Original Research Article Indian Journal of Anatomy and Surgery of Head, Neck and Brain, October-December, 2015: 1-12 1 Comparison of Binaural Interaction Component (BIC) in Symmetrical and Asymmetrical Hearing Loss: Pilot Study Adarsh 1 , George Sebastian 2 , Himanshu Kumar Sanju 3 , Rajalakshmi Krishna 4 1,3 Graduate Student, 2 PG Student, 4 Professor, Department of Audiology, All India Institute of Speech & Hearing, Karnataka Corresponding Author: Himanshu Kumar Sanju Graduate Student, Department of Audiology, All India Institute of Speech & Hearing, Karnataka E-mail: himanshusanjuaiish@gmail.com Abstract Background and Objective: Binaural interaction component has been seen to be effective in assessing the binaural interaction process in normal hearing individuals. However, there is a lack of literature regarding the effects of SNHL on the Binaural Interaction Component of ABR. Hence, it is necessary to study binaural interaction occurs at the brainstem when there is an associated hearing impairment. Methods: Three groups of participants in the age range of 30 to 55 years were taken for study i.e. one control group and two experimental groups (symmetrical and asymmetrical hearing loss). The binaural interaction component was determined by subtracting the binaurally evoked auditory potentials from the sum of the monaural auditory evoked potentials: BIC= [{left monaural + right monaural)-binaural}. The latency and amplitude of V th peak was estimated for click evoked ABR for monaural and binaural recordings. Results: One way ANOVA revealed a significant difference for binaural interaction component in terms of latency between different groups. One-way ANOVA also showed no significant difference seen between the three different groups in terms of amplitude. Conclusion: The binaural interaction component of auditory brainstem response can be used to evaluate the binaural interaction in symmetrical and asymmetrical hearing loss. This will be helpful to circumvent the effect of peripheral hearing loss in binaural processing of the auditory system. Additionally the test does not require any behavioral co- operation from the client, hence can be administered easily. Keywords: BIC, symmetrical, asymmetrical, hearing loss, ABR, Binaural interaction Introduction Sensorineural hearing loss (SNHL) is probably the most common form of hearing loss and this type of hearing loss not only lead to elevation of threshold for detection of sound but, also the affects the way in which sound is perceived. The perception of speech in individual with SNHL is also dependent on the configuration of hearing loss. Sensorineural hearing loss can be symmetrical or asymmetrical. Asymmetrical sensory neural hearing loss is defined as binaural difference in bone conduction thresholds of greater than 10dB at two consecutive frequencies or greater than15dB at one frequency (0.25 to 8.0KHZ) and a difference of greater than 15 dB in the maximum speech discrimination score is also significant. Symmetrical sensorineural hearing loss refers to the same or similar degree of hearing loss in both ears. So the people with asymmetrical hearing loss expected to have problem in binaural hearing. Cochlear hearing loss leads to both frequency and temporal problems, resulting in poor frequency and temporal resolution abilities, i.e. reduction in the ability to resolve the frequency components of complex sounds and reduced ability to process the temporal fine structure of sounds. One of the major consequences of such a type of reduction in resolution is the reduction in the ability to process binaural signals. Binaural processing is the degree to which interactions take place between the two ears. If no interaction occurs between the two ears, then it is expected that the binaural system has been compromised. Binaural cues provide the basis for judgments on sound direction. Binaural hearing has distinct advantages in terms of sound localization and hearing in noise over monoaural hearing and also for binaural loudness summation and binaural release from masking.