Self-Injurious Behaviours Are Associated with Alterations in the Somatosensory System in Children and Adolescents with Autism Spectrum Disorders: A Multimodal Brain Imaging Study

Background: Children with autism spectrum disorders (ASD) commonly perform behaviours that are self-injurious, often in the absence of reporting pain. Previous research suggests that altered pain sensitivity is associated with morphological changes in somatosensory and limbic cortices. Self-injurious behaviours are reported to result in alterations in the structure and organization of the temporal lobes in adults with ASD. However, the effect of self-injurious behaviour on cortical development in children with ASD remains unknown.

Objectives: To determine the relation between grey/white matter structural changes and self-injurious behaviours in children and adolescents with ASD. 

Methods: We studied 28 children and adolescents (mean age=10.34 ±2.5 yrs; range: 6-15yrs; 25 males) who carried a clinical diagnosis of ASD. Participants were verbal and high functioning (IQ=104; sd=18.27). Self -injury was assessed using a standardized parental questionnaire. Each participant underwent diffusion tensor imaging (DTI) and T1-weighted magnetic resonance imaging at 1.5 Telsa (T). Cortical thickness analysis was performed on the anatomical images using the CIVET pipeline; based on a priori hypotheses, regions-of-interest were drawn over the bilateral somatosensory, cingulate, and medial temporal lobe cortices. Volumes of thalamic nuclei were extracted using non-linear alignment of a histological atlas. Tract-based spatial statistics were used to assess changes in Fractional Anisotropy (FA) using the DTI data set followed by whole brain tractography.

Results: Self-injury scores negatively correlated with thickness in the right superior parietal lobule (p=0.001). A directed search in the left primary somatosensory cortex (SI) also revealed a significant negative correlation with self-injury scores (p=0.006). Volumetric analyses revealed that the left ventroposterior (VP) nucleus was negatively correlated with higher self-injury scores (R=-0.53, p=0.005). Based on these findings we extracted the FA values, a measure of white matter fibre integrity, based on a tract based region of interest analysis between SI and the VP nucleus and found that children who engaged in self injury had significantly higher FA values in the left hemisphere (F=5, p=0.04).

Conclusions:  Cortical volume and thickness in primary and association somatosensory brain areas were lower in ASD children with increased self injury, suggesting that alterations in somatosensory brain regions, and the underlying white matter pathways, could serve as a biomarker for disrupted brain development in children with ASD who self injure. Future research will focus on the relation among altered brain morphology, self-injury and atypical pain perception commonly seen in this population.