Auditory Processing Disorder as the Sole Manifestation of a Cerebellopontine and Internal Auditory Canal Lesion

Clinical importance of auditory processing disorder (APD) testing is often overlooked and regarded with skepticism given the challenging interpretation of results and the current growing debate of its nature and clinical entity.

Presentation of this case is highly educational as APD is the single clinical manifestation of a large cerebellopontine and internal auditory canal lesion.

A case report.

The patient underwent a standard audiological evaluation with normal results. She was referred for APD evaluation. The APD test battery consisted of speech in babble (SinB), dichotic digits (DD), frequency and duration of pattern sequence testing, Random Gap Detection Test, and gaps in noise. These were followed by otoacoustic emissions testing, auditory brainstem responses (ABR) and magnetic resonance imaging (MRI).

Her auditory processing results showed deficits in SinB and DD limited to the right ear as well as deficits in temporal processing. Both verbal and nonverbal tests exhibited deficits strictly limited to the right ear, which was in accordance with what she was experiencing as reduced loudness for the incoming sounds on the right ear. This less costly evaluation revealed that there was good reason to assess electrophysiologically the auditory system. ABR showed an abnormal waveform with either missing or severely prolongated wave V (depending on stimulus polarity). Otoacoustic emissions were normal. MRI was then implemented revealing a large cerebellopontine and internal auditory canal lesion.

This clinical case stresses the importance of testing for APD with a psychoacoustical test battery despite current debate of lack of a gold standard diagnostic approach to APD. In this case, APD diagnosis led to a cerebellopontine lesion identification with extension to the right internal auditory canal. This rare cause of APD demonstrates the efficiency of the current diagnostic test battery in revealing lesional causes of central APD.