Neuroanatomy in adolescents and young adults with 22q11 deletion syndrome: comparison to an IQ-matched group.

22q11 deletion syndrome (22q11DS) is a common genetic condition associated with learning disability and high risk for psychiatric illness, in particular schizophrenia. Previous neuroimaging studies in children and adults with 22q11DS have uncovered a number of abnormalities, but have not differentiated between features relating to cognitive impairment and features relating to risk for schizophrenia. This structural MRI study compares adolescents with 22q11DS (n=14) to adolescents with idiopathic learning disability (n=13) and to typically-developing controls (n=14). Voxel-based morphometry and region-of-interest volumetric analyses were employed to test specific hypotheses based on prior studies of 22q11DS. Features that differentiated 22q11DS participants from both matched-IQ and higher-IQ controls were total white matter volume reduction, occipito-parietal and anterior temporal grey matter reduction, frontal and insula grey matter enlargement, and corpus callosum enlargement. On the other hand, hippocampal volume and cerebellar hemisphere reductions differed between 22q11DS and higher-IQ controls only. The neuroanatomical substrates for cognitive impairment and psychiatric illness in 22q11DS are at least partially separable. Correlations between regional volumetric abnormalities and age suggest that exaggerated processes of normal adolescent brain maturation contribute to psychosis-risk in 22q11DS, consistent with previous findings in childhood-onset schizophrenia.