Brain Structural Changes Caused by Autism Spectrum Disorder Based on Volumetric Analysis of Magnetic Resonance Images: A Review Study

Autism spectrum disorder (ASD) is a psychiatric disorder which occurs in early years of life and causes various individual and social problems. Early detection of autism would help in taking necessary precautions and preventing its adverse side effects. In this paper, we reviewed the articles that have investigated brain structural changes caused by ASD based on brain volumetric analysis in magnetic resonance images. We studied 37 papers about brain volume measurement, 34 articles concerning brain structural changes in autistic patients, 9 about brain functional changes, and 15 on major causes, diagnosis, and treatment of autism. According to literature, autism leads to whole brain enlargement (1.58%-10%). ASD was reported to cause increase in the volume of left anterior temporal gyrus, left posterior cingulate gyrus, right calcarine sulcus, left and right lingual gyrus, left precuneus, and right thalamus. But, no considerable volume changes were detected in the white matter. Also, autistic patients were found to have lower activity in the fusiform gyrus and broca region compared to normal subjects. Brain structural analysis using magnetic resonance imaging provides promising evidences for early detection of autism in children younger than three years of age. However, to evaluate brain structural changes in autistic patients, considering the theory of age-specific anatomic abnormalities (brain enlargement in childhood and brain volume decrease in adulthood), gender, and intelligence quotient are necessary.