A Study of Outcome of Pediatric Cochlear Implantation in Patients with Cochleovestibular Nerve Deficiency.

OBJECTIVES: A cochleovestibular nerve deficiency (CVND) could compromise stimulation of nerve by electrical pulses delivered from a cochlear implant, thereby hindering activity along auditory pathway. The evaluation of children with congenital hearing loss with a high-resolution magnetic resonance imaging is presently the investigative modality of choice to diagnose CVND. The aim of this study was to determine the outcomes in pediatric cochlear implant recipients with a diagnosis of CVND. The objectives included (1) to study the prevalence of CVND among children with prelingual congenital severe to profound hearing loss; (2) to assess post cochlear implantation (CI) outcomes in children with CVND using categories of auditory performance (CAP), speech intelligibility rating (SIR), and cortical auditory evoked potentials (CAEPs); and (3) to propose a management protocol for these children. MATERIALS AND METHODS: All CI procedures performed during the study period in children 5 years or younger were included in study. All patients who were older than 5 years or had syndromic associations, multiple disabilities, second side or revision CI were excluded from the study. Children with unilateral cochleovestibular nerve aplasia and all other cases of CVND (type IIa and IIb) were advised to undergo CI on side with more radiologically robust nerve and/or cochlea anatomy. Children with bilateral CVND were included in group A, and age-matched cochlear implant candidates with normal cochleovestibular nerve anatomy were included in group B for statistical comparison of outcomes. RESULTS: In group A, post CI CAP and SIR, CAEP amplitude and latency at 12 months showed statistically significant difference (p<0.05) compared with preoperative values. However, mean score of CAEP latency and amplitude and SIR score was worse for group A compared with group B at 12 months, which was statistically significant (p<0.05). CONCLUSION: This study supports the fact that CI is a viable option to be offered in children with CVND (type IIa and IIb) for the development of auditory perception and speech.

A de novo SIX1 variant in a patient with a rare nonsyndromic cochleovestibular nerve abnormality, cochlear hypoplasia, and bilateral sensorineural hearing loss.

BACKGROUND: Childhood hearing impairment affects language and cognitive development. Profound congenital sensorineural hearing impairment can be due to an abnormal cochleovestibular nerve (CVN) and cochleovestibular malformations, however, the etiology of these conditions remains unclear. METHODS: We used a trio-based exome sequencing approach to unravel the underlying molecular etiology of a child with a rare nonsyndromic CVN abnormality and cochlear hypoplasia. Clinical and imaging data were also reviewed. RESULTS: We identified a de novo missense variant [p(Asn174Tyr)] in the DNA-binding Homeodomain of SIX1, a gene which previously has been associated with autosomal dominant hearing loss (ADHL) and branchio-oto-renal or Branchio-otic syndrome, a condition not seen in this patient. CONCLUSIONS: SIX1 has an important function in otic vesicle patterning during embryogenesis, and mice show several abnormalities to their inner ear including loss of inner ear innervation. Previous reports on patients with SIX1 variants lack imaging data and nonsyndromic AD cases were reported to have no inner ear malformations. In conclusion, we show that a de novo variant in SIX1 in a patient with sensorineural hearing loss leads to cochleovestibular malformations and abnormalities of the CVN, without any other abnormalities. Without proper interventions, severe to profound hearing loss is devastating to both education and social integration. Choosing the correct intervention can be challenging and a molecular diagnosis may adjust intervention and improve outcomes, especially for rare cases.

Axial Mesodermal Dysplasia Complex with a Unique Abnormal Course of Vestibulocochlear Nerve.

Axial mesodermal dysplasia complex (AMDC) is a combination of multiple congenital malformations arising due to the mesodermal cell migration, neural tube fusion, and rhombencephalon segmentation. Here, we present the imaging findings of a 15-year-old boy with AMDC who has bilateral inner ear malformations associated with a vestibulocochlear nerve extending to Meckel cave, cystic lesion in prepontine cisterna, cervical vertebral segmentation anomalies, and maxillar bone anomalies.

Abnormal Cochleovestibular Anatomy and Hearing Outcomes: Pediatric Patients with a Questionable Cochleovestibular Nerve Status May Benefit from Cochlear Implantation and/or Hearing Aids.

OBJECTIVE: Imaging characteristics and hearing outcomes in children with cochleovestibular or cochleovestibular nerve (CVN) abnormalities. STUDY DESIGN: Retrospective, critical review. SETTING: Tertiary referral academic center. PATIENTS: Twenty-seven children with CVN abnormalities with magnetic resonance (MRI) and/or computed tomography (CT). Study Intervention(s): None. MAIN OUTCOME MEASURE(S): Determine the likely presence or absence of a CNV and auditory stimulation responses. RESULTS: Two of 27 cases had unilateral hearing loss, and all others had bilateral loss. Eleven (46%) were identified with a disability or additional condition. Twenty-two (42%) ears received a cochlear implant (CI) and 9 ears (17%) experienced no apparent benefit from the device. MRI acquisition protocols were suboptimal for identification of the nerve in 22 (42%) ears. A likely CVN absence was associated with a narrow cochlear aperture and internal auditory canal and cochlear malformation. Thirteen (48%) children with an abnormal nerve exhibited normal cochleae on the same side. Hearing data were available for 30 ears, and 25 ears (83%) exhibited hearing with or without an assistive device. One child achieved closed set speech recognition with a hearing aid, another with a CI. One child achieved open set speech recognition with a CI. CONCLUSIONS: Current imaging cannot accurately characterize the functional status of the CVN or predict an assistive device benefit. Children who would have otherwise been denied a CI exhibited auditory responses after implantation. A CI should be considered in children with abnormal CVN. Furthermore, imaging acquisition protocols need standardization for clear temporal bone imaging.

Auditory Brainstem Implant Array Position Varies Widely Among Adult and Pediatric Patients and Is Associated With Perception.

OBJECTIVES: The auditory brainstem implant (ABI) provides sound awareness to patients who are ineligible for cochlear implantation. Auditory performance varies widely among similar ABI cohorts. We hypothesize that differences in electrode array position contribute to this variance. Herein, we classify ABI array position based on postoperative imaging and investigate the relationship between position and perception. DESIGN: Retrospective review of pediatric and adult ABI users with postoperative computed tomography. To standardize views across subjects, true axial reformatted series of scans were created using the McRae line. Using multiplanar reconstructions, basion and electrode array tip coordinates and array angles from vertical were measured. From a lateral view, array angles (V) were classified into types I to IV, and from posterior view, array angles (T) were classified into types A to D. Array position was further categorized by measuring distance vertical from basion (D1) and lateral from midline (D2). Differences between array classifications were compared with audiometric thresholds, number of active electrodes, and pitch ranking. RESULTS: Pediatric (n = 4, 2 with revisions) and adult (n = 7) ABI subjects were included in this study. Subjects had a wide variety of ABI array angles, but most were aimed superiorly and posteriorly (type II, n = 7) from lateral view and upright or medially tilted from posterior view (type A, n = 6). Mean pediatric distances were 8 to 42% smaller than adults for D1 and D2. In subjects with perceptual data, electrical thresholds and the number of active electrodes differed among classification types. CONCLUSIONS: In this first study to classify ABI electrode array orientation, array position varied widely. This variability may explain differences in auditory performance.

Bilateral microtia, canal atresia and aplasia of cochleovestibular nerve.

A six-month-old baby with congenital patent ductus arteriosus (PDA), bilateral microtia and canal atresia was referred for hearing assessment. The audiology assessment revealed bilateral profound hearing loss, which is atypical for a case of pure canal atresia. Imaging was performed much earlier than usual and, as suspected, the patient also had bilateral severe inner ear anomaly. It is extremely rare for a person to have both external and inner ear anomaly because of the different embryological origin. The only suitable hearing rehabilitation option for this kind of patients is brainstem implant. However, the parents had opted for sign language as a form of communication.

The relationship between the dimensions of the internal auditory canal and the anomalies of the vestibulocochlear nerve.

BACKGROUND: Internal auditory canal (IAC) stenosis and vestibulocochlear nerve (VCN) abnormalities have been reported to be associated with sensorineural hearing loss. Previous studies classified the normal dimensions of the IAC and its anomalies with no consideration of the VCN. Other studies categorised the VCN development in only stenotic canals. In the present study, an anatomical classification of the normal dimensions of the IAC and its anomalies and their association with malformations of the VCN and its subdivisions were described. MATERIALS AND METHODS: Retrospective review was undertaken for children ranged from 1 to 10 years. A total of 764 canals were investigated for pre-operative assessment of cochlear implantation. Other 100 canals of normal hearing ears were included as the control group. The maximum anteroposterior diameter, considered the width of the canal, was measured in axial plane and the length of the canal was identified in coronal plane. The canals were categorised normal: if they are from 3 to 8 mm, patulous: if they are more than 8 mm, stenotic: if they are less than 3 mm and atretic if absent, using multislice computed tomography. The VCN trunks and their subdivisions were investigated using magnetic resonance imaging. RESULTS: Internal auditory canals were found normal in 66% with a mean width: 5.27 ± ± 0.68, patulous in 17% with a mean width 113% more than that of the control group (p = 0.000), stenotic in 13% with a mean width 73% less as compared to that of the control group (p = 0.000) and atretic in 4% of the experimental canals. The VCN trunks were found normal with well-developed subdivisions in 77.8% of the normal canals, 98.4% of the patulous canals, and 19.2% of the stenotic canals. The VCN trunks were normal with hypoplastic subdivisions in 11.3% of the normal canals, 1.6% in the patulous canals, and 61.6% in the stenotic canals with a mean width 52% less than that of the normal trunk with developed subdivisions. Hypoplastic VCN trunks with absent subdivisions were reported in 7.3% of the normal canals, 11.1% of the stenotic canals and in 3.2% of the atretic canals. The VCN trunks were not found in 3.6% of the normal canals, in 8.1% of the stenotic canals and in 96.8% of the atretic canals. CONCLUSIONS: Internal auditory canal formation was dependent on the process of development and growth of the eighth cranial nerve and its subdivisions that greatly affected the completion of IAC canalisation. This paper could serve as a reference providing a quantitative classification of the relationship between the dimensions of the IAC and the development of the VCN trunk and its subdivisions.

Malformation of the eighth cranial nerve in children. / Malformaciones del octavo par en niños.

INTRODUCTION AND OBJECTIVES: Prevalence of congenital sensorineural hearing loss (SNHL) is approximately 1.5-6 in every 1,000 newborns. Dysfunction of the auditory nerve (auditory neuropathy) may be involved in up to 1%-10% of cases; hearing losses because of vestibulocochlear nerve (VCN) aplasia are less frequent. The objectives of this study were to describe clinical manifestations, hearing thresholds and aetiology of children with SNHL and VCN aplasia. METHODOLOGY: We present 34 children (mean age 20 months) with auditory nerve malformation and profound HL taken from a sample of 385 children implanted in a 10-year period. We studied demographic characteristics, hearing, genetics, risk factors and associated malformations (Casselman's and Sennaroglu's classifications). Data were processed using a bivariate descriptive statistical analysis (P<.05). RESULTS: Of all the cases, 58.8% were bilateral (IIa/IIa and I/I were the most common). Of the unilateral cases, IIb was the most frequent. Auditory screening showed a sensitivity of 77.4%. A relationship among bilateral cases and systemic pathology was observed. We found a statistically significant difference when comparing hearing loss impairment and patients with different types of aplasia as defined by Casselman's classification. Computed tomography (CT) scan yielded a sensitivity of 46.3% and a specificity of 85.7%. However, magnetic resonance imaging (MRI) was the most sensitive imaging test. CONCLUSIONS: Ten percent of the children in a cochlear implant study had aplasia or hypoplasia of the auditory nerve. The degree of auditory loss was directly related to the different types of aplasia (Casselman's classification) Although CT scan and MRI are complementary, the MRI is the test of choice for detecting auditory nerve malformation.

Pontine Tegmental Cap Dysplasia: MR Evaluation of Vestibulocochlear Neuropathy.

Pontine tegmental cap dysplasia (PTCD) is recently recognized as a rare congenital brain stem malformation with typical neuroimaging hallmarks of ventral pontine hypoplasia and vaulted pontine tegmentum projecting into the fourth ventricle. PTCD patients also demonstrate variable cranial neuropathy with predilection for involvement of the vestibulocochlear and facial nerves. We present a case of PTCD diagnosed on MRI in the neonatal period. During early infancy, the patient displayed features of multiple cranial neuropathies and bilateral hearing loss. At the age of 2, the patient underwent further MRI assessment with dedicated high resolution T2 SPACE sequence to delineate the cranial nerve deficiencies.

Agenesia aislada del VIII par de diagnóstico tardío / Late diagnosis of isolated agenesis of cranial nerve VIII

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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.

Duplicate internal auditory canals with facial and vestibulocochlear nerve dysfunction.

OBJECTIVE: We report an extremely rare case of duplication of the internal auditory canal associated with dysfunction of both the facial and vestibulocochlear nerves. We also review the literature regarding the integrity of the facial and vestibulocochlear nerves in such cases. CASE REPORT: A 34-year-old man presented with unilateral, right-sided, sensorineural hearing loss and facial nerve palsy since childhood. Facial nerve function was observed to be House-Brackmann grade III. Computed tomography and magnetic resonance imaging demonstrated ipsilateral duplicate, vacant internal auditory canals. Based on the clinical presentation, we interpreted these radiological findings as aplasia of the vestibulocochlear nerve and severe hypoplasia of the facial nerve. CONCLUSION: To our best knowledge, this is the first report of vestibulocochlear nerve aplasia and severe facial nerve hypoplasia in a case of ipsilateral duplication of the internal auditory canal. High resolution gradient echo magnetic resonance imaging sequences are advocated for assessment of neural integrity in patients with an abnormal internal auditory canal and facial and/or vestibulocochlear nerve dysfunction.

The vestibulocochlear nerve: aplasia and hypoplasia in combination with inner ear malformations.

OBJECTIVE: To determine features of hypoplasia and aplasia of the vestibulocochlear nerve (VCN) in combination with inner ear malformations (IEMs). METHODS: Index cases were retrospectively selected from all IEMs collected since 1995. CT and MRI data were reviewed by two neuroradiologists. The number and thickness of visible nerves in the cerebellopontine angle cistern and inside the internal auditory canal (IAC) were analysed. RESULTS: MR images for 176 patients with IEMs were analysed. Labyrinthine aplasia and otocyst deformity showed 100% correlation, and IAC malformations exhibited 92% correlation with VCN aplasia. Cochlear aplasia, complete aplasia of the semicircular canals, severe cochlear hypoplasia, common cavity, incomplete partition type 1 and mild cochlear hypoplasia showed decreasing degrees of correlation with hypoplasia of the VCN. The remaining types of IEM did not demonstrate VCN hypoplasia. CONCLUSIONS: Certain forms of IEM show 100% correlation with hypoplasia or aplasia of the VCN, while others correlate less strongly and some do not usually exhibit VCN hypoplasia. MRI should always be carried out for those forms often correlated with VCN hypoplasia. KEY POINTS: Vestibulocochlear nerve deficiency can be strongly suspected in certain inner ear malformations • Bony cochlear aplasia and cochlear nerve aplasia are strongly correlated • In semicircular canal aplasia, hypoplasia of the vestibular nerve can be found • Before cochlear implantation, the type of any IEM should be fully understood.

[Evaluation with functional magnetic resonance imaging in 1 case of cochleovestibular nerve malformation in children before cochlear implantation and review of the literature].

OBJECTIVE: To evaluate the feasibility of cochlear implantation by functional magnetic resonance imaging (fMRI) in a patient with cochleovestibular nerve hypoplasia. METHOD: Audiometry, radiological examination and fMRI of the auditory cortex were performed to a 15-year-old boy with bilateral hearing loss before cochlear implantation. RESULT: Results of pure tone audiometry and auditory brainstem responses showed profound sensorineural hearing loss (SNHL). Transiently evoked otoacoustic emission was absent on both sides. High resolution computed tomography revealed the inner ear malformation (incomplete partition I) on both side. Oblique sagittal reconstruction in magnetic resonance imaging (MRI) showed the malformation of cochleovestibular nerve, fMRI demonstrated the activation of the right primary auditory cortex during 1-kHz monaural stimulation on the left side. No cortical activation appeared during the monaural right acoustic stimulation using the same sound pressure level. The child had subjective auditory response 1 month after cochlear implantation on his left side. CONCLUSION: fMRI would be an effective measure in the assessments for the cochlear implantation candidates, combining with audiometry and radiological examination, especially when MRI shows cochleovestibular nerve malformation in these patients.

Bilateral narrow duplication of the internal auditory canal.

AIM: To demonstrate diagnostic imaging of an extremely rare presentation of bilateral narrow duplication of the internal auditory canal. CASE REPORT: An adolescent boy with profound sensorineural hearing loss presented for hearing rehabilitation. Imaging studies (i.e. multidetector computed tomography and magnetic resonance imaging) clearly demonstrated bilateral duplication of the internal auditory canals, with narrowing of the lower canals, unilateral cochlear and vestibular dysplasia, bilateral superior semicircular canal malformation, and bilateral absence of the posterior semicircular canals. CONCLUSION: To our knowledge, this is only the third such case described in the literature. Considering that the vestibulocochlear nerve has been unable to be demonstrated in almost all cases of duplicated internal auditory canal (unilateral and bilateral), our case supports the hypothesis that vestibulocochlear nerve aplasia or hypoplasia leads to internal auditory canal stenosis. We consider this rare presentation of bilateral narrow duplication of the internal auditory canal to represent a contraindication for cochlear implantation.

Bilateral implantation in children with cochleovestibular nerve hypoplasia.

To report on the outcomes of sequential bilateral cochlear implantation (CI) in children with inner ear malformation. The study design is a retrospective case study. The setting is a tertiary reference center. Two children presenting a profound bilateral congenital hearing loss with bilateral hypoplasia of the cochleovestibular nerves and hypoplasic external semicircular canal had a cochlear implant at respectively 16 months and 33 months. A second implant was proposed at respectively 17 and 20 months after the first implant. The main outcome measures are audiometry, perceptive results in closed and open set words (CSW and OSW) and oral production at follow-up. The first cochlear implant gave respectively mean thresholds at 60 dB and 70 dB. Bilateral CI showed mean threshold at respectively 40 dB and 55 dB. In case 1, perceptive assessment was 83% and 70% in respectively CSW and OSW with oral production and comprehension of sentences after 1 year follow-up. In case 2, the perceptive assessment showed no perceptive or linguistic evolution at 6 months follow-up. In cochleovestibular nerve hypoplasia, bilateral implantation could be discussed in cases of limited result after unilateral implant.

Narrow duplicated or triplicated internal auditory canal (3 cases and review of literature): can we regard the separated narrow internal auditory canal as the presence of vestibulocochlear nerve fibers?

The narrow duplicated internal auditory canal (IAC) is a very rare malformation, and there is no report about the narrow triplicated IAC in the literature. It has been believed to be associated with congenital sensorineural hearing loss and to be a result of aplasia or hypoplasia of the vestibulocochlear nerve or the cochlear branch. We present 2 cases of unilateral narrow duplicated IAC and 1 case of unilateral narrow triplicated IAC with ipsilateral sensorineural hearing loss. The separated, accessory bony canals delineated on high-resolution computed tomography do not mean the presence of nerve fibers. In previously presented cases and in our case, the separated small canals were vacant and without a cochlear nerve fiber. We present new common radiological findings as follows: the bony canal to the cochlea is very thin and the connection with the modiolus of the cochlea is interrupted in narrow separated IAC.