The relationship between stereotypical movement disorder and neuroinflammation

Stereotypic movement disorder (SMD) is a neurodevelopmental condition frequently co-occurring with autism spectrum disorder (ASD), yet its underlying pathophysiology remains poorly understood. Emerging evidence suggests that neuroinflammatory mechanisms may contribute to the etiology of neurodevelopmental disorders. Based on this, we aimed to investigate the potential role of neuroinflammation, specifically interleukin-1β (IL-1β) and interleukin-6 (IL-6), in the etiopathophysiology of both primary SMD and ASD.

This cross-sectional study included children and adolescents aged 6-18 years, categorized into four groups: 22 with primary SMD, 20 with ASD and comorbid SMD (secondary SMD), 18 with ASD without SMD, and 18 healthy controls. Participants were assessed using the Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version (K-SADS-PL), Childhood Autism Rating Scale (CARS), Repetitive Behavior Scale-Revised Turkish Version (RBS-R-TV), and Conners Parent Rating Scale-Revised Short Form (CPRS-RS). Plasma IL-1β and IL-6 levels were measured using enzyme-linked immunosorbent assay (ELISA).

IL-1β and IL-6 levels were significantly higher in the primary SMD and ASD groups compared to healthy controls. Both cytokines were significantly correlated with stereotyped behavior severity and emerged as significant predictors in regression analyses.

Our findings suggest that neuroinflammatory processes may play a role in the pathophysiology of primary SMD and ASD, and that elevated cytokine levels are associated with greater stereotypy severity. To our knowledge, this is the first clinical study to explore these relationships in primary SMD. Further studies using larger samples and broader inflammatory panels are needed to validate and extend these findings.