Callosotomy: what is it, phases, usefulness and associated risks?

Let's see what callosotomy, a surgical procedure used in cases of epilepsy, consists of.

Of the many neurosurgical interventions that exist, callosotomy is one of the most curious, since it involves dividing the brain, cutting the small bridge that connects the left hemisphere to the right hemisphere.It involves dividing the brain, cutting the small bridge that connects the left and right hemispheres: the corpus callosum.

This intervention is key to treat epilepsy, especially when the patient suffers atonic seizures and the use of Anticonvulsant drugs has not helped him to improve his disease.

Throughout this article we will put on our neurosurgeon's gown and discover how this peculiar intervention is performed, what benefits and risks it entails and how it can improve the patient's life once he has undergone a callosotomy.

What is a callosotomy?

The corpus callosum is a structure made up of a band of fibers located deep in the brain, which serve as a bridge connecting the two cerebral hemispheres.which serve as a bridge connecting the two cerebral hemispheres.

This structure helps both halves of the brain to share information, but it also has the disadvantage that in case of any brain disease or psychopathology in either of them, the corpus callosum is the pathway that causes symptoms to spread from one hemisphere to the other.

One of the brain problems that can spread in this way are the seizures associated with epilepsy, whose nerve signals that initiate the epileptic seizures so characteristic of the brain. seizures so characteristic of this disease can travel back and forth through the corpus callosum from one side of the brain to the other.. To avoid this, a callosotomy is performed, a surgical procedure in which the corpus callosum is totally or partially severed, that is, cutting the bridge that connects the two hemispheres and preventing the seizures from spreading to the other side.

Generally, this intervention does not prevent seizures from continuing to appear, since they continue to appear on the side of the brain where they originate. However, by preventing seizures from spreading to both hemispheres, seizures become less frequent and less severe, which in itself means that seizures are less frequent and less severe.This in itself implies a noticeable improvement in the patient's quality of life.

Types of seizures treated with callosotomy.

Callosotomy is a surgical intervention that helps patients suffering from atonic seizures that could not be ameliorated by anticonvulsant drugs..

When a person has an atonic seizure, he or she suddenly loses muscle strength, falls to the ground and may lose consciousness. These seizures, also called drop seizures, can be so jarring to the ground that the patient may break bones or suffer concussions. The patient loses muscle tone during the seizure, making him/her totally limp and immobile.

Callosotomy is not an effective treatment and is not recommended for people with partial and/or focal seizures.. In these cases, the signals that initiate seizures start in a small region of the brain, a focal point, and the uncontrolled brain activity is limited to only one area. Because of this, sectioning the corpus callosum is an unnecessary treatment, since there is no propagation of the seizure-provoking signals from one hemisphere of the brain to another.

Previous medical evaluations

Before performing a callosotomy it is necessary for the patient to be evaluated with different diagnostic tests to make sure that this is the best option to treat their case of epilepsy.. Among the evaluation techniques by which the patient is submitted before being considered as a candidate for callosotomy we have:

1. Electroencephalogram (EEG)

Electroencephalography is used to be able to detect the cerebral electrical activity associated with epileptic seizures.

2. Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging is used to evaluate structural changes in the brain that may be the cause of seizures..

3. Positron Emission Tomography (PET)

Positron Emission Tomography is used for identify the specific areas of the brain where seizures where the crises have their origin.

4. Wada test

In the Wada test, a drug is injected into an artery leading to the brain. The purpose of this test is to to find out which side of the patient's brain controls language and memory..

This test has now largely been replaced by functional MRI, which is considered less invasive, although it involves asking the person being tested to perform language and memory tasks.

Surgical intervention

Once the patient has been evaluated with these tests and it is considered that this is the best option to improve his or her health, the intervention proceeds. The first thing that is done first of all is to inject a powerful anesthetic to induce general anesthesia and that it falls in a deep sleep. Callosotomy is a very invasive treatment, in which the skull is literally opened (craniotomy) and the brain is probed until the corpus callosum is found and sectioned.

The main steps involved in the operation are as follows.

The first part consists of shaving the area of the scalp where the incision is to be made.. It is in the selected area where a piece of the skull will be removed and then a section of the dura mater, the hard membrane that surrounds the brain to protect it, is detached in order to make a "window" that shows the brain. Once this is done, the brain will be exposed and the neurosurgeon, in a soft and gentle manner, will move the patient's two hemispheres apart to locate the corpus callosum in the depths of the brain.

In order to have the most accurate view possible of this brain structure, the neurosurgical team uses surgical microscopes to insert special instruments to cut only the parts that are necessary for the goal of the treatment. It is not possible to cut out parts of the brain without further intervention, it is necessary to be careful and to limit oneself to cutting just enough nerve fibers to avoid the spread of epileptic signals from one side of the hemisphere to the other.

Callosotomy is sometimes performed in two operations.. In the first operation, the neurosurgeon only cuts the front part of the corpus callosum, without completely breaking the bridge linking the two hemispheres. This prevents the spread of epileptic signals but the patient continues to have two hemispheres sharing visual information. However, if this first operation is not completely effective and the patient continues to have frequent and severe epileptic seizures, a second operation will be performed in which the corpus callosum is definitively severed.

In both the first and the second operation, if any, the operation is completed by placing the part of the dura mater that was removed in its proper place and, on top of it, the skull bone. To make sure that everything is well glued and still in place, staples are placed.

With the passage of time, the hair will grow back, hiding the surgical scars, the same ones that will serve as a place to make an incision again in case a complete callosotomy has to be performed.

What happens after the operation?

After surgery, callosotomy patients spend 2 to 4 days in the hospital.. They will have to wait 6 to 8 weeks before they can return to normal life, such as going to school or returning to work. Some patients may need more time to recover depending on many factors, including the type of callosotomy performed and whether they have been seen to have any side effects associated with the procedure.

As mentioned above, callosotomies do not completely eliminate the possibility of further seizures, but they are expected to reduce their occurrence. To counteract the few seizures that may continue to occur, the patient should take anticonvulsant drugs.. The patient's condition should also be monitored after surgery for any of the following temporary symptoms:

• Fatigue
• Feelings of depression and tiredness
• Headaches
• Memory problems
• Nausea
• Numbness at the incision site
• Speech difficulties

Research shows that callosotomy is an effective way to reduce epileptic seizures when drugs do not work.. About half of the people who have had this surgery stop having long-term epilepsy-related blackouts and falls. Approximately one in five people who have undergone this procedure never have seizures again.

Risks and benefits.

As with any surgical procedure, callosotomy has its risks. In fact, all surgical treatments for epilepsy present several risks, since they are neurosurgery and intervening on the brain involves very delicate operations. Therefore, before performing them, it should be assessed whether the benefits to the patient outweigh the risks of undergoing callosotomy. However, serious problems following callosotomy are considered to be relatively uncommon.

The most common problem that may occur in callosotomized patients is the well-known interhemispheric disconnection syndrome, which basically consists of the two interhemispheric bones of the foot being disconnected.This basically consists of the two cerebral hemispheres functioning and working in a totally uncoordinated and independent manner. If the patient closes his eyes and tries to do simple tasks, he will find that he cannot because the two sides of his brain will not want to cooperate, making movements in conflict with each other.

Other potential problems associated with callosotomy are:

• Fever
• Infection at the incision site: red, tender skin and yellowish pus.
• Loss of coordination or balance problems.
• Very severe headaches and nausea.
• More partial seizures on one side of the brain.
• Apraxia: problems in speech production.
• Aphasia: problems in understanding speech.
• Strokes: slurred speech, blurred vision and sudden paralysis of half of the body.
• Swelling in the brain.