Stable auditory evoked potentials in the study of two patients with auditory neuropathy

Introduction: We described the results of the auditory multiple steady state response (MSSR) technique in the assessment of two patients with auditory neuropathy (AN). The aim of this study was to corroborate the correspondence between the MSSR generators elicited by amplitude modulated tones ranging between 80-100 Hz, with the generators of auditory brain stem response (ABR). Moreover, we would also try to demonstrate the validity of the MSSR in the diagnosis of AN in children. Material and Methods: Two children diagnosed of hyperbilirrubinemia, aged, 18 months and 10 years have been studied with MSSR (500, 1000, 2000 and 4000Hz); ABR with clicks; OAE; behavioural audiometry; MRI and acoustic reflexes. Results: A difference between electrophysiological and behavioural audiogram in both cases diagnosed with auditory neuropathy have been found. The auditory thresholds were similar using the two types of evoked potentials (MSSR and ABR). Both techniques showed an increment of auditory threshold congruous with a severe auditory impairment, while behavioural audiometry showed only a mild elevation of auditory threshold. We can also see how the threshold differed between frequencies using behavioral audiometry and MSSR. Conclusion: It is concluded that our findings are in agreement with previous studies and they sustain the theory about the coincidence of MSSR at fast rate (80-110 Hz) and ABR generators. Also, we demonstrate the usefulness of the MSSR as an objetive electroaudiometric tool in patients with auditory neuropathy as ABR. This technique is thus a recommendable test to complete the audiological study in infants with AN, to establish a more precise treatment.