Isthmus of the corpus callosum – An anatomical investigation

Abstract

Introduction: The corpus callosum, a principal commissural fibre-bundle of the brain, connects the two cerebral hemispheres, facilitating interhemispheric communication, cognitive and emotional processes. The anatomical definition of the isthmus of the corpus callosum remains unclear in literature with limited studies focusing on this region. This research addresses this gap by providing a detailed anatomical description of the isthmus of the corpus callosum in a South African cadaveric sample. Methods: Digital photographs of thirty embalmed cadaver brains were analysed and measurements of the corpus callosum and isthmus were taken, as seen on a midsagittal section. Results: The results revealed no significant differences in isthmus measurements when comparing the sex of the cadavers. The average length of the isthmus accounted for approximately 16.66 % of the total length of the corpus callosum. The isthmus constituted approximately 17.92 % of the corpus callosum surface area. Females tend to have a larger isthmus relative to the size of their corpus callosum. The prevalence of a posterior notch on the superior border of the corpus callosum was found to be approximately 46.66 % in the studied sample, with males showing a slightly higher prevalence. Conclusion: Since the isthmus constituted almost 20 % of the total surface area of the corpus callosum, as seen on midsagittal sections, it should be acknowledged as a fifth part. It should further be included in the undergraduate neuroanatomy curriculum and textbooks, which is currently lacking this information. This research recommends expanding the sample size, encompassing diverse demographics, employing fresh cadavers, and utilize three-dimensional imaging to understand the isthmus of the corpus callosum and its relevance to neuropsychiatric conditions and brain morphology.

Keywords

• Cerebral hemisphere
• Commissural fibers
• Corpus callosum
• Isthmus
• Posterior notch