Unilateral auditory neuropathy spectrum disorder: retrocochlear lesion in disguise?

Objective: To investigate whether the aetiology for hearing impairment in neonates with unilateral auditory neuropathy spectrum disorder could be explained by structural abnormalities such as cochlear nerve aplasia, a cerebellopontine angle tumour or another identifiable lesion. Methods: In this prospective case series, 17 neonates were diagnosed with unilateral auditory neuropathy spectrum disorder on electrophysiological testing. Diagnostic audiology testing, including auditory brainstem response testing, was supplemented with computed tomography and/or magnetic resonance imaging. Results: Ten of the neonates (59 per cent) showed evidence for cochlear nerve aplasia. Of the remaining seven, four were shown to have another abnormality of the temporal bone on imaging. Only three neonates (18 per cent) were not diagnosed with cochlear nerve aplasia or another lesion. Three computed tomography scans were reported as normal, but subsequent magnetic resonance imaging revealed cochlear nerve aplasia. Conclusion: Auditory neuropathy spectrum disorder as a unilateral condition mandates further investigation for a definitive diagnosis. This series demonstrates that most neonates with unilateral auditory neuropathy spectrum disorder had pathology as visualised on computed tomography and/or magnetic resonance imaging scans. Magnetic resonance imaging is an appropriate first-line imaging modality