Caudate nucleus is enlarged in high-functioning medication-naive subjects with autism.

Background: Autism is defined by three symptom clusters, including repetitive and stereotyped behavior. Previous studies have implicated basal ganglia in these behaviors. Earlier studies investigating basal ganglia in autism have included subjects on neuroleptics known to affect basal ganglia volumes. Therefore, we investigated these structures in medication-naive subjects with autism.

Methods: Volumetric magnetic resonance measures of caudate, putamen, and nucleus accumbens were compared in two independent samples of medication-naive, high-functioning subjects with autism or Asperger syndrome: 1) 21 affected children and adolescents and 21 matched control subjects; and 2) 21 affected adolescents and young adults and 21 matched control subjects.

Results: Caudate nucleus was enlarged in both samples. This result remained significant after correction for total brain volume.

Conclusions: These results implicate caudate nucleus in autism, as an enlargement of this structure was disproportional to an increase in total brain volume in two independent samples of medication-naive subjects with autism.