Mismatch negativity in auditory neuropathy patients

ABSTRACT

Mismatch negativity [MMN] is a negative component in the auditory event-related potential. There has been increased interest in using the MMN as a clinical diagnostic tool because it might provide an objective neural measure of auditory discriminability. Auditory neuropathy [AN] is characterized by a paradoxical absence of auditory brainstem evoked potentials with presence of otoacoustic emissions, in patients whose pure-tone thresholds were slightly elevated. The present study was designed to investigate the detectability of MMN in cochlear hearing loss and AN patients and to test the effectiveness of MMN as an indicator of auditory discrimination at cortical level, particularly in patients with AN, if any. This study consisted of sixty subjects divided into three groups [Group 1] 20 AN patients, [group 2] 20 patients with bilateral moderate SNHL of cochlear origin and [group 3] 20 normal peripheral hearing subjects. All participants were submitted to full medical history, otoscopy, basic audiological evaluation. TEOAEs, ABR for neuro otologic diagnosis and MMN testing. The results of the present study demonstrated that SNHL had a significant impact on the timing of the brain processes involved in the detection and discrimination of stimuli. Moreover, no significant differences were found between AN patients and patients with cochlear hearing loss as far as MMN latencies