Head circumference normal at birth, diverges from other groups at around 4 to 6 months of age
TUESDAY, Nov. 29 (HealthDay News) -- Boys with regressive autism have abnormal brain enlargement, with a head circumference that diverges from other groups at age 4 to 6 months, according to a study published online Nov. 28 in the Proceedings of the National Academy of Sciences.
Christine Wu Nordahl, Ph.D., from the University of California in Sacramento, and colleagues examined the relationship between total brain volume and autism onset status. The association was investigated in 2- to 4-year-old boys and girls with autism spectrum disorders, with (61 children) or without (53 children) regression, and 66 age-matched typically developing controls. Head circumference measurements were retrospectively assessed from birth through 18 months of age.
The investigators found that boys with regressive autism most frequently had abnormal brain enlargement. There was no difference in brain size among boys without regression and controls. Retrospective head circumference measurements showed that, at birth, head circumference was normal in boys with regression, and that at around the age of 4 to 6 months, it diverged from that seen in other groups. For girls with autism, there were no differences in brain size.
"These results suggest that there may be distinct neural phenotypes associated with different onsets of autism. For boys with regressive autism, divergence in brain size occurs well before loss of skills is commonly reported," the authors write.