Correlation between vHIT and caloric test in individuals with Auditory Neuropathy Spectrum Disorder

Abstract

Auditory neuropathy spectrum disorder features the presence of Otoacoustic emissions, poor speech identification scores and absent auditory brainstem response. The present study aimed at correlation between vHIT and caloric test in individual with ANSD. Standard group comparison was performed in the study. Total 30 individuals participated in the study where Group I consisted 15 individuals with auditory neuropathy spectrum disorder and Group II consisted 15 normal hearing individuals. All participants underwent case history, pure tone audiometry, immittance, otoacoustic emissions, auditory evoked response, caloric test and video head impulse test. Based on the Hex plot, the vHIT response was analysed where the VOR gain of each of all six semi-circular canals and the refixation saccades (if any) at the time of head thrust i.e. covert saccade, after the head thrust i.e. overt saccade were represented. Similarly, in case of caloric test, the cumulative frequency was taken in consideration to be denoted on the butterfly chart. The four response waves achieved with bi-thermal stimulation were calculated and the cumulative frequency was achieved. All the tests were performed within noise permissible criteria of ANSI S3.1 (1991) in an acoustically treated room. Shapiro-Wilk test revealed normal distribution of the data (p>0.05). Hence a parametric independent sample't' test was done to compare the VOR gain and VOR gain asymmetry between the normal individuals and individuals with auditory neuropathy spectrum disorders. Pearson correlation test was done to check the Correlation between VOR gain and duration of six semi-circular canals in individual with ANSD. Also, Pearson's correlation was performed to understand the relation between the VOR gain and VOR gain asymmetry with the duration of disease in individuals with ANSD. Independent sample 't' test revealed significantly lower vestibulo-ocular reflex gain values in individuals with auditory neuropathy spectrum disorder. Presence of 100% corrective refixation saccades was seen in the same group. Pearson's correlation revealed no significant correlation between vestibulo-ocular reflex gain with duration of hearing loss and puretone thresholds for any of the three orthogonal planes. Huge percentage of individuals with auditory neuropathy spectrum disorderhave been found to have associated vestibular dysfunction as well. Therefore, video head impulse testcan be usedas one of the important tests of vestibular test battery to evaluate all six semi-circular canals in individuals with auditory neuropathy spectrum disorder.