Is a narrow internal auditory meatus a contraindication to cochlear implants?

Abstract

The finding of an abnormality such as a narrow internal auditory meatus (IAM) on computed tomography (CT) raises the possibility that the cochlear nerve may be aplastic or hypoplastic and non-functional. Shelton et al. (1989) reported that three children with the anomaly of narrow IAM had received cochlear implants but failed to show an auditory response to sound stimulation. Since then, identification of this problem on screening image analysis has been a contraindication to cochlear implantation. However, Acker et al. (2001) mentioned that if definite responses to sound are present in either ear, implantation should be considered, even though imaging of the cochlear nerve is uncertain. We report that the promontory electrically evoked auditory brainstem response (EABR) is useful in deciding the candidacy for cochlear implant even in cases with very poor sound responses, very narrow IAM (1–2 mm) and also an uncertain image of the cochlear nerve on magnetic resonance imaging (MRI).