Surgery for Seizures and Split Brain Syndrome

Split-brain surgery, or corpus calloscotomy, is a radical way of reducing the frequency and severity of epileptic seizures. It involves cutting the corpus callosum, the region of the brain that connects the left and right hemispheres. When a split-brain surgery is performed, the left and right hemispheres do not communicate as effectively as before. This impairment of communication can result in split-brain syndrome, a condition where the disconnection of the hemispheres affects behavior.

Epilepsy

• Epilepsy is the occurrence of sporadic electrical storms in the brain, known as seizures. A seizure occurs when abnormal neuron firing spreads to neighboring neurons. In the case of partial seizures the abnormal neuron firing originates from a specific area of the brain and doesn't spread further. In the most severe cases, the seizure transfers from one side of the brain to the other, which leads to a generalized seizure involving the whole brain.

Symptoms and Treatment

• The severity of symptoms can vary greatly depending on the type of seizure. Symptoms of seizure vary from staring spells and temporary loss of consciousness to the violent convulsions characteristic of generalized seizures. Medication can usually control and substantially reduce the frequency of seizures. However, in some patients the symptoms are so severe that only split-brain surgery can alleviate them.

Split-Brain Surgery

• The most common form of split brain surgery is a partial callosotomy, which removes only two-thirds of the corpus callosum. If this does not reduce the number or severity of seizures, patients can choose to undergo a complete callosotomy, which removes the remaining one-third of neurons. Cutting the corpus callosum normally prevents seizures from moving from one side of the brain to the other. Partial seizures can still occur, but they are easier to control with medication.

Split-Brain Syndrome

• Michael Gazzaniga and Roger W. Sperry, the first to study split brain in humans, found that most patients who have undergone a complete callosotomy suffer temporarily from split-brain syndrome. In patients with split-brain syndrome the right hemisphere, which controls the left hand and foot, acts independently of the left hemisphere and the conscious intentions of the person. This gives rise to a kind of split personality, in which the left hemisphere issues demands that reflect conscious intentions, whereas the right hemisphere issues conflicting demands that reflect hidden preferences.

The Uncontrollable Right Hemisphere

• Sperry and Gazzaniga's split-brain experiments are now legendary. One of their patients, Paul S, had a developed language center in both hemispheres. This allowed the researchers to interview each hemisphere. When they asked the right side what Paul S wanted to be, he replied "an automobile racer," and when they asked the left, he replied "a draftsman." Another patient tried to pull up his pants with the right hand and pull them down with the left. Another time, this same patient's left hand tried to strike his wife as his right hand grabbed it to stop it.