Corpus callosum abnormalities in pediatric bipolar disorder

The corpus callosum (CC) is a midline white matter brain region that is important in interhemispheric communication and coordination. CC abnormalities are associated with a variety of psychiatric conditions, including increased vulnerability for psychotic illness, stressful early-life experiences, marijuana use, attention-deficit/hyperactivity disorder, obsessive-compulsive disorder, borderline personality disorder, dementia, schizophrenia and bipolar disorder. CC abnormalities in bipolar disorder have been identified in both pediatric and adult populations. In adults, a consistent finding has been a reduction in CC size, as well as abnormal axonal orientation or structure. Axonal abnormalities have also been noted in pediatric populations, but overall CC size reductions have not thus far been demonstrated. Furthermore, there are unique gender differences in the expression of CC abnormalities in pediatric populations, possibly related to androgen changes during puberty. The protean number of conditions in which the CC is involved is reflective of its central role in normal brain function and its potential as an early marker of neuropathology in psychiatric illness. Specifically, in bipolar disorder it has the potential to be useful as an early preclinical marker of disease or disease risk.