Anatomical correlates of normal and impaired language in a set of dizygotic twins.

This report presents findings for a set of dizygotic twins at age 4 years 9 months. The male was diagnosed as specifically language impaired. For both children, the left-right perisylvian configuration was atypical. Only the male's configuration was symmetrical, a finding in line with autopsy data reported for subjects with "developmental dyslexia" who also may have had a form of language impairment. In addition, the male had an atypical (L greater than R) configuration of the cerebral hemispheres, a finding not seen in his twin, or in a series of volunteers without a history of developmental language impairment. The in utero effects of gonadal hormones that may account for these findings are discussed.