Classification and Current Management of Inner Ear Malformations

Abstract

Morphologically congenital sensorineural hearing losscan be investigated under two categories. The majorityof congenital hearing loss causes (80%) are membranousmalformations. Here, the pathology involves inner earhair cells. There is no gross bony abnormality and,therefore, in these cases high-resolution computerizedtomography and magnetic resonance imaging of thetemporal bone reveal normal findings. The remaining20% have various malformations involving thebony labyrinth and, therefore, can be radiologicallydemonstrated by computerized tomography andmagnetic resonance imaging. The latter group involvessurgical challenges as well as problems in decisionmaking.Some cases may be managed by a hearing aid,others need cochlear implantation, and some cases arecandidates for an auditory brainstem implantation (ABI).During cochlear implantation, there may be facial nerveabnormalities, cerebrospinal fluid leakage, electrodemisplacement or difficulty in finding the cochlea itself.During surgery for inner ear malformations, the surgeonmust be ready to modify the surgical approach or choosespecial electrodes for surgery. In the present reviewarticle, inner ear malformations are classified accordingto the differences observed in the cochlea. Hearing andlanguage outcomes after various implantation methodsare closely related to the status of the cochlear nerve, anda practical classification of the cochlear nerve deficiencyis also provided.