In this situation, it is not possible to determine the amount of cochlear fibers travelling in the CVN. The presence of an unbranched cochleovestibular nerve (CVN) is a challenge in these cases. Even if the nerve is present, the distribution of the neural tissue in the abnormal cochlea is unpredictable, and ABI may be indicated in such cases if CI fails to elicit an auditory sensation. (3):Ĭommon cavity and incomplete partition type I cases if the cochlear nerve is present. The results of CI in cochlear aplasia and vestibular dilatation are not successful and this should be avoided. It is important to note that common cavity can be easily confused with cochlear aplasia and vestibular dilatation. If the cochlear nerve is present they are candidates for cochlear implantation. In conclusion, ABI can provide satisfactory audiological outcomes and language development to a certain extent is possible when every aspect of whole process is applied properly.Ĭommon cavity and incomplete partition type I cases where cochlear nerve is apparently missing. Overall complication rate is in an acceptable range when surgery is performed with an experienced team. Interindividual variability in language development and audiological outcome is prominent. Intraoperative eABR measurements are important to determine correct position of electrode. Surgical method of choice is retrosigmoid approach in children. Rehabilitative assessment is focused on auditory perception skills, language and speech skills and learning abilities. In preoperative audiological evaluation, subjective tests should always be included in test battery as well as objective ones. The side with less severe inner ear malformation or with more developed neural structures can be preferred. Preoperative radiological work up involves both high resolution computed tomography and magnetic resonance imaging. Better language outcome is expected at younger ages, i.e., between 1 and 2 years. Age limit for ABI is similar to CI candidate children. The ABI team must be experienced on pediatric CI patients, also an experienced pediatric neurosurgeon is indispensable to achieve success and to avoid complications. Further definitive diagnostic tools are require in order to overcome this uncertainty. Commonly, CI is the first choice in these patients if benefit with CI is not satisfactory during follow up, then ABI is utilized. Intracochlear electrical ABR (eABR) seems to a better indicator compared to preoperative electrophysiological tests. However, none of these assessment methods offer enough data to enable correct choice between CI and ABI. In these patients, radiological findings should be utilized together with preoperative and intraoperative audiological evaluation. Among probable indications, children with hypoplastic nerves constitute the most challenging group in decision making between cochlear implant (CI) and ABI. In this review article, definite and probable indications of ABI for children are stated. Use of ABI opened a new era for this group of patients. Until last decade, use of auditory brainstem implant (ABI) was restricted to adults and children with severe inner ear malformations and cochlear nerve aplasia did not have any option for hearing rehabilitation.
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