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Cochlear Aplasia Presenting With Left Mixed Hearing Loss
An 8-year-old child with left mixed hearing loss is found to have left cochlear aplasia.
Imaging overview:
Axial non-contrast CT of the left ear shows complete absence of the cochlea and cochlear aperture. The internal auditory canal is small, the cochlear promontory is flattened, and the ossicles are normal. The anterior genu of the facial nerve has an obtuse angle, and the vestibule and lateral semicircular canal are malformed.
Clinical insight:
Cochlear aplasia is a rare inner ear malformation in which the cochlea fails to develop. It is usually associated with profound sensorineural hearing loss, so the mixed loss in this child warrants assessment of the middle ear. The stapes and oval window can be abnormal in some cases. The normal cochlea lies anterior to the internal auditory canal, so its absence with a small canal should prompt review of the full inner ear. Because standard cochlear implantation is not possible without a cochlea, recognizing this malformation can redirect management toward alternatives such as an auditory brainstem implant.
Case courtesy of Karen Moeller, MD, Texas Children’s Hospital.