A morphological study of the shape of the corpus callosum in normal, schizophrenic and bipolar patients

Abstract

Abnormalities in the morphology of the corpus callosum have been found to be involved in cognitive impairments or abnormal behaviour in patients with mental disorders such as schizophrenia and bipolar disorder. The present study investigated morphological shape differences of the corpus callosum in a large cohort of 223 participants between normal, schizophrenic and bipolar patients on MRI scans, CT scans and cadaver samples. Healthy samples were compared to a mental disorder population sample to determine morphological shapes variations associated with schizophrenia and bipolar disorder. Landmark‐based methodology was used to contour the corpus callosum shape that served as standard positions to allow for radial and thickness partitioning in order to determine shape variations within the specific localised anatomical sections of the corpus callosum. Shape analysis was performed using Ordinary Procrustes averaging and superimposing landmarks to define an average landmark position for the specific regions of the corpus callosum. No significant global shape differences were found between the different mental disorders. Schizophrenia and bipolar shapes differed mostly in the genu‐rostrum, posterior body, isthmus and splenium. Sample group comparisons yielded significant differences between all groups and global measurement parameters and in various sub‐regions. The findings of the present study suggest that the corpus callosum in schizophrenia and bipolar differs significantly compared to healthy controls, specifically in the anterior body and isthmus for schizophrenia and only in the isthmus for bipolar disorder. Shape changes in these regions may possibly, in part, be responsible for the symptoms and cognitive impairments observed in schizophrenia and bipolar disorder.

The Genetic Architecture of the Human Corpus Callosum and its Subregions

“…Most CC fibers connect corresponding left and right cortical regions of the brain, with the organization, development of axonal elongation, and myelination of callosal fibers being correlated with the rostro-caudal (front-to-back) distribution of functional areas 5,6 . Regional alterations in CC shape are easily assessed with neuroimaging studies, which have found local callosal abnormalities in complex neurodevelopmental and neuropsychiatric disorders [6][7][8][9][10][11] , such as lower anterior volumes in autism 12 and lower posterior thickness in bipolar disorder 13 . Twin studies show up to 66% heritability for CC area 14,15 , and previous single-cohort studies of genetic influences on CC volume and its relationship to neuropsychiatric disorders have found heritability estimates between 22-39% 16,17 .…”