Duplicated Internal Auditory Canal Research Articles

De novo sensorineural hearing loss sequelae of narrow, duplicated internal auditory canal: Case series and literature review.

IntroductionA narrow duplicated internal auditory canal (IAC) is an extremely rare anomaly, likely associated with congenital sensorineural hearing loss due to aplasia/hypoplasia of the vestibulocochlear nerve or the cochlear branch alone. We aimed to review our experience with IAC duplication, describe its clinical characteristics, and present a literature review.Case presentationOur Otology database was searched for children who showed duplication of the IAC. Clinical characteristics of two children with bilateral duplication of the IAC are described. Data regarding clinical history, auditory assessment, magnetic resonance imaging (MRI), and computed tomography (CT) were collected and analyzed. The separated, accessory bony canals were demonstrated on high-resolution CT scans, and the nerves were demonstrated on MRI.DiscussionTo date, a few cases of narrow duplicate IAC have been reported in the literature, Approximately 20% of patients with congenital SNHL are found to show inner-ear bony abnormalities on CT, but much uncertainty still exists about the mechanism underlying IAC stenosis.5 Imaging findings of the temporal bone in our case series demonstrated asymmetrical narrowing of both IACs, there is no clear evidence in the literature supporting the predominance of one side over the other. In our series, facial nerve function was intact bilaterally. As for our cases, both patients were enrolled in a single-sided deafness evaluation for a trial of options such as BAHA, CROS, cochlear implants, and other non-implantable hearing aids. Furthermore, addressing the important factors will optimize the outcomes including surgery at early age to optimize neural plasticity, with intense long-term therapy.ConclusionCongenital duplication of the IAC likely convoying sensorineural hearing loss due to aplasia/hypoplasia of the vestibulocochlear nerve. Early diagnosis and intervention are essential to optimize patient outcomes.

The Narrow Internal Auditory Canal with Triplication on the Left Side and with Duplication on the Right Side: Radiological Findings

The constricted internal auditory canal with duplication or triplication of the temporal bone is a very rare anomaly with only 23 cases in 16 reports in the literature, and only one of them is a constricted triplicated internal auditory canal (IAC) in which contralateral IAC is normal. We present the case with the right-sided constricted duplicated IAC and the left-sided narrow triplicated internal auditory canal. Computerized tomography (CT) revealed that the internal auditory canals separated by a bony septum into two canals on the right lateral and into three canals on the left lateral. Manyetik resonance (MR) imaging showed bilateral aplasia of cohlear nerve.

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

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

Duplicated internal auditory canal and dolichoectasia causing bilateral profound deafness in an adult

Inner ear malformations contributing to bilateral profound hearing loss in adulthood are extremely rare. High-resolution computed tomography of the temporal bones and magnetic resonance imaging revealed unilateral duplicated internal auditory canal (IAC) and bilateral semicircular canal aplasia in such an adult. This is only the fourth reported case in literature known to us of duplicated IAC in adults and first in which there is a description of isolated bilateral lateral semicircular canal aplasia as the sole labyrinthine abnormality. Dolichoectasia of the vertebrobasilar artery was also present in the contralateral ear causing compression of the cochlear nerve and profound deafness in the other ear for which cochlear implantation was done.

Pontine tegmental cap dysplasia accompanied by a duplicated internal auditory canal.

Pontine tegmental cap dysplasia accompanied by a duplicated internal auditory canal.

Congenital Hearing Loss and Internal Auditory Canal Anomalies: Imaging Findings and Implications for Management

Objectives: Approximately 20% of patients with congenital sensorineural hearing loss are found to have a radiologically proven inner ear anomaly. Of the inner ear abnormalities, duplication of the internal auditory canal is rare. We sought to describe clinical characteristics and treatment results of patients found to have duplicated internal auditory canal on imaging. Methods: This case series identified patients from over a 2 year period obtained in a random manner from teaching files and daily case material. Imaging findings, clinical characteristics, audiology testing and treatment were reviewed. Results: A total of 7 patients were identified with a total of 12 ears (2 patients had unilateral presentation). Three patients in this series had a history of branchio-oto-renal syndrome. All patients had high-resolution computerized tomography (CT) performed. Two patients had magnetic resonance imaging (MRI) performed. All patients had audiogram evaluation. Six patients had sensorineural hearing loss, and one patient had conductive hearing loss. As hearing loss became more severe as documented by decibels of hearing loss on audiogram, increasing number of middle and inner ear anomalies were found on imaging. Conclusions: This series is one of the largest series to evaluate duplicated internal auditory canal in conjunction with cochlear anomalies. MRI is a useful adjunct to evaluate presence of the cochlear nerve and should be considered in patients undergoing cochlear implantation with findings of duplicated internal auditory canal on CT scan. More severe hearing loss may be indicative of potential for more anomalies found on imaging.

Pontine Tegmental Cap Dysplasia

Pontine tegmental cap dysplasia (PTCD) is a rare congenital malformation. Clinical and imaging findings in 3 patients and the authors' experience with bilateral cochlear implantation in 1 patient are described. Retrospective review. Two tertiary medical centers. Three patients were evaluated by an otolaryngologist and underwent magnetic resonance imaging (MRI) of the temporal bones and brain. High-resolution computed tomography (CT) scanning of the temporal bones was performed in 2 patients. Imaging findings of the brain, the presence and course of resolvable cranial nerves, the membranous labyrinth, and internal auditory canals were reviewed. Clinical data were reviewed. All patients demonstrated typical brain characteristics of PTCD. Mild, bilateral cochlear dysplasia was noted in 2, and all had a normal vestibular labyrinth. The cochleovestibular nerves were universally absent bilaterally. The facial nerves were subjectively deficient bilaterally in 1 patient, unilaterally in the second patient, and normal in the third. An accessory canal for the seventh cranial nerve, referred to as a duplicated internal auditory canal, was present in all patients. Auditory brainstem response testing revealed profound bilateral sensorineural hearing loss in all of the patients; none suffered facial weakness. A single patient underwent bilateral cochlear implantation with only minimal response. The authors report 3 cases of PTCD with emphasis on imaging of the seventh and eighth cranial nerves and clinical neurotologic findings. All patients manifested duplicated internal auditory canals, a previously unreported finding in PTCD. Bilateral profound sensorineural hearing loss is due to absence of the cochleovestibular nerve. Prognosis for cochlear implantation is poor.

Bilateral narrow duplication of the internal auditory canal

To demonstrate diagnostic imaging of an extremely rare presentation of bilateral narrow duplication of the internal auditory canal. 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. 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.

Narrow Duplicated Internal Auditory Canal

Anarrow duplicated internal auditory canal (IAC) is a very rare congenital inner ear malformation, with only 5 cases (to our knowledge) reported in the literature. 1-5 A 14-year-old girl with unilateral sensorineural hearing loss (SNHL) showed 2 narrow 1 mm) bony canals in the inner ear portion of the left temporal bone on computed tomograms (CTs). The anterior canal continued to the bony canal of the facial nerve, and the posterior canal continued to the cochlea. Other than a lack of development of the canal for the cochlear nerve, the cochlea was normal. High-resolution magnetic resonance images (MRIs) revealed a single thin cranial nerve located in the anterior canal. However, a cranial nerve was not found in the posterior canal. Therefore, a diagnosis of a unilateral narrow duplicated IAC with a hypoplastic vestibulocochlear nerve and vestibular-semicircular canal malformation was made. Computed tomography plays an important role in the evaluation of the bony structure; however, assessment of the neural contents on MRIs is important for the appropriate diagnosis and treatment of patients with a narrow duplicated IAC. We report a case of a unilateral narrow duplicated IAC, with a particular emphasis on the imaging findings of thin-slice high-resolution CTs and MRIs.

Narrow Duplicated or Triplicated Internal Auditory Canal (3 Cases and Review of Literature)

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.

Bilateral narrow duplicated internal auditory canal

Internal auditory canal (IAC) anomalies are rare malformations that may include alterations of shape, size or orientation of the IAC. Bilateral duplication of IAC is a very rare malformation and only one case has been described in literature. We report a case of bilateral duplicated IAC together with other inner ear anomalies.

Narrow duplicated internal auditory canal: radiological findings and review of the literature

Narrow duplicated internal auditory canal (IAC) is a rare malformation of the temporal bone that is associated with ipsilateral congenital sensorineural hearing loss. This may be an isolated finding or a part of a syndrome. Radiological examination should demonstrate aplasia or hypoplasia of the neural components of the narrow IAC, to guide the surgical approach. We report a 7-year-old boy with Klippel-Feil syndrome with a narrow double IAC with no sensorineural hearing loss but with conductive hearing loss. In this patient, the IAC consisted of two separate narrow bony canals clearly seen on 3D temporal bone CT and one nerve that was delineated on MRI. The contralateral external auditory canal was stenotic and the ossicles were dysplastic.