Novel Atypical Rhythmical Movement Identified in Middle-to-Old Aged Autistic Adults using Unified Parkinson’s Disease Rating Scale (UPDRS) Assessment

Abstract

Autism spectrum disorder (ASD) is a lifelong condition, yet most existing research focuses on autistic children, with limited understanding of aging in middle and old aged autistic adults. Several epidemiological studies and clinical observations found a striking prevalence of Parkinsonism in autistic adults, highlighting the urgent need to comprehensively understand the neuromotor degenerative processes in ASD. To fill this critical gap, we administered the Unified Parkinson’s Disease Rating Scale Part 3 (UPDRS-III) subtasks 3.4-3.8 in 35 autistic adults aged 30-73 and 25 matched neurotypical controls. During the assessment, our team identified a novel behavioral atypicality in autistic adults. This behavior, termed atypical rhythmic (AR) movements, differs from other repetitive behaviors in ASD and involves unintentional, rhythmic, small-amplitude movements in non-target body parts when the target body part was engaged in the assessment. For example, rhythmic toe-tapping, finger-tapping, and head-nodding of non-target limbs would qualify as AR behavior. We hypothesize that autistic individuals will have higher UPDRS scores than the general population and that the AR behavior will be qualitatively outlined. We report two key observations. First, autistic individuals scored significantly higher on UPDRS-III subtasks 3.4b, 3.7b, 3.8a, and 3.8b compared to neurotypical controls. Second, AR behaviors were found to manifest contralaterally, ipsilaterally, and centrally across various body appendages in autistic adults. Defining this behavior is clinically significant as it may reflect brain connectivity deficits commonly seen in autistic individuals. We speculate compromised corpus callosum circuitry and neural compensation may concurrently underlie AR behaviors in autistic adults. Future fMRI studies are needed to confirm its neural origins.