Brain anatomy, gender and IQ in children and adolescents with fragile X syndrome

This study utilized MRI data to describe neuroanatomical morphology in chil dren and adolescents with fragile X syndrome, the most common inherited cau se of developmental disability. The syndrome provides a model for understan ding how specific genetic factors can influence both neuroanatomy and cogni tive capacity. Thirty-seven children and adolescents with fragile X syndrom e received an MRI scan and cognitive testing. Scanning procedures and analy tical strategies were identical to those reported in an earlier study of 85 typically developing children, permitting a comparison with a previously p ublished template of normal brain development. Regression analyses indicate d that there was a normative age-related decrease in grey matter and an inc rease in white matter. However, caudate and ventricular CSF volumes were si gnificantly enlarged, and caudate volumes decreased with age. Rates of redu ction of cortical grey matter were different for males and females. IQ scor es were not significantly correlated with volumes of cortical and subcortic al grey matter, and these relationships were statistically different from t he correlational patterns observed in typically developing children. Childr en with fragile X syndrome exhibited several typical neurodevelopmental pat terns. Aberrations in volumes of subcortical nuclei, gender differences in rates of cortical grey matter reduction and an absence of correlation betwe en grey matter and cognitive performance provided indices of the deleteriou s effects of the fragile X mutation on the brain's structural organization.