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The corpus callosum, also known as the great commissure of the brain, is the most important commissure connecting both hemispheres of the brain. It is made of white matter, tissue that forms the central nervous system. The corpus callosum is located roughly in the middle of the skull surface, in the longitudinal valley of the brain. Its development occurs in utero, in the first trimester after pregnancy.
How the corpus callosum is built
The corpus callosum is a fairly late evolutionary acquisition. Experts estimate that it emerged only during the development of placental mammals. It is located where the soft meninges (covering the neocortex of the brain) meet and where the bundle of axons connecting the two hemispheres of the brain is extremely dense. The corpus callosum is not just a commissure in the human brain. There is also an anterior and posterior commissary. Their moment of formation in the history of the human species is much earlier than in the case of the corpus callosum.
The corpus callosum is a commissure, usually 7-10 cm long. The division of the corpus callosum into several subparts includes:
- the trunk of the corpus callosum, which is the central part of this organ,
- a flap, located in the rear part, connecting with the trunk,
- knee, i.e. the place near the commissure where the corpus callosum bends downwards,
- beak,
- fore plate, ending the corpus callosum.
The corpus callosum is covered with a layer of gray matter called a thread. There are numerous longitudinal, medial and lateral stripes under its surface. Under the corpus callosum, there is a vault that forms the triple ceiling of the third chamber. Commissural fibers depart from the corpus callosum, which, running sideways above the lateral ventricles of the brain, create the so-called radiance of the corpus callosum. The corpus callosum has an impact on the general structure of the brain, especially the course of furrows and folds on its surface.
The function of the corpus callosum
The function of the corpus callosum was not discovered until the mid-50s. Currently, it is estimated that the structure of this organ consists of 200 million axonal projections.
The main function of the corpus callosum is related to its position. The corpus callosum participates in the exchange of information that travels from one hemisphere of the brain to the other. It integrates the work between the hemispheres, which, despite the partially homologous structure and structure, include various centers: motor, visual, somatic-sensory, speech and others.
Diseases of the corpus callosum
The most common diseases affecting the corpus callosum include hypoplasia of the corpus callosum. The structure of the corpus callosum develops during fetal life and after birth, even up to the age of 12. Only at this age is it possible to speak of a fully developed corpus callosum. The hypoplasia of the corpus callosum is an example of a disease in which the normal development of this organ is disturbed. Most often, its proper structure is not fully developed, for example due to an insufficient number of nerve connections that form it.
Agenesis of the corpus callosum is a disease involving the occurrence of significant disturbances within the structure of the corpus callosum. Agenesis can take many forms: complete or partial. In the case of the first, the corpus callosum does not develop at all. In partial agenesis, the developed corpus callosum is incomplete.
Some cases of agenesis of the corpus callosum have a genetic basis and are associated with the occurrence of specific mutations. Moreover, various other disorders in the fetal stage of the development of the central nervous system and its structures can lead to the development of agenesis. The development of agenesis may also be influenced by: rubella in a pregnant woman, CMV infection, alcohol consumption during pregnancy.
The most common symptoms of agenesis of the corpus callosum include:
- seizures
- feeding difficulties
- hypotension,
- slow pace of development,
- difficulties with empathizing with other people’s emotional states, reduced empathy, problems with establishing social relationships,
- problems in solving logical problems, focusing attention,
- hydrocephalus,
- dysmorphic defects.
In order to find out the agenesis of the corpus callosum, an ultrasound examination is performed in the womb. Most often, diagnosis is not made until the postpartum period.