Workup
Approach Considerations
In patients with congenitally acquired anomalous inner ears, high-resolution computed tomography (CT) scanning and magnetic resonance imaging (MRI), of the temporal bone, are the diagnostic tools of choice in diagnosing the disorder. (See the CT scan below.) [16]
Incomplete partition anomalies of the cochlea. A and B: Incomplete partitions. Cochlea (C), without the modiolus and interscalar septa, resembles an empty cystic structure (A) and is accompanied by dilated vestibule (v) (B). C and D: Incomplete partition type II. The apical part of the modiolus and the corresponding interscalar septa are defective (black arrow), giving the apex of the cochlea a cystic appearance due to the confluence of middle and apical turns (C). This is accompanied by minimally dilated vestibule (v) and large vestibular aqueduct (white arrow). E: Incomplete partition type III. Cochlea has interscalar septa (black arrow), but the modiolus is completely absent. Published by Cochlear Implants International.
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CT Scanning
High-resolution CT scanning of the temporal bone should be obtained to assist in diagnosis and can be particularly useful in classification of the cochlear malformation. Assessing the width of the internal auditory canal and course of the facial nerve is easily performed using high-resolution CT scanning.
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MRI
MRI is useful in assessing soft tissues of the temporal region, specifically the presence or absence of the eighth cranial nerve in the internal auditory canal.
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Media Gallery
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Schematic representation of the normal cochlea and cochlear malformations. A: normal cochlea, mid-modiolar section; Mo = modiolus, CA = cochlear aperture, B = basal turn, M = middle turn, A = apical turn, arrowheads = interscalar septa. B: Normal cochlea, inferior section passing through the round window niche (RWN); arrowhead = interscalar septum between middle and apical turns. C: Cochlear aplasia with normal vestibule. D: Cochlear aplasia with enlarged vestibule. E: Common cavity. F: Incomplete partition type I. G: Incomplete partition type II. H: Incomplete partition type III. I: Cochlear hypoplasia, bud type (type I). J: Cochlear hypoplasia, cystic cochlea type (type II). K: Cochlear hypoplasia, with less than 2 turns (type III).
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Incomplete partition anomalies of the cochlea. A and B: Incomplete partitions. Cochlea (C), without the modiolus and interscalar septa, resembles an empty cystic structure (A) and is accompanied by dilated vestibule (v) (B). C and D: Incomplete partition type II. The apical part of the modiolus and the corresponding interscalar septa are defective (black arrow), giving the apex of the cochlea a cystic appearance due to the confluence of middle and apical turns (C). This is accompanied by minimally dilated vestibule (v) and large vestibular aqueduct (white arrow). E: Incomplete partition type III. Cochlea has interscalar septa (black arrow), but the modiolus is completely absent. Published by Cochlear Implants International.
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