Dimensions of the cochlear nerve canal: a radioanatomic investigation

Brazilian Society of Otology task force - single sided deafness - recommendations based on strength of evidence

OBJECTIVE

To make evidence-based recommendations for the treatment of Single-Sided Deafness (SSD) in children and adults.

METHODS

Task force members were instructed on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on SSD were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions.

RESULTS

The topics were divided into 3 parts: (1) Impact of SSD in children; (2) Impact of SSD in adults; and (3) SSD in patients with temporal bone tumors.

CONCLUSIONS

Decision-making for patients with SSD is complex and multifactorial. The lack of consensus on the quality of outcomes and on which measurement tools to use hinders a proper comparison of different treatment options. Contralateral routing of signal hearing aids and bone conduction devices can alleviate the head shadow effect and improve sound awareness and signal-to-noise ratio in the affected ear. However, they cannot restore binaural hearing. Cochlear implants can restore binaural hearing, producing significant improvements in speech perception, spatial localization of sound, tinnitus control, and overall quality of life. However, cochlear implantation is not recommended in cases of cochlear nerve deficiency, a relatively common cause of congenital SSD.

High Prevalence of Cochlear Nerve Deficiency in Pediatric Patients With Cochlear Aperture Stenosis

OBJECTIVE

Cochlear nerve deficiency (CND) is a common radiologic finding among unilateral sensorineural hearing loss (USNHL) patients. It is generally detected with magnetic resonance imaging (MRI), which is associated with higher cost, less availability, and possible need for sedation. Therefore, identifying computed tomography (CT) findings, such as cochlear aperture stenosis (CAS), that can reliably predict CND is valuable. Our study aimed to determine the prevalence of CND in pediatric patients with CT-diagnosed CAS.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary care center.

METHODS

We included pediatric patients diagnosed with CAS on temporal bone CT and with available temporal bone MRI. For each patient, an otolaryngologist and a pediatric neuroradiologist measured the cochlear aperture width on CT to confirm CAS (cochlear aperture < 1.4 mm) and assessed the status of the cochlear nerve on MRI.

RESULTS

Fifty-five patients, representing 65 ears, had CAS on CT measurement. Median cochlear aperture width in CAS ears was 0.70 mm (interquartile range [IQR]: 0.40-1.05 mm) versus 2.00 mm in non-CAS ears (IQR: 1.80-2.30 mm, P < .001). CND was found in 98.5% (n = 64/65) of CAS ears, while a normal cochlear nerve was found in 1.5% (n = 1/65) of CAS ears.

CONCLUSION

CND is highly prevalent among pediatric patients with CAS. This suggests that MRI may not be needed to assess for CND in USNHL patients with CAS, as initial CT may provide sufficient information to determine cochlear implant candidacy. We recommend thoughtful shared decision-making with parents of USNHL patients when determining whether to pursue MRI in the setting of a CAS diagnosis.

Clinical Portrait of Cochlear Implantation in Patients With CHARGE Syndrome

OBJECTIVE

To examine the clinical characteristics and auditory performance of patients with CHARGE syndrome following cochlear implantation (CI), as well as the prognostic factors affecting auditory outcomes.

STUDY DESIGN

Retrospective cohort.

SETTING

Tertiary academic center.

METHODS

A retrospective chart review was performed in patients with CHARGE syndrome who underwent CI from 2007 to 2022. The category of auditory performance (CAP) score was used to assess the CI outcomes, and factors that may affect the speech outcomes were also evaluated.

RESULTS

In 14 children with CHARGE syndrome, 22 CIs were performed, 6 unilaterally and 8 bilaterally. The mean age at CI was 25.9 months (range: 10-62). All patients had ear abnormalities and developmental delays, and cochlear nerve deficiency (CND) was present in all ears. At the last follow-up (mean: 49.6 months), the mean CAP score improved significantly compared to the preoperative measure (from 0.36 ± 0.81 to 3.21 ± 1.70, P = .001), with 6 patients (42.9%) achieving a CAP score of 4 points or higher. However, between the unilateral and bilateral CI groups, the final CAP score or change in CAP score was similar. Factors including age, coloboma, and CND did not significantly affect speech outcomes (all P > .05).

CONCLUSION

Even though CHARGE syndrome features challenging anomalies, CI can be conducted safely and can offer effective contribution to significant speech improvement. Patients with CHARGE syndrome should be given the opportunity to undergo CI to maximize their audiological progress.

Non-Syndromic Sensorineural Hearing Loss in Children

Pediatric hearing loss is common with significant consequences in terms of language, communication, social and emotional development, and academic advancement. Radiological imaging provides useful information regarding hearing loss etiology, prognosis, therapeutic options, and potential surgical pitfalls. This review provides an overview of temporal bone imaging protocols, an outline of the classification of inner ear anomalies associated with sensorineural hearing loss and illustrates some of the more frequently encountered and/or important causes of non-syndromic hearing loss.

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

PURPOSE

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).

MATERIALS AND METHODS

A prospective study design was followed. Radiological data (Temporal bone CT and MRI) of fifty children with sensorineural hearing loss (age <18 y) 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).

RESULTS

Based on CT findings, the BCNC was classified according to its diameter into three groups; group 1 (<1.4 mm), group 2 (1.4-2.0 mm), and group 3 (>2.0 mm). 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).

CONCLUSIONS

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.

[Prospects for cochlear implantation in patients with auditory nerve dysplasia]

Auditory nerve dysplasia (AND) can encompass various conditions of the auditory nerve (AN), ranging from true aplasia to hypoplasia. The purpose of this review is to discuss the prospect of cochlear implantation (CI) and subsequent auditory speech rehabilitation for AN abnormality. Studies of different authors when working with this category of children, possible results and methods of diagnostics of the AN condition are presented.

Diameter of the Cochlear Nerve Canal predicts Cochlear Nerve Deficiency in Children with Sensorineural Hearing Loss

PURPOSE

 Detection of cochlear nerve deficiency (CND) is usually straightforward using magnetic resonance imaging (MRI). In patients in whom MRI cannot be performed or imaging provides equivocal findings, computed tomography (CT) of the temporal bone might offer indirect evidence of CND. Our study aimed to derive a cut-off value for the diameter of the cochlear nerve canal (CNC) and internal auditory canal (IAC) in temporal bone CT to predict CND.

MATERIALS AND METHODS

 This retrospective study included 70 children with sensorineural hearing loss (32 with CND and 38 control patients). The height, width, and cross-sectional area of the IAC and diameter of the CNCs were determined using temporal bone CT. Receiver operating characteristic (ROC) and Student's t-tests were performed for each parameter.

RESULTS

 The mean diameter of the CNCs was significantly smaller in children with CND than in the control group (1.2 mm versus 2.4 mm, p < .001). The optimal threshold for CNC for separation of the two groups was 1.9 mm, resulting in a sensitivity of 98.7 % and specificity of 89.2 %. The IAC dimensions could not distinguish between children with CND and controls.

CONCLUSION

 A CNC diameter of less than 1.9 mm is a reliable predictor of CND in children with sensorineural hearing loss.

KEY POINTS

  · A small cochlear nerve canal predicts cochlear nerve deficiency (CND). · The size of the internal auditory canal cannot predict CND. · Whenever MRI is impossible or ambigous, CT can rule out CND.

CITATION FORMAT

· Sorge M, Sorge I, Pirlich M et al. Diameter of the Cochlear Nerve Canal predicts Cochlear Nerve Deficiency in Children with Sensorineural Hearing Loss. Fortschr Röntgenstr 2022; DOI: 10.1055/a-1826-0641.

Re-Examining the Cochlea in Branchio-Oto-Renal Syndrome: Genotype-Phenotype Correlation

BACKGROUND AND PURPOSE

Temporal bone imaging plays an important role in the work-up of branchio-oto-renal syndrome. Previous reports have suggested that the unwound or offset cochlea is a highly characteristic marker for branchio-oto-renal syndrome. Our goals were to examine the prevalence of this finding in a branchio-oto-renal syndrome cohort and analyze genetic-phenotypic associations not previously established.

MATERIALS AND METHODS

This multicenter retrospective study included 38 ears in 19 unrelated individuals with clinically diagnosed branchio-oto-renal syndrome and confirmed mutations in the EYA1 or SIX1 genes. Two blinded neuroradiologists independently reviewed and documented temporal bone imaging findings in 13 categories for each ear. Imaging phenotypes were correlated with genotypes.

RESULTS

There was excellent interrater agreement for all 13 phenotypic categories (κ ≥ 0.80). Of these, 9 categories showed statistically significant differences between patients with EYA1-branchio-oto-renal syndrome and SIX1-branchio-oto-renal syndrome. Cochlear offset was present in 100% of patients with EYA1-branchio-oto-renal syndrome, but in only 1 ear (12.5%) among patients with SIX1-branchio-oto-renal syndrome. A short thorny appearance of the cochlear apical turn was observed in most patients with SIX1-branchio-oto-renal syndrome.

CONCLUSIONS

An offset cochlea is associated with the EYA1-branchio-oto-renal syndrome genotype. The SIX1-branchio-oto-renal syndrome genotype is associated with a different cochlear phenotype that almost always is without offset and has a short thorny tip as the apical turn. Therefore, cochlear offset is not a characteristic marker for all patients with branchio-oto-renal syndrome. The lack of a cochlear offset in a patient with clinically suspected branchio-oto-renal syndrome does not exclude the diagnosis and, in fact, may be predictive of the SIX1 genotype.

Does size of the cochlear nerve affect postoperative auditory performance in pediatric cochlear implant patients with normal cochlear nerves?

Introduction

Cochlear implantation is an effective treatment method for severe to profound hearing loss. Many factors that may influence cochlear implantation success have been explained in previous studies. Apart from those, minor differences in size of normal cochlear nerves may affect postoperative performance.

Objective

To investigate whether the minor differences in cochlear nerve size in normal cochlear nerves affect postoperative cochlear implant performance.

Methods

30 pediatric prelingually deaf patients who were treated with cochlear implantation were included in this study. From the reconstructed parasagittal magnetic resonance images, the diameter and cross-sectional area of the cochlear nerve on the ipsilateral and contralateral side were measured. Auditory evaluations were performed 1, 3, 6 and 12 months following the first fitting. All the analysis was performed by using EARS®, evaluation of auditory responses to speech tool. Correlation between cochlear nerve diameter, cross-sectional area and postoperative auditory perception was analyzed to determine whether variation in cochlear nerve size contributes to postoperative auditory performance.

Results

The mean diameter of the cochlear nerve on the ipsilateral side was 718.4 μm (504.5 − 904.3 μm) and mean cross sectional area was 0.015 cm² (0.012 − 0.018 cm²). On the contralateral side the mean cochlear nerve diameter was 714.4 μm (502.6 − 951.4 μm) and mean cross sectional area was 0.014 cm² (0.011 − 0.019 cm²). The correlation between the diameter and cross-sectional area of the ipsilateral and contralateral cochlear nerve revealed no significance. Mean score at first month monosyllable-trochee-polysyllable test, MTP1, was 0.17 (0.08 − 0.33), at 6th month with 6 words test, 6th month MTP6 was 0.72 (0.39 − 1.0), at 6th month with 12 words, 6th month MTP 12 was 0.46 (0.17 − 0.75) and at 12th month with 12 words, 12th month MTP12 was 0.73 (0.25 − 1.0). There was no correlation between the monosyllable-trochee-polysyllable test, values at any time with the diameter of the ipsilateral cochlear nerve. However, the first month MTP, 6th month MTP6 and 12th month MTP12 correlated with the cross-sectional area of the ipsilateral cochlear nerve.

Conclusion

Measuring the cross sectional area of the normal- appearing cochlear nerve may give important prognostic knowledge on cochlear implant outcomes. In patients with a larger cross sectional area the auditory performance was better and faster. Although normal appearing, slight differences on cross sectional area of the cochlear nerve may affect performance. Measuring the size of the cochlear nerve on parasagittal magnetic resonance images may provide beneficial information on the postoperative rehabilitation process.

Cochlear nerve canal stenosis and associated semicircular canal abnormalities in paediatric sensorineural hearing loss: a single centre study

OBJECTIVE

This study aimed to evaluate the association between cochlear nerve canal dimensions and semicircular canal abnormalities and to determine the distribution of bony labyrinth anomalies in patients with cochlear nerve canal stenosis.

METHOD

This was a retrospective study in which high-resolution computed tomography images of paediatric patients with severe-to-profound sensorineural hearing loss were reviewed. A cochlear nerve canal diameter of 1.5 mm or less in the axial plane was classified as stenotic. Semicircular canals and other bony labyrinth morphology and abnormality were evaluated.

RESULTS

Cochlear nerve canal stenosis was detected in 65 out of 265 ears (24 per cent). Of the 65 ears, 17 ears had abnormal semicircular canals (26 per cent). Significant correlation was demonstrated between cochlear nerve canal stenosis and semicircular canal abnormalities (p < 0.01). Incomplete partition type II was the most common accompanying abnormality of cochlear nerve canal stenosis (15 out of 65, 23 per cent).

CONCLUSION

Cochlear nerve canal stenosis is statistically associated with semicircular canal abnormalities. Whenever a cochlear nerve canal stenosis is present in a patient with sensorineural hearing loss, the semicircular canal should be scrutinised for presence of abnormalities.

Single-sided deafness after sudden hearıng loss: late effect on cochlear nerve size

PURPOSE

Single-sided deafness (SSD) is a condition where an individual has non-functional hearing in one ear and receives no clinical benefit from amplification in that ear, with the contralateral ear possessing normal audiometric function. Cochlear implant presents a good choice in rehabilitation of SSD. The presence of a deficient cochlear nerve (CN) has been linked to poor performance with cochlear implants. CN can be measured by imaging techniques. The objective of this study was to compare CN diameter in patients who had a history of single-sided deafness because of sudden hearing loss.

METHODS

Retrospective study where radiologist was blind designed. 53 SSD patients who had a history of sudden hearing loss and MRI at least 5 years after the sudden hearing loss were included in this retrospective study. High-resolution 3-D constructive interference in steady state (CISS)-sequence magnetic resonance (MRI) images was review by the neurotology-experienced blind radiologist. Vertical, horizontal and area measurements of cochlear nerve between the deaf and the normal ear were made.

RESULTS

There was no statistically significant difference between the normal ear and deaf ear of the subjects in terms of cochlear nerve vertical diameter, horizontal diameter and area. (respectively, p = 0.250; p = 0.183; p = 0.874) CONCLUSION: The numbers of remaining cochlear neurons and spiral ganglion cells in the implanted deaf ears are critical and evidence was not found for spiral ganglion cell loss in the sudden hearing loss deaf ear with SSD in MRI. In the light of all these findings, implantation would be a good choice for rehabilitation in postlingual SSD regardless of auditory deprivation duration.

Novel Computed Tomography Findings Suggestive of Perilymph Gusher

OBJECTIVES

Perilymphatic gusher (PLG) is an uncommon complication of stapedectomy and cochlear implant placement. Computerized tomography (CT) may reveal congenital dysplasia responsible for PLG but may also be (incorrectly) interpreted as normal. The aim of this study was to review CT findings in patients with PLG reported to have normal temporal bones.

PATIENTS

Patients in which a PLG was encountered and preoperative CT imaging had been interpreted as normal.

INTERVENTION

Collaborative review of temporal bone computed tomography by neurotologist and neuroradiologist.

MAIN OUTCOME MEASURE

Identification of undetected inner ear anomalies that may predispose to PLG.

RESULTS

Unanticipated PLG was encountered during stapes surgery in two patients and cochlear implantation in one. A focal bony dehiscence between the basal turn of the cochlea and internal auditory canal (IAC) was identified on a few oblique reformatted images in all patients.

CONCLUSIONS

High resolution CT with oblique image reformatting is essential to identify focal communication between the IAC and basal turn of the cochlea in ears with PLG.

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

OBJECTIVE

To investigate the diameter of the bony cochlear nerve canal (BCNC) as a prognostic indicator of cochlear implantation (CI) in children.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

PATIENTS

Two hundred ninety two prelingual deaf children (323 ears) who received CI before the age of 5 years.

INTERVENTIONS

CI in pediatric patients.

MAIN OUTCOME AND MEASURES

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).

RESULTS

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.

CONCLUSIONS

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.

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

OBJECTIVES

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).

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Assessment of the Clinical Benefit of Imaging in Children With Unilateral Sensorineural Hearing Loss: A Systematic Review and Meta-analysis

IMPORTANCE

Imaging used to determine the cause of unilateral sensorineural hearing loss (USNHL) in children is often justified by the high likelihood of detecting abnormalities, which implies that these abnormalities are associated with hearing loss and that imaging has a positive contribution to patient outcome or well-being by providing information on the prognosis, hereditary factors, or cause of hearing loss.

OBJECTIVES

To evaluate the diagnostic yield of computed tomography (CT) and magnetic resonance imaging (MRI) in children with isolated unexplained USNHL and investigate the clinical relevance of these findings.

EVIDENCE REVIEW

Cochrane Library, Embase, PubMed, and Web of Science databases were searched for articles published from 1978 to 2017 on studies of children with USNHL who underwent CT and/or MRI of the temporal bone. Two authors (F.G.R. and E.N.B.P.) independently extracted information on population characteristics, imaging modality, and the prevalence of abnormalities and assessed the studies for risk of bias. Eligibility criteria included studies with 20 or more patients with USNHL who had CT and/or MRI scans, a population younger than 18 years, and those published in English.

MAIN OUTCOMES AND MEASURES

The pooled prevalence with 95% CI of inner ear abnormalities grouped according to finding and imaging modality.

FINDINGS

Of 1562 studies, 18 were included with a total of 1504 participants included in the analysis. Fifteen studies were consecutive case studies and 3 were retrospective cohort studies. The pooled diagnostic yield for pathophysiologic relevant findings in patients with unexplained USNHL was 37% for CT (95% CI, 25%-48%) and 35% for MRI (95% CI, 22%-49%). Cochleovestibular abnormalities were found with a pooled frequency of 19% for CT (95% CI, 14%-25%) and 16% for MRI (95% CI, 7%-25%). Cochlear nerve deficiency and associated cochlear aperture stenosis had a pooled frequency of 16% for MRI (95% CI, 3%-29%) and 44% for CT (95% CI, 36%-53%), respectively. Enlarged vestibular aqueduct (EVA) was detected with a pooled frequency of 7% for CT and 12% for MRI in children with USNHL.

CONCLUSIONS AND RELEVANCE

Imaging provided insight into the cause of hearing loss in a pooled frequency of about 35% to 37% in children with isolated unexplained USNHL. However, none of these findings had therapeutic consequences, and imaging provided information on prognosis and hereditary factors only in a small proportion of children, namely those with EVA. Thus, there is currently no convincing evidence supporting a strong recommendation for imaging in children who present with USNHL. The advantages of imaging should be carefully balanced against the drawbacks during shared decision making.

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

Objective

To summarize the high-resolution computed tomography (HRCT) and magnetic resonance imaging (HRMRI) features of duplicated internal auditory canals (DIACs).

Materials and Methods

Ear 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.

Results

The 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.

Conclusion

Double-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.

A Predictive Model for Cochlear Implant Outcome in Children with Cochlear Nerve Deficiency

The outcome of cochlear implantation (CI) in patients with cochlear nerve deficiency (CND) is variable, resulting in a wide range of speech perception performance, from degrees of environmental sound perception to conversation without lip-reading. Twenty-five cochlear implantees with CND were enrolled retrospectively to determine the factors correlated with CI outcome in patients with CND and to develop a predictive model for CI outcome. CI outcome was evaluated using the Categories of Auditory Performance (CAP) score at 2 years after CI. Patients with negative auditory brainstem response (ABR) showed a significantly lower CAP score than those with positive ABR (2.5 ± 1.7, 4.8 ± 0.7; p = 0.001). The area ratio of vestibulocochlear nerve (VCN) to facial nerve (FN) at the cerebellopontine angle on magnetic resonance images was positively correlated with CI outcome (p < 0.001). With multiple regression analysis, a predictive equation accounting for 66% of variance of CAP score at 2 years after CI was \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\bf{deduced}}:{\bf{CAP}}\,{\bf{score}}{\boldsymbol{=}}{\bf{0.7}}{\boldsymbol{+}}{\bf{1.9}}{\boldsymbol{\ast }}{\boldsymbol{(}}{\bf{ABR}}{\boldsymbol{)}}{\boldsymbol{+}}{\bf{1.2}}{\boldsymbol{\ast }}(\frac{{\boldsymbol{V}}{\boldsymbol{C}}{\boldsymbol{N}}}{{\boldsymbol{F}}{\boldsymbol{N}}})$$\end{document}deduced:CAPscore=0.7+1.9∗(ABR)+1.2∗(VCNFN). We found that preoperative ABR and area ratio of VCN to FN at the cerebellopontine angle could predict CI outcome in patients with CND. Preoperative counselling based on our predictive model might be helpful to determine treatment modality for auditory rehabilitation and which ear to implant.

Appropriate Imaging Modality for the Etiologic Diagnosis of Congenital Single-Sided Deafness in Children

We aimed to compare the diagnostic yield between temporal bone computed tomography (TBCT) and internal auditory canal MRI (IAC MRI) for the etiologic diagnosis of children with congenital single-sided deafness (SSD) and the evaluation of cochlear implant (CI) candidacy. In the original cohort, 24 subjects with congenital SSD were enrolled and underwent both TBCT and IAC MRI. We recruited an additional 22 consecutive infants with congenital SSD (the supplementary cohort) and evaluated in particular the cochlear nerve (CN) integrity using IAC MRI. Cochlear nerve deficiency (CND) was classified as ‘absent’, ‘small’, and ‘indeterminate’ via mutual comparison between optical and parameters based on the MRI results. The most common etiologies were CND in the original cohort (19 out of 24). Notably, accurate evaluations of CN status (‘small CN’ = 2, ‘indeterminate CN’ = 2), inner ear malformations, and brain abnormalities were possible only with MRI. The ‘indeterminate CN’ tended to be more frequently detected in SSD ears than in unaffected ears. MRI appeared to be more accurate than TBCT in a meticulous differentiation of CN, which is crucial for the selection of appropriate CI candidacy among congenital SSD children. Additionally, we introduced the novel concept of ‘indeterminate CN’, of which the causal relationship with SSD awaits confirmation.

Children with unilateral cochlear nerve canal stenosis have bilateral cochleovestibular anomalies

OBJECTIVES/HYPOTHESIS

To investigate the cochleovestibular apparatus bilaterally in children with isolated unilateral bony cochlear nerve canal (bCNC) stenosis.

STUDY DESIGN

Retrospective review.

METHODS

Imaging studies of children with unilateral bCNC stenosis (<1.0 mm) on computed tomography imaging (N = 36) were compared with controls imaged due to trauma without temporal bone injury (N = 32). Twenty-six measurements were obtained in each ear, assessing the bony internal auditory canal (IAC), cochlea, and vestibular end-organs, and were analyzed using one-way analysis of variance for intersubject comparisons and paired t tests for intrasubject comparisons with a Bonferroni adjustment for multiple comparisons (P = .0006).

RESULTS

Patients with bCNC stenosis had a smaller IAC (P < .000) and cochlea (P < .000) on the stenotic side as compared with controls. Although the vestibular end-organ was also smaller in bCNC ears, this difference was not significant. The contralateral ear also had a smaller bCNC (P < .000) and cochlea (P < .000) as compared with controls, although to a lesser degree than the stenotic side.

CONCLUSIONS

Children with unilateral bCNC stenosis have abnormal biometry of both the cochlea and the vestibular end-organ in the affected and the normal contralateral ear as compared with controls.

LEVEL OF EVIDENCE

3b Laryngoscope, 129:2403-2408, 2019.

Extremely common radiographic finding of cochlear nerve deficiency among infants with prelingual single-sided deafness and its clinical implications

OBJECTIVES

To clarify the common radiographic findings of audiologically documented prelingual single-sided deafness (SSD) and identify the prevalence of cochlear nerve deficiency (CND) in SSD infants referred from the newborn hearing screening program.

METHODS

Between March 2012 and March 2017, the records of all infants referred to our otology clinic after undergoing newborn hearing screening program were retrospectively reviewed. Twenty-four consecutive well infants without risk factors who had a confirmed diagnosis of prelingual SSD under the age of 1 year and who underwent internal auditory canal (IAC) magnetic resonance imaging (MRI) were included. The sizes of cochlear nerve (CN), IAC, and cochlear nerve canal (CNC) were measured on MRI. The presence of CND was visually determined by comparing the CN size to the ipsilateral facial nerve (FN) in the affected side via an oblique sagittal view of IAC MRI and defined when CN was absent or smaller than FN.

RESULTS

CND was seen in all 24 deaf ears (100%) on MRI. There was one with incomplete partition type I, and another with combined cochleovestibular nerve absence. Twenty-four subjects demonstrated either an absent (20/24, 83.3%) or small (4/24, 16.7%) CN. When the absent and small CN groups were compared, the former group had a higher prevalence of narrow CNC and narrow IAC. Of the 20 infants without identifiable CN on the affected side, 17 (85%) had narrow IAC and 17 (85%) had narrow CNC. In the 20 ears with absent CN, only one had both normal-sized IAC and CNC.

CONCLUSION

The contribution of CND to prelingual SSD in Korean infants reached 100%, according to IAC MRI alone.

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

OBJECTIVE

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.

SETTING

Tertiary pediatric referral center.

PATIENTS

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.

INTERVENTIONS

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.

MAIN OUTCOME MEASURE

Progression of hearing loss was defined by a 10 dB increase in air conduction pure-tone average.

RESULTS

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.

CONCLUSION

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.

Radiological Evaluation of Inner Ear with Computed Tomography in Patients with Unilateral Non-Pulsatile Tinnitus

OBJECTIVE

The objective of this research was to investigate the possible relationship between tinnitus and certain bony inner ear structures using computed tomography (CT).

MATERIALS AND METHODS

This was a prospective, controlled, double-blind study. The subjects of the study were divided into the following three groups: group 1 (G1), patients with unilateral sensorineural hearing loss (SNHL) and unilateral non-pulsatile tinnitus in the same ear; group 2 (G2), patients with normal hearing and unilateral non-pulsatile tinnitus; and group 3 (G3), healthy volunteers with neither tinnitus nor hearing loss. The basal turn length, internal acoustic canal (IAC) width and length, bony cochlear nerve canal (BCNC) width, and IAC diameter at the porus acousticus internus (PAI) were measured.

RESULTS

The mean BCNC width was significantly narrower in G1 and G2 than in the control group (G3) (p<0.001). For patients in G2, BCNC width was significantly narrower in ears with tinnitus (p<0.001) than in ears without tinnitus. The mean IAC diameter at PAI was also narrower in the G1 patients (p=0.007) compared with the other groups.

CONCLUSION

The results of this study suggest that CT evaluation of the inner ear structures is important in patients with tinnitus. According to the results, a narrow BCNC may cause phantom sensations and be related to cochlear nerve dysfunction. Therefore, it is recommended that clinicians evaluate BCNC carefully while assessing such patients.

CT Scan Imaging of the Human Fetal Labyrinth: Case Series Data Throughout Gestation

OBJECTIVES

The inner ear in humans reaches its final configuration and its adult size during fetal life. According to the literature, this occurs between 18 and 25 weeks of amenorrhea (WA). Our goal is to clarify the course of inner ear size development.

METHODS

Using computed tomography (CT) scanner, we studied 13 measurements in the inner ear of a collection of 153 fetuses from 21 to 40 WA.

RESULTS

We found no side-related differences or sexual dimorphism in the measurements. Cochlear and vestibular bone measurements did not show growth from 21 to 40 WA, with the exception of the lateral semicircular canal (LSCC) bony island, which grows until 25 WA. Internal auditory canal (IAC) and cochlear aqueduct (CA) growth are correlated with gestational age. As our cochlear measurements are similar to those of infants and adults, in accordance with the literature we conclude that the cochlea has reached its adult size before 21 WA. The continuous growth of the IAC and CA is linked to petrous ossification that continues during fetal gestation and after birth.

CONCLUSION

We confirm that the cochlea reaches its adult size during the second trimester of fetal life.

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

Objectives:

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.

Methods:

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.

Results:

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.

Conclusion:

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.

Audiologic and radiologic findings in cochlear hypoplasia

OBJECTIVE

The aim of the current study is to evaluate audiologic and radiologic findings of cochlear hypoplasia which is a subgroup of inner ear malformations.

METHODS

This study was a prospective clinical study and based on voluntary participation from cases with cochlear hypoplasia diagnosis. The study was conducted at Hacettepe University, Department of Otolaryngology, Head and Neck Surgery and Department of Audiology. Subjects were selected from an inner ear malformations database. Inclusion criteria were having cochlear hypoplasia for at least one ear. There were 66 subjects with an age range of 12 months and 60 years 5 months. For each subject, pure tone audiometry and tympanometry were applied according to chronological and cognitive age. And also, auditory brainstem response test was applied to when it is need. Subjects' radiologic results were reevaluated to confirm cochlear hypoplasia, cochlear nerve and cochlear aperture.

RESULTS

Cochlear hypoplasia types were statistically significantly different in terms of HL degree. This difference was caused by cochlear hypoplasia type IV group being was statistically different from the other three groups. Like with degree of HL, cochlear hypoplasia groups were statistically different from other three groups in terms of type of hearing loss. Cochlear aperture and cochlear nerve status showed variation according to cochlear hypoplasia type but these differences were not statistically approved.

CONCLUSIONS

In the current study, incidence of cochlear hypoplasia was 23.5% in all inner ear malformation. With this study, it was seen that subtypes of cochlear hypoplasia showed variability in terms of degree and type of hearing loss and also cochlear aperture and cochlear nerve status. Especially cochlear hypoplasia type IV differs from other three cochlear hypoplasia types.

Usefulness of radiological findings for predicting cochlear implantation outcomes in children with cochlear nerve deficiency: a pilot study

CONCLUSION

Children with CND received limited benefits from CIs and their results varied. The size of the vestibulocochlear nerve relative to the facial nerve could potentially be used as a predicator for CI outcomes in children with CND.

OBJECTIVE

This study aimed to (1) retrospectively review the outcomes of cochlear implants (CIs) in children with cochlear nerve deficiency (CND) and (2) evaluate the clinical usefulness of radiological findings as predictors for post-implantation outcomes.

METHODS

Study participants included 10 children with bilateral CND and profound sensorineural hearing loss. The preoperative magnetic resonance imaging and temporal bone computed tomography scans were evaluated. Auditory processing capability and speech perception performance were measured with Categories of Auditory Performance (CAP) and Speech Intelligibility Rating (SIR) scales. Aided hearing thresholds with CI were measured. The relationships between CI outcomes and the sizes of vestibulocochlear nerve and cochlear nerve canal (CNC) were analysed.

RESULTS

Although post-operative CAP scores and hearing thresholds significantly improved in children with CND, their results were worse than those measured in implanted children with normal cochlear nerve. No significant correlation was found between the CI outcomes and the vestibulocochlear nerve diameters or the CNC diameters in children with CND. However, children with larger vestibulocochlear-nerve-to-facial-nerve-ratios got better results.

Cochlear Implantation in Patients With CHARGE Syndrome

OBJECTIVE

To determine the optimal surgical approach for cochlear implantation (CI) preoperatively based on the spatial relation of a displaced facial nerve (FN) and middle ear structures and to analyze clinical outcomes of CHARGE syndrome.

METHODS

Facial nerve displacement and associated deviation of inner ear structures were analyzed in 13 patients (17 ears) with CHARGE syndrome who underwent CI. Surgical accessibility through the facial recess was assessed based on anatomical landmarks. Postoperative speech performance and associated clinical characteristics were analyzed.

RESULTS

The most consistently identified ear anomalies were semicircular canal aplasia (100%), ossicular anomaly (100%), and vestibular hypoplasia (88%). Facial nerve displacement was found in 77% of cases (anteroinferior: 47%, anterior: 24%, inferior: 6%). The width of available surgical space around facial recess was significantly greater in cases of facial recess approach (2.85 ± 0.9 mm) than those of alternative approach (0.12 ± 0.29 mm, P = .02). Postoperatively, 53% achieved better than category 4 on the categories of auditory perception (CAP) scale. The CAP category was significantly correlated with internal auditory canal diameter (P = .025) and did not differ according to the applied surgical approach.

CONCLUSION

Preoperative determination of surgical accessibility through facial recess would be useful for safe surgical approach, and successful hearing rehabilitation was achievable by applying appropriate surgical approaches.

Bony cochlear nerve canal stenosis and speech discrimination in pediatric unilateral hearing loss

OBJECTIVES/HYPOTHESIS

To examine the relationship between bony cochlear nerve canal (BCNC) width, degree of hearing loss, and speech discrimination in children with unilateral sensorineural hearing loss (USNHL).

STUDY DESIGN

Retrospective chart review (case-control study).

METHODS

Audiometric database was cross-referenced with radiologic database at pediatric tertiary care facility to identify children with USNHL and temporal bone computed tomography. BCNC widths were measured independently by two radiologists blinded to affected ear. Regression analyses investigated associations among variables.

RESULTS

One hundred and sixty children with USNHL had temporal bone imaging. Mean BCNC width was significantly smaller in affected ears, P = 0.0001. Narrower width was associated with more severe hearing loss, P = 0.01. Among children who had narrower cochlear nerve canals in affected ears compared to unaffected ears, smaller width was associated with lower speech discrimination score, P = 0.03. Increasing asymmetry in BCNC width between affected and unaffected ears was associated with poorer discrimination scores, P = 0.02. Among ears with asymmetrically smaller cochlear nerve canals, a 1-mm reduction in cochlear canal width between the normal and affected ear was associated with 30.4% lower word recognition score percentage in the affected ear, P = < 0.001.

CONCLUSION

There is a significant association between BCNC stenosis and impaired speech discrimination, independent of degree of hearing loss. Further investigation is needed to determine whether BCNC stenosis is a poor prognostic factor for auditory rehabilitation.

A New Classification of Cochleovestibular Malformations and Implications for Predicting Speech Perception Ability after Cochlear Implantation

Objectives: The aims of this study were to introduce a new classification of cochleovestibular malformation (CVM) and to investigate how well this classification can predict speech perception ability after cochlear implantation in children with CVM. Methods: Fifty-nine children with CVM who had used a cochlear implant for more than 3 years were included. CVM was classified into 4 subtypes based on the morphology of the cochlea and the modiolus on temporal bone computed tomography (TBCT): normal cochlea and normal modiolus (type A, n = 16), malformed cochlea and partial modiolus (type B, n = 31), malformed cochlea and no modiolus (type C, n = 6), and no cochlea and no modiolus (type D, n = 6). Speech perception test scores were compared between the subtypes of CVM using analysis of covariance with post hoc Bonferroni test. Univariate and multivariate regression analyses were used to identify the significant predictors of the speech perception test scores. Results: The speech perception test scores after implantation were significantly better in children with CVM type A or type B than in children with CVM type C or type D. The test scores did not differ significantly between the implanted children with CVM type A or type B and those without CVM. In univariate regression analysis, the type of CVM was a significant predictor of the speech perception test scores in implanted children with CVM. Multivariate regression analysis revealed that the age at cochlear implantation, cochlear nerve size and preimplantation speech perception test scores were significant predictors of the postimplantation speech perception test scores. The chance of cochlear nerve deficiency increased progressively from CVM type A to type D. Conclusion: The new classification of CVM based on the morphology of the cochlea and the modiolus is simple and easy to use, and correlated well with postimplantation speech perception ability and cochlear nerve status. This simple classification of CVM using TBCT with cochlear nerve assessment by magnetic resonance imaging is helpful in the preoperative evaluation of children with CVM.

Detection of hypoplasia of bony cochlear nerve canal by the opening threshold of virtual endoscopy: a pilot study

BACKGROUND

Dimensions of the bony cochlear nerve canal (BCNC) have been proposed as a potential diagnostic standard for BCNC hypoplasia, but the standard remains inconsistent. Some studies have revealed that computed tomography virtual endoscopy (CTVE) with variation of reconstruction threshold is good at identifying labyrinthine fistulas or semi-circular canal dehiscence.

PURPOSE

To examine diagnostic accuracy of VE in the evaluation of BCNC hypoplasia on basis of opening threshold.

MATERIAL AND METHODS

Twenty ears diagnosed with BCNC hypoplasia were included in this study. One hundred ears served as controls. The opening thresholds were measured by two reviewers. Intraclass correlation coefficients (ICC) were reported. The width of BCNC was obtained on transverse CT images. Association between the width of BCNC and opening threshold was assessed by using Spearman correlation coefficients. ROC curves were applied to assess the best cut-off value of opening threshold.

RESULTS

The opening threshold of BCNC was significantly higher in diseased ears (926 ± 308 Hounsfield units [HU]) than that in control ears (287 ± 72 HU). Inter-observer agreement was very good. The mean width of BCNC for diseased ears and control ears were 0.83 ± 0.36 mm and 2.21 ± 0.35 mm, respectively. Significant negative linear correlation was found between opening thresholds and width of BCNC (Spearman coefficient, -0.768; P < 0.001). The area under the ROC curve was 0.981. The cut-off opening thresholds of 408 for differentiation between the two groups provided the best combination of sensitivity (85%) and specificity (94%).

CONCLUSION

The VE with opening threshold may be an effective optional tool for prediction of hypoplasia of BCNC.

Restudy of malformations of the internal auditory meatus, cochlear nerve canal and cochlear nerve

The present study aims to restudy the correlation between the internal auditory meatus (IAM), the cochlear nerve canal (CNC), the cochlear nerve (CN) and inner ear malformations. In this retrospective study design, the abnormal diameter of the IAM, CNC and CN in patients with any kind of inner ear malformations was evaluated using multi-slice spiral computed tomography (MSCT) (37 patients) and magnetic resonance imaging (MRI) (18 patients). Of 37 MSCT-diagnosed patients, 2 had IAM atresia, 11 IAM stenosis, 22 enlarged IAM, and 2 normal IAM with an abnormal CN. MRI diagnoses of 18 patients revealed 8 cases of aplastic CN, 6 hypoplastic CN, and 4 normal CN. CNC stenosis was associated with CN hypoplasia (P < 0.001). Patients with absent or stenotic IAM had less CN development than those with normal or enlarged IAM (P = 0.001). We propose a modification of the existing classification systems with a view to distinguishing malformations of the IAM, CNC and CN.

Auditory neuropathy spectrum disorder: predictive value of radiologic studies and electrophysiologic tests on cochlear implant outcomes and its radiologic classification

CONCLUSION

The width of the bony cochlear nerve canal (BCNC) and the size of the cochlear nerve are reliable predictors of long-term speech perception abilities for children with auditory neuropathy spectrum disorder (ANSD) after cochlear implantation (CI). In addition, electrical stapedial reflex (ESR) and electrical compound action potential (ECAP) also have considerable value in predicting postoperative speech perception abilities in these children.

OBJECTIVES

To assess whether speech perception abilities after CI in children with ANSD can be predicted from the results of radiologic studies and electrophysiologic tests.

METHODS

Fifteen children with ANSD underwent CI. The width of the BCNC and the size of the cochlear nerve were measured using preoperative CT and MRI. The results of early postoperative ESR, ECAP, and implant evoked electrical auditory brainstem response were reviewed. The latest speech perception test scores were also reviewed.

RESULTS

Radiologic findings of normal BCNC and normal cochlear nerve correlated with excellent speech perception abilities after CI. A narrow or obliterated BCNC and a deficient cochlear nerve correlated with poor speech perception abilities. Children with good speech perception abilities showed robust responses on ESR and ECAP, but there were no responses from any of the children with poor speech perception abilities.

The cochlear nerve canal and internal auditory canal in children with normal cochlea but cochlear nerve deficiency

BACKGROUND

There is an increasing frequency of requests for cochlear implantation (CI) in deaf children and more detailed image information is necessary for selecting appropriate candidates. Cochlear nerve deficiency (CND) is a contraindication to CI. Magnetic resonance imaging (MRI) has been used to evaluate the integrity of the cochlear nerve. The abnormalities of the cochlear nerve canal (CNC) and internal auditory canal (IAC) have been reported to be associated with CND.

PURPOSE

To correlate CNC manifestation, size, and IAC diameter on high-resolution CT (HRCT) with CND diagnosed by MRI in children.

MATERIAL AND METHODS

HRCT images from 35 sensorineurally deaf children who had normal cochlea but bilateral or unilateral CND diagnosed by MRI were studied retrospectively. The CNC and IAC manifestation and size were assessed and correlated with CND.

RESULTS

CND was diagnosed by MRI in 54/70 ears (77.1%). Thirty-two ears had an absent cochlear nerve (59.3%), while 22 ears had a small cochlear nerve (40.7%). The CNC diameter was <1.5 mm in 36 ears (66.7%). The CNC diameter ranged between 1.5 and 2.0 mm in seven ears (13.0%) and was >2.0 mm in 11 ears (20.4%). The IAC diameter was <3.0 mm in 25 ears (46.3%) and >3.0 mm in 29 ears (53.7%).

CONCLUSION

The hypoplastic CNC might be more highly indicative of CND than that of a narrow IAC.

Proportion of bony cochlear nerve canal anomalies in unilateral sensorineural hearing loss in children

OBJECTIVE

The aim of this study was to characterize the various bony anomalies of the inner ear in patients with unilateral sensorineural hearing loss using high-resolution temporal bone computed tomography and establish the relationship between hearing and the diameter of the bony cochlear nerve canal.

METHODS

We performed a retrospective review of 51 patients (mean age 11 years, range 0-20 years, 27 boys, 24 girls) who were diagnosed with unilateral sensorineural hearing loss with an audiogram. Coronal and axial diameter of the inner ear structures, including the internal auditory canal, bony cochlear nerve canal, and each turn of the cochlea and semicircular canals, were measured with high-resolution temporal bone computed tomography. The mean values (± 2 standard deviations) were calculated and compared between sensorineural hearing loss and normal ears, and between narrow bony cochlear nerve canal and normal bony cochlear nerve canal ears. Bony cochlear nerve canal atresia/stenosis was defined as a value less than 1.4mm in axial images.

RESULTS

The diameter of the bony cochlear nerve canal was significantly smaller in sensorineural hearing loss ears than in normal ears (p<.05). Associated inner ear anomalies, such as IAC stenosis (24%), cochlear hypoplasia (7-17%), and narrow semicircular canal bony island (8%) were only observed in the narrow bony cochlear nerve canal group. This group also showed statistically significant, severe to profound hearing loss compared to the normal bony cochlear nerve canal group (p<.05, R(2)=12.8%).

CONCLUSIONS

Most (57%) of the unilateral sensorineural hearing loss ears had bony cochlear nerve canal stenosis/atresia and this group showed associated inner ear anomalies. When the diameter of the bony cochlear nerve canal was less than 1.4mm, pure tone audio averages were more than 70 dB HL in most ears.

High prevalence of inner-ear and/or internal auditory canal malformations in children with unilateral sensorineural hearing loss

OBJECTIVE

Radiological and genetic examination has recently advanced for diagnosis of congenital hearing loss. The aim of this study was to elucidate the prevalence of inner-ear and/or internal auditory canal malformations in children with unilateral sensorineural hearing loss (USNHL) for better management of hearing loss and genetic and lifestyle counseling.

METHODS

We conducted a retrospective study of charts and temporal bone computed tomography (CT) findings of 69 consecutive patients 0-15 years old with USNHL. In two cases, genetic examination was conducted.

RESULTS

Of these patients, 66.7% had inner-ear and/or internal auditory canal malformations. The prevalence of malformations in infants (age <1 year) was 84.6%, which was significantly higher than that in children 1-15 years old (55.8%; p<0.01). Almost half of the patients (32; 46.4%) had cochlear nerve canal stenosis; 13 of them had cochlear nerve canal stenosis alone, and in 19 it accompanied other malformations. Internal auditory canal malformations were observed in 22 subjects (31.8%), 14 (20.3%) had cochlear malformations, and 5 (7.2%) had vestibular/semicircular canal malformations. These anomalies were seen only in the affected ear, except in two of five patients with vestibular and/or semicircular canal malformations. Two patients (2.9%) had bilateral enlarged vestibular aqueducts. Mutations were found in SLC26A4 in one of the two patients with bilateral large vestibular aqueducts. The prevalence of a narrow internal auditory canal was significantly higher in subjects with cochlear nerve canal stenosis (50.0%) than in subjects with normal cochlear nerve canals (11.1%; p<0.01). There were no correlations between the type and number of malformations and hearing level.

CONCLUSIONS

The prevalence of inner-ear and/or internal auditory canal malformations detected by high-resolution temporal bone CT in children with USNHL was very high. Radiological and genetic examination provided important information to consider the pathogenesis and management of hearing loss. Temporal bone CT should be recommended to children with USNHL early in life. SLC26A4 mutation also should be examined in cases with bilateral enlarged vestibular aqueduct.

A case with the bilateral narrow bony cochlear nerve canals associated with near normal hearing thresholds

The narrow bony cochlear nerve canal in high resolution temporal bone computed tomography is frequently found in patients of congenital sensorineural hearing loss. But this bony structural anomaly could not conclude the functional outcome of cochlear nerve. Here, we present a case of a 14-month-old girl having bilateral narrow bony cochlear nerve canals. In magnetic resonance imaging, both the cochlear nerves were identified to be intact. Moreover, acoustic brainstem response threshold and auditory steady state response revealed nearly normal hearing thresholds. Therefore, we suggest that the narrow bony cochlear nerve canal itself does not necessarily indicate a substantial degree of hearing loss.

Pediatric cochlear implantation of children with eighth nerve deficiency

OBJECTIVE

To evaluate the auditory outcomes of children implanted in an ear with eighth nerve hypoplasia or aplasia and to determine whether preoperative characteristics are predictive of auditory performance achieved.

STUDY DESIGN

retrospective case review.

SETTING

tertiary care medical center.

PATIENTS

ten children implanted in an ear with eighth nerve hypoplasia or aplasia, as determined by high resolution magnetic resonance imaging.

MAIN OUTCOME MEASURES

Neural response test measurements, detection and speech awareness thresholds, Meaningful Auditory Integration Scale scores, as well as speech perception level achieved.

RESULTS

Post-implantation, three children demonstrated little to no detection of sound, three had improved detection and awareness of environmental sounds, one developed closed-set speech perception and spoken language, and three developed open-set speech perception and spoken language. No imaging findings appeared related to outcomes. Significantly better implant detection thresholds and Meaningful Auditory Integration Scale scores were found in children who had preoperative aided auditory detection (p's ≤ 0.02-0.05).

CONCLUSION

Some children with eighth nerve hypoplasia or aplasia may derive significant benefit from a cochlear implant. In our study high resolution magnetic resonance imaging was more sensitive than high resolution computer tomography in detecting neural deficiency. However, no imaging findings were predictive of auditory performance level achieved post-implantation.

Implication of bony cochlear nerve canal on hearing in patients with congenital unilateral sensorineural hearing loss

This study was designed to evaluate the dimensions of the bony cochlear nerve canal (BCNC) in congenital unilateral sensorineural hearing loss (USNHL) patients with normal inner ears, and to analyze the correlation between BCNC and hearing status. Medical records and temporal bone computed tomography (TBCT) findings of 380 patients who visited Seoul National University Hospital between January 1999 and December 2007 were reviewed retrospectively. The length and width of the BCNC at the fundus of the internal auditory canal were measured in millimeters based on the axial view of TBCT for three ear groups: normal inner ears of control group subjects (group A, 179 ears), normal inner ears on the contralateral side of USNHL patients (group B, 201 ears), and the affected inner ears in USNHL (group C, 201 ears). The mean values of length and width in group C (0.79 ± 0.36 and 1.58 ± 0.83 mm, respectively) were significantly smaller than those in group A (1.07 ± 0.10 and 2.38 ± 0.28 mm, respectively; p < 0.001) and group B (1.04 ± 0.23 and 2.33 ± 0.39 mm, respectively; p < 0.001). The receiver operating characteristic curves for BCNC were conducted to estimate the cutoff values from which the proportions of profound hearing loss increased, compared to those of mild to severe hearing loss. The areas under the curve were 0.487 ± 0.044 (p = 0.781) and 0.622 ± 0.041 (p = 0.011) for length and width, respectively. The cutoff value of width with a sensitivity of 90% for profound USNHL was 1.16 mm in otherwise normal inner ears. Clinicians would be recommended to take a close look at BCNC as one of the possible causes of hearing loss in otherwise normal inner ears of USNHL on TBCT.

Cochlear implantation in children with cochlear nerve absence or deficiency

OBJECTIVE

To evaluate speech perception after cochlear implantation in children with cochlear nerve absence or deficiency.

METHODS

A retrospective case review was performed to identify children who underwent cochlear implantation with cochlear nerve absence or deficiency. The cochlear nerve was evaluated by high-resolution three-dimensional T2-weighted fast spin echo MR in the oblique sagittal and axial planes. A deficient cochlear nerve was defined as a cochlear nerve that is smaller in diameter when compared with the adjacent facial nerve in the midportion of the internal auditory canal. The cochlear nerve was considered absent if there was no imaging evidence of a cochlear nerve. Speech awareness threshold and the speech perception category score were used to measure speech perception after cochlear implantation.

RESULTS

Seven children who underwent cochlear implantation in an ear without imaging evidence of a cochlear nerve were identified. One child developed early closed-set speech recognition. The other 6 children developed only speech detection or pattern perception. Two children underwent cochlear implantation with a deficient cochlear nerve. One developed consistent closed-set word recognition and the other developed early closed-set word recognition. The mean follow-up time for all patients was 3.8 years (range, 1.1-7.1 yr).

CONCLUSION

Cochlear nerve deficiency is not an uncommon cause for profound sensorineural hearing loss and presents a challenge in the decision-making process regarding whether to proceed with a cochlear implant. Children with a deficient but visible cochlear nerve on magnetic resonance image can expect to show some speech understanding after cochlear implantation; however, these children do not develop speech understanding to the level of implanted children with normal cochlear nerves. Children with an absent cochlear nerve determined by magnetic resonance imaging can be expected to have limited postimplantation sound and speech awareness.

The cochleovestibular nerve identified during auditory brainstem implantation in patients with narrow internal auditory canals: can preoperative evaluation predict cochleovestibular nerve deficiency?

OBJECTIVES/HYPOTHESIS

To analyze the value of preoperative diagnostic tools in predicting the status of the cochleovestibular nerve (CVN) in patients with narrow internal auditory canals (IAC).

STUDY DESIGN

Retrospective case series at a tertiary hospital.

METHODS

Eight profoundly deaf patients with narrow IACs who received auditory brainstem implantation were included in this study. The results of preoperative imaging, electrophysiologic, and auditory tests were correlated with the CVN status identified during auditory brainstem implantation.

RESULTS

Temporal bone computed tomography (CT) findings, including the patency of the bony cochlear nerve canal and the diameter of the IAC, were limited in accurately reflecting the status of the CVN. Magnetic resonance imaging (MRI) and preoperative auditory responses to either pure tone or environmental sounds were more accurate markers for detecting the presence of a CVN than CT; however, there were limitations in cases with a very thin CVN or combined severe mental retardation. Absence of promontory or intracochlear electrically evoked auditory brainstem responses were not always indicative of an absent CVN.

CONCLUSIONS

Visualization on MRI and detection of auditory responses suggested the presence of a CVN in patients with narrow IACs; however, the possibility of the presence of a CVN should be considered even when there is no clear evidence of a CVN on preoperative evaluations. Therefore, physicians should be prudent when determining candidacy for cochlear implantation or auditory brainstem implantation in patients with narrow IACs.