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.
Key Words
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Article info
Publication history
Published online: September 03, 2009
Accepted:
July 10,
2009
Received in revised form:
July 8,
2009
Received:
February 26,
2009
Identification
Copyright
© 2009 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.
