Corpus callosum

Anatomy and parts

The corpus callosum is divided into four parts: rostrum, genu, body/trunk and splenium

• The rostrum is continuous with the lamina terminalis and connects the orbital surfaces of the frontal lobes.
• The genu is the bend of the anterior corpus callosum and the forceps minor is a tract that projects fibres from the genu to connect the medial and lateral surfaces of the frontal lobes.
• The body forms the long central section and its fibres pass through the corona radiata to reach the surface of the hemispheres.
• The splenium tapers away at the posterior section, with the forceps major projecting fibres from the splenium to connect the two occipital lobes.

White matter fibres projecting from the body and fibres from the splenium not included in the forceps major are known as the tapetum, and run along the entire lateral occipital and temporal horns of the lateral ventricle. Broadly speaking there are two types of connections: homotopic and heterotopic.

Homotopic connections link similar regions from the left and right sides of the brain, while heterotopic connections connect dissimilar areas of the left and right sides of the brain.

Learn everything about the corpus callosum and surrounding structures with our study unit or take our quiz to see what you already know:

Functions

The main function of the corpus callosum is the communication between the two hemispheres; the different parts of the corpus callosum connect similar areas of each hemisphere. Eg the rostrum and genu connect the frontal lobes of the left and the right hemisphere, the body and the splenium connect the temporal lobes of the hemispheres as well as the occipital lobes. In this way the similar areas are interconnected and communicate in a way that there is a harmonization of their functions. 

Besides its importance in communication, the corpus callosum is hypothesized to play a primary role in cognition. Emerging evidence suggests that weakened integrity of the callosum contributes to a decline in cognitive function in aging adults. On the flip side, increased callosal thickness in typical childhood development correlates with intelligence, processing speed, and problem-solving abilities. 

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Surrounding structures

Superior to the body of the corpus callosum lies the interhemispheric fissure which the falx cerebri runs within, as well as the anterior cerebral vessels. The superior aspect of the corpus callosum is covered with a thin layer of glial tissue under the pia mater, known as the indusium griseum, over which run on either side of the midline one or two strips of grey matter, i.e. the longitudinal striae.

The cingulate gyrus is a component of the limbic system and lies superolateral to the corpus callosum. The callosal sulcus separates the two structures. The anterior part of the corpus callosum (rostrum, genu, body) is attached inferiorly to the fornix by the septum pellucidum while the splenium is attached inferiorly to the crura and the commissure of the fornix.

If you would like to challenge yourself even further, try out our quiz on the structures seen on the medial view of the brain.

Blood supply

The blood supply to the corpus callosum is rich and strengthened by anastomoses, which means the area is rarely affected by infarcts.

The vast majority of the blood supply to the corpus callosum comes from long and short callosal branches of the pericallosal artery (the distal continuation of the anterior cerebral artery), whose course follows the outer border of the corpus callosum, first in the subcallosal area, then in the callosal sulcus or in the cingulate sulcus.

The posterior pericallosal (splenial) artery usually is a branch of the posterior cerebral artery but its origin is variable. It bifurcates into an inferior and a superior branch, which supply the inferior and superior part of the splenium respectively. The superior branch usually anastomoses with the pericallosal artery.

In the majority of patients, the corpus callosum also gets blood supply from the anterior communicating artery via either the median callosal or the subcallosal artery. The subcallosal artery supplies the hypothalamus in part, but also supplies the rostrum and genu of the corpus callosum.

The median callosal artery is very similar to the subcallosal artery, but it runs further in order to reach the body of the corpus callosum.

You can test yourself on the arteries of the brain with our quiz.