Subjective and Objective Estimate of Neural Fatigue in an Adult with Auditory Neuropathy Spectrum Disorder

Abstract

Auditory neuropathy spectrum disorder (ANSD) is a retrocochlear disorder in which cochlear functioning is normal but the transmission in the auditory neural pathway is affected. The present study reports of neural fatigue seen in subjective and objective tests of adaption in a 19 year old adult with ANSD. He had bilateral mild sensorineural hearing loss with otoacoustic emissions present and absent auditory brainstem response. Immittance evaluation showed elevated acoustic reflexes at 500 Hz and 1000 Hz in both ipsilateral and contralateral stimulation. Reflex decay test was administered at 500 Hz and 1000 Hz which showed positive reflex decay with contralateral stimulation. Olsen and Noffsinger tone decay test and supra-threshold adaptation test showed positive tone decay at 500 Hz, 1000 Hz and 2000 Hz in both ears. The results of the study showed positive reflex decay and positive tone decay which indicate abnormal neural fatigue. The abnormal neural firing seen in individuals with ANSD could have resulted in positive reflex decay and tone decay. However, further studies on larger group of population are essential for further understanding the mechanisms in detail.