Amygdala Enlargement in Toddlers with Autism Related to Severity of Social and Communication Impairments

• Published in: Biological psychiatry (1969) 2009-11, Vol.66 (10), p.942-949
• Main Authors: Schumann, Cynthia Mills, Barnes, Cynthia Carter, Lord, Catherine, Courchesne, Eric
• Format: Article
• Language: English
• Subjects: Amygdala - pathology; Analysis of Variance; Autistic Disorder - complications; Autistic Disorder - pathology; Biological and medical sciences; Brain growth; Child clinical studies; Child, Preschool; Communication Disorders - etiology; Communication Disorders - pathology; development; Developmental disorders; Female; Functional Laterality - physiology; Humans; Image Processing, Computer-Assisted - methods; Infant; Infantile autism; Linear Models; Magnetic Resonance Imaging - methods; Male; Medical sciences; MRI; neuroanatomy; Psychiatry; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Sex Factors; Social Behavior Disorders - etiology; Social Behavior Disorders - pathology; temporal; volume
• ISSN: 0006-3223; 1873-2402
• DOI: 10.1016/j.biopsych.2009.07.007

Background Autism is a heterogeneous neurodevelopmental disorder of unknown etiology. The amygdala has long been a site of intense interest in the search for neuropathology in autism, given its role in emotional and social behavior. An interesting hypothesis has emerged that the amygdala undergoes an abnormal developmental trajectory with a period of early overgrowth in autism; however this finding has not been well established at young ages nor analyzed with boys and girls independently. Methods We measured amygdala volumes on magnetic resonance imaging scans from 89 toddlers at 1–5 years of age (mean = 3 years). Each child returned at ∼5 years of age for final clinical evaluation. Results Toddlers who later received a confirmed autism diagnosis (32 boys, 9 girls) had a larger right ( p < .01) and left ( p < .05) amygdala compared with typically developing toddlers (28 boys, 11 girls) with and without covarying for total cerebral volume. Amygdala size in toddlers with autism spectrum disorder correlated with the severity of their social and communication impairments as measured on the Autism Diagnostic Interview and Vineland scale. Strikingly, girls differed more robustly from typical in amygdala volume, whereas boys accounted for the significant relationship of amygdala size with severity of clinical impairment. Conclusions This study provides evidence that the amygdala is enlarged in young children with autism; the overgrowth must begin before 3 years of age and is associated with the severity of clinical impairments. However, neuroanatomic phenotypic profiles differ between males and females, which critically affects future studies on the genetics and etiology of autism.