearing loss associated with ipsilateral bony cochlear nerve canal (BCNC) stenosis. Tertiary pediatric referral center. Children diagnosed with unilateral hearing loss who had undergone temporal bone computed tomography imaging and had at least 6 months of follow-up audiometric testing were identified from a prospective audiological database. Two pediatric radiologists blinded to affected ear evaluated imaging for temporal bone anomalies and measured bony cochlear canal width independently. All available audiograms were reviewed, and air conduction thresholds were documented. Progression of hearing loss was defined by a 10 dB increase in air conduction pure-tone average. One hundred twenty eight children met inclusion criteria. Of these, 54 (42%) had a temporal bone anomaly, and 22 (17%) had ipsilateral BCNC stenosis. At 12 months, rates of progression in the ipsilateral ear were as follows: 12% among those without a temporal bone anomaly, 13% among those with a temporal bone anomaly, and 17% among those with BCNC stenosis. Children with BCNC stenosis had a significantly greater risk of progression in their ipsilateral ear compared with children with no stenosis: hazard ratio (HR) 2.17, 95% confidence interval (CI) (1.01, 4.66), p value 0.046. When we compared children with BCNC stenosis to those with normal temporal bone imaging, we found that the children with stenosis had nearly two times greater risk estimate for progression, but this difference did not reach significance, HR 1.9, CI (0.8, 4.3), p = 0.1. No children with BCNC stenosis developed hearing loss in their contralateral year by 12 months of follow-up. Children with bony cochlear nerve canal stenosis may be at increased risk for progression in their ipsilateral ear. Audiometric and medical follow-up for these children should be considered.

Bony cochlear nerve canal and internal auditory canal measures predict cochlear nerve status.

The bony cochlear nerve canal is the space between the fundus of the internal auditory canal and the base of the cochlear modiolus that carries cochlear nerve fibres. This study aimed to determine the distribution of bony labyrinth anomalies and cochlear nerve anomalies in patients with bony cochlear nerve canal and internal auditory canal atresia and stenosis, and then to compare the diameter of the bony cochlear nerve canal and internal auditory canal with cochlear nerve status. The study included 38 sensorineural hearing loss patients (59 ears) in whom the bony cochlear nerve canal diameter at the mid-modiolus was 1.5 mm or less. Atretic and stenotic bony cochlear nerve canals were examined separately, and internal auditory canals with a mid-point diameter of less than 2 mm were considered stenotic. Temporal bone computed tomography and magnetic resonance imaging scans were reviewed to determine cochlear nerve status. Cochlear hypoplasia was noted in 44 out of 59 ears (75 per cent) with a bony cochlear nerve canal diameter at the mid-modiolus of 1.5 mm or less. Approximately 33 per cent of ears with bony cochlear nerve canal stenosis also had a stenotic internal auditory canal and 84 per cent had a hypoplastic or aplastic cochlear nerve. All patients with bony cochlear nerve canal atresia had cochlear nerve deficiency. The cochlear nerve was hypoplastic or aplastic when the diameter of the bony cochlear nerve canal was less than 1.5 mm and the diameter of the internal auditory canal was less than 2 mm. The cochlear nerve may be aplastic or hypoplastic even if temporal bone computed tomography findings indicate a normal cochlea. If possible, patients scheduled to receive a cochlear implant should undergo both computed tomography and magnetic resonance imaging of the temporal bone. The bony cochlear nerve canal and internal auditory canal are complementary structures, and both should be assessed to determine cochlear nerve status.

Prediction of Cochlear Implant Outcomes in Patients With Prelingual Deafness.

Objectives.To evaluate the factors that limit post-cochlear implantation (CI) speech perception in prelingually deaf children.Methods.Patients with CI were divided into two groups according to Category of Auditory Performance (CAP) scores 3 years post-CI: the poor performance group (poor performance group, CAP scores≤4, n=41) and the good performance group (good performance group, CAP scores≥5, n=85). The distribution and contribution of the potential limiting factors related to post-CI speech perception was compared.Results.Perinatal problems, inner ear anomalies, narrow bony cochlear nerve canal (BCNC), and intraoperative problems was significantly higher in the poor performance group than the good performance group (P=0.010, P=0.003, P=0.001, and P=0.045, respectively). The mean number of limiting factors was significantly higher in the poor performance group (1.98±1.04) than the good performance group (1.25±1.11, P=0.001). The odds ratios for perinatal problems and narrow bony cochlear nerve canal in the poor performance group in comparison with the good performance group were 4.878 (95% confidence interval, 0.067 to 0.625; P=0.005) and 4.785 (95% confidence interval, 0.045 to 0.972; P=0.046).Conclusion.This study highlights the comprehensive prediction of speech perception after CI and provides otologic surgeons with useful information for individualized preoperative counseling of CI candidates.