Relationship of Caudate and Thalamus Volumes to Autism Severity.

Abstract:
Goals: Autism is a neurodevelopmental disorder affecting cognitive, languistic, social, and emotional functioning. The current study examined the relationship between subcortical brain structures and autism severity. Methods: Sixteen autistic children aged 7-13 (IQ range: 50-132) underwent brain MRI imaging with quantitative image segmentation. Volumes of subcortical structures were measured and normalized as a ratio of total brain size to account for varying head size and age. Autism severity was assessed by the Autism Diagnostic Observation Schedule (ADOS), and subjects received neuropsychological and neurological exams. Results: There was a negative correlation between caudate volume and ADOS communication score (r= -0.55; p<0.03) and a positive correlation between thalamus volume and ADOS social score (r=0.50; p<0.05). Caudate and thalamus volumes were also inversely correlated with each other (r= -0.50; p<0.05). Conclusion: Autism severity as measured by ADOS communication and social scores demonstrated an inverse relationship with caudate volume and a positive relationship with thalamus volume, and these structures were negatively correlated with each other. This may indicate an abnormality in cortico-striato as well as cortico-thalamic connections. It could also indicate that the striato-thalamic interaction is imbalanced. While the etiology and brain pathology of autism remain under investigation, these observations may point toward one component of this complex debilitating disorder.