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

Abstract

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.

Duplicated internal auditory canal with dysplastic ossicles and microtia: role of high-resolution CT and MRI

“…Duplication of IAC (DIAC) is a very rare anomaly with less than 50 cases reported in the literature. 1 Imaging features of duplicated IAC and its…”

“…Duplication of IAC usually occurs unilaterally and is often associated with the aplastic/hypoplastic vestibulocochlear nerve. 1 It is important to differentiate IAC stenosis from DIAC on imaging because patients with IAC stenosis have dysplastic vestibulocochlear nerve and they usually benefit from electronic cochlear implantation, while cases with DIAC have aplastic/ hypoplastic nerve and are usually not benefited from electronic cochlear implantation. 2 3 External, middle and inner ear abnormalities are occasionally seen with DIAC which are additionally responsible for the hearing loss and need consideration while planning for surgery.…”

“…2 3 External, middle and inner ear abnormalities are occasionally seen with DIAC which are additionally responsible for the hearing loss and need consideration while planning for surgery. 1 Rarely, DIAC can be associated with syndromes like Klippel-Feil syndrome and pontine tegmental cap dysplasia. 4 Thus, HRCT followed by MRI is necessary for the complete evaluation of cases of DIAC.…”

Internal auditory canal duplication with facial and cochlear nerve dysfunction: A case report

“…2,3 Duplication of IAC is detected on High-Resolution Computed Tomography (HRCT) of the temporal bone, which could either be a partial or complete bony septum. 4 On magnetic resonance imaging (MRI), the vestibulocochlear nerve can be aplastic or hypoplastic. 4 Duplication of IAC may be associated with other inner, middle, or external ear anomalies.…”

“…4 On magnetic resonance imaging (MRI), the vestibulocochlear nerve can be aplastic or hypoplastic. 4 Duplication of IAC may be associated with other inner, middle, or external ear anomalies. Similarly, it may form a part of syndromic presentation such as Klippel-Feil syndrome.…”