Evaluation of sympathetic sudomotor responses to auditory stimuli in children with autism spectrum disorders

AIM AND OBJECTIVE: Autism spectrum disorder (ASD) being a complex neurological and developmental disorder is also associated with autonomic nervous system dysfunction. Sudomotor nerve function is one highly sensitive index of sympathetic cholinergic activity and can be evaluated by measuring sympathetic skin response (SSR) to various stimuli. Studies reporting SSR to auditory stimulus among ASDs are limited and to the extent of our knowledge not assessed in the Indian scenario. The objective of the study was to assess and compare sympathetic sudomotor activity by evaluating SSR to auditory stimuli in children with and without ASDs. MATERIALS AND METHODS: A total of eighty individuals were enrolled in the study, including forty children with ASD and forty typically developing (TD) children. SSR to auditory stimulus was assessed using a digitized data acquisition unit in a soundproof room, maintained at 23°C. SSR indices such as latent period (s), amplitude (mv), and habituation were analyzed and compared using appropriate statistical tests between the groups. P < 0.05 was considered statistically significant. RESULTS: Habituation for SSR was statistically significantly lower (P < 0.001) in children with ASD (0.43 [0.21, 0.61]) compared to TD children (0.78 [0.65, 0.95]). Latent period was also statistically significantly higher in children with ASD (1.67 [1.37, 2.02]) compared to TD children (1.41 [1.2, 1.72]). However, there was no significant difference in amplitude values between the groups. CONCLUSIONS: Children with ASDs exhibited slower habituation of SSR to auditory stimuli compared to healthy controls. This slower habituation process might be due to the persistent predominant state of sympathetic nerves, which, in turn, contributes to the atypical emotional and behavioral traits prevailing in ASDs.