Clinical relevance of sex and age relate variations in corpus callosum morphology

Abstract

Anatomical research of the morphology of the corpus callosum (CC) has provided a baseline for normal development of the CC. Although a large extent of variation amongst individuals has been reported, there are certain asymmetries that are consistently found in the size and shape of the CC on a midsagittal view of the brain. As the CC is the major commissural tract in the brain, it is acceptable to assume that structural variation in the CC may give clues towards the diagnosis of specific diseases. Studies relating alterations in the size and shape of the CC to the diagnosis of disorders have been done in individuals with schizophrenia, bipolar disorder (and depression. Thus, knowledge of CC anatomy in association with sex and age related changes can be helpful in providing a baseline for the diagnosis and progression of a specific disease. Morphological changes with regard to sex and age have been the topic of an extensive amount of research. However, there still remains considerable controversy as some studies report significant differences and others report none. The aim of this study was to provide a detailed description of the anatomy and variations of the corpus callosum morphology in a South African population. A primary data set was compiled using a cadaveric population, and these results were compared to a secondary data set, using a healthy living population. Lastly, the results from both data sets were then compared with a third data set, comprising of a mental disorder population, and results gained from previous studies in order to determine possible diagnoses of certain mental disorders based on CC morphology. In this study, there was no sexual dimorphism observed in the thickness of the genu, splenium and trunk in all three samples. In the cadaver sample there was no difference in the length of the CC. In the mental disorder sample there was no sexual dimorphism in the length of the CC and cerebrum. However, in the cadaver sample there was a significant difference in the length of the cerebrum between the sexes. In the healthy MRI scan there was a statistically significant difference observed in the length of the CC and the length of the cerebrum. It was found that there was no statistically significant difference in the thickness of the genu, trunk, and length of the CC and length of the cerebrum with age in all three samples measured. There was a statistically significant difference observed in the thickness of the splenium in the healthy MRI scan sample in individuals over the age of 60 years of age. This difference was not observed in the cadaver or mental disorder sample. There were no statistically significant differences in the various CC parameters measured in the various mental disorders measured. With the exception of two parameters, no differences in measurements were observed between the cadaver and healthy MRI sample. The two exceptions were the thickness of the trunk and the length of the cerebrum. Therefore, with the exception of the above mentioned cases, measurements between cadavers and living samples can be used interchangeably. Thus, the concerns about shrinkage in cadaver studies are negligible. However, when comparing the cadaver and healthy MRI scan sample with the mental disorder CT scan sample there was a statistically significant difference observed in every CC parameter measured. Thus, there is a rather noticeable difference in the anatomical structure of the CC in individuals suffering from mental disorders. Data on normal CC morphology is under represented in the South African population. Observations of variations from normal CC morphology can be used as an indicator for the possibility of a mental disorder.