Abnormalities of the corpus callosum in nonpsychotic children with chromosome 22q11 deletion syndrome.

Chromosome 22q11 deletion syndrome (22q11DS) is associated with elevated rates of schizophrenia and other psychoses in adulthood. Childhood morphologic brain abnormalities are frequently reported, but the significance of these and their relationship to the development of schizophrenia are unclear. We sought to delineate midline neuroanatomical abnormalities in nonpsychotic children with 22q11DS and their age- and sex-matched controls and compare these to those reported in individuals with schizophrenia. On qualitative analysis, we found a high incidence of midline developmental abnormalities (cavum septum pellucidum, or CSP). On quantitative analysis, the total corpus callosum (CC) area was significantly increased in the patient group and among the subregions, the patients had a significantly larger isthmus. These findings of an increased area of the corpus callosum, specifically the isthmus, have not been reported before in individuals with 22q11DS. We also found a relative lack of the age-related increase in the size of the corpus callosum in the children with 22q11DS. There were no differences in cerebellar vermis measurements between the patient and control groups. Our findings are indicative of frequent midline brain anomalies, including dysgenesis of the corpus callosum, in nonpsychotic children with 22q11DS. Although the increased size of the corpus callosum in our 22q11DS patients is in direct contrast to the decrease seen in schizophrenia, the high frequency of structural midline abnormalities in these nonpsychotic children with 22q11DS is similar to that seen in schizophrenia. Further longitudinal studies on these children will help determine which of these structural abnormalities is/are pertinent to the development of psychosis.