Prefrontal rTMS Treatment Effects on Autonomic Activity in Children with Autism

Autism spectrum disorder (ASD) is a developmental disorder marked by difficulty in social interactions and communication. Children with ASD also often present symptoms of autonomic nervous system (ANS) functioning abnormalities, featured by predominantly sympathetic over-activation and low parasympathetic tone. In prior studies of our group we reported positive behavioral outcomes of neuromodulation based on low frequency repetitive transcranial magnetic stimulation (rTMS) in autism using various length of treatment course and site of prefrontal stimulation. The objective of this study was to determine the effect of 12 sessions of weekly rTMS treatments on autonomic function in 30 children with autism (mean age around 14.2 years) by recording electrocardiogram (EKG) and electrodermal activity during each rTMS session using C-2J&J Engineering Inc. monitor. Heart rate variability (HRV) measures such as R-R intervals, standard deviation of cardiac intervals, pNN50, power of high frequency (HF) and low frequency (LF) components of HRV spectrum, LF/HF ratio, were then derived from the recorded EKG and analyzed off-line using Kubios software. We expected that the course of 12 weekly inhibitory low-frequency rTMS applied to the dorsolateral prefrontal cortex (DLPFC, 6 sessions at the left, 6 at the right DLPFC) would improve autonomic balance probably through improved frontal inhibition of limbic activity, and will be manifested in decreased overall heart rate, increased HRV in a form of increased HF power, decreased LF power, resulting in decreased LF/HF ratio and decreased SCL. In addition we analyzed changes of heart rate and SCL on minute-by-minute basis in each rTMS session to evaluate ANS activity changes during procedure. Our post-12 TMS results show significant increases in cardiac intervals variability measures and decrease of tonic SCL indicative of increased cardiac vagal control and reduced sympathetic arousal. HR slowing and SCL decreases were also significant during rTMS. We could not find any significant differences between autonomic effects depending on the stimulated hemisphere as both left and right DLPFC rTMS showed similar autonomic outcomes and main changes were driven by the number of rTMS treatments. Behavioral evaluations completed by parent showed decreased irritability, hyperactivity, stereotype behavior and compulsive behavior ratings. Keywords * Autism spectrum disorder * Transcranial magnetic stimulation * Children * Autonomic activit