Corpus callosotomy is a surgical procedure that disconnects the cerebral hemisphere

Cerebral hemisphere

A cerebral hemisphere is one of the two regions of the eutherian brain that are delineated by the median plane, . The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres has an outer layer of grey matter called the cerebral cortex that is...

s, resulting in a condition called split-brain

Split-brain

Split-brain is a lay term to describe the result when the corpus callosum connecting the two hemispheres of the brain is severed to some degree. The surgical operation to produce this condition is called corpus callosotomy and is usually used as a last resort to treat otherwise intractable epilepsy...

.

Most modern callosotomies involve only the anterior portion of the corpus callosum

Corpus callosum

The corpus callosum , also known as the colossal commissure, is a wide, flat bundle of neural fibers beneath the cortex in the eutherian brain at the longitudinal fissure. It connects the left and right cerebral hemispheres and facilitates interhemispheric communication...

, reflecting the fact that the frontal lobe

Frontal lobe

The frontal lobe is an area in the brain of humans and other mammals, located at the front of each cerebral hemisphere and positioned anterior to the parietal lobe and superior and anterior to the temporal lobes...

 and temporal lobe

Temporal lobe

The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....

 are the lobes of the brain

Lobes of the brain

Brain lobes were originally a purely anatomical classification, but have been shown also to be related to different brain functions. The telencephalon , the largest portion of the human brain, is divided into lobes, but so is the cerebellum...

 most commonly involved in the genesis of seizure

Seizure

An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...

s. The deficits from this modified procedure are milder; side-effects have not been found in some patients (although it is very unlikely that none exist).

The corpus callosum is usually severed in order to stop epileptic seizures. Once the corpus callosum is cut, the brain has much more difficulty sending messages between the hemispheres. Although the corpus callosum is the largest white matter

White matter

White matter is one of the two components of the central nervous system and consists mostly of myelinated axons. White matter tissue of the freshly cut brain appears pinkish white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries. Its white color is due to...

 tract connecting the hemispheres, some limited interhemispheric communication is still possible via the anterior commissure

Anterior commissure

The anterior commissure is a bundle of nerve fibers , connecting the two cerebral hemispheres across the midline, and placed in front of the columns of the fornix...

 and posterior commissure

Posterior commissure

The posterior commissure is a rounded band of white fibers crossing the middle line on the dorsal aspect of the upper end of the cerebral aqueduct. It is important in the bilateral pupillary light reflex....

. When tested in particular situations, it is obvious that information transfer between the hemispheres is reduced.

External links

• Detail on the procedure from epilepsy.com
• Encyclopedia of Surgery: Corpus callosotomy