Of the many neurosurgical interventions that exist, callosotomy is one of the most curious, since it involves dividing the brain, cut the small bridge that connects the left hemisphere with the right: the corpus callosum.
This intervention is key to treating epilepsy, especially when the patient suffers from atonic seizures and the use of anticonvulsant drugs has not helped them to improve their disease.
Throughout this article we will put on the 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 they have undergone a callosotomy.
What is a callosotomy?
The corpus callosum is a structure made up of a band of fibers located deep within the brain., which serve as a bridge connecting the two cerebral hemispheres.
This structure helps both halves of the brain to share information but, also, they have the disadvantage that in case there is a brain disease or psychopathology occurs in one of them, the corpus callosum is the path that causes the symptoms to spread from one hemisphere to another.
One of the brain problems that can spread like this is seizures associated with epilepsy, whose nerve signals that initiate the seizures so characteristic of this disease can travel from one side of the brain to the other through the corpus callosum. To avoid this, callosotomy is used, a surgical procedure in which the corpus callosum is totally or partially sectioned, 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, since they continue to appear on the side of the brain where they originate. Nevertheless, By preventing them from spreading across both hemispheres, seizures become less frequent and less severe, which already implies a marked improvement in the quality of life of the patient.
Types of seizures treated with callosotomy
Callosotomy is a surgical intervention that helps patients suffering from atonic seizures that have not been able to be improved by anticonvulsant drugs.
When a person has an atonic seizure, they suddenly lose muscle strength, fall to the ground, and may lose consciousness. These seizures, also called falling seizures, can be so shocking to the ground that the patient can break bones or suffer concussions. The patient loses muscle tone during the crisis, making him completely flaccid and immobile.
Callosotomy it is not an effective treatment nor is it recommended for people with partial and / or focal seizures. In these cases, the signals that initiate seizures begin in a small region of the brain, a focal point, and uncontrolled brain activity is limited to just one area. Because of this, sectioning the corpus callosum is an unnecessary treatment, since the signals that cause seizures do not spread 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 ensure that this is the best option to treat his case of epilepsy. Among the evaluation techniques that the patient undergoes before being considered a candidate for callosotomy we have:
1. Electroencephalogram (EEG)
Electroencephalography is used to be able to detect brain electrical activity associated with epileptic seizures.
2. Magnetic resonance imaging (MRI)
MRI 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 to identify specific areas of the brain where the crises have their origin.
4. Wada’s test
In the Wada test, a drug is injected into an artery leading to the brain. The objective of this test is find out which side of the patient’s brain controls language and memory.
Currently, this test has been largely replaced by functional magnetic resonance imaging, considered less invasive, although it implies that the evaluated person is asked to do language and memory tasks.
Once the patient has been evaluated with these tests and it is considered that this is the best option to improve their health, the intervention is carried out. The first thing to do before anything else is to inject a powerful anesthetic to induce general anesthesia and fall into a deep sleep. Callosotomy is a very invasive treatment, in which the skull is literally opened (craniotomy) and the brain is searched until the corpus callosum is found in order to section it.
The main steps to be followed in the operation are as follows.
The first part consists of shaving the area of the scalp where the incision will be made.. It is in the selected area where a piece of the skull will be extracted and, immediately afterwards, a section of the dura, the tough membrane that surrounds the brain to protect it, is peeled off, in order to make a “window” that shows us the brain. Once this is done, the brain will be exposed and the neurosurgeon, gently and gently, will separate the two hemispheres of the patient to locate the corpus callosum deep in the brain.
To get the most accurate view of this brain structure, the neurosurgery team uses surgical microscopes to insert the special instruments so that they can cut only the parts that are necessary for the goal of treatment. You cannot simply section parts of the brain, it is necessary to be careful and limit yourself to cutting the nerve fibers just to avoid the propagation of epileptic signals from one side of the hemisphere to the other.
Sometimes a callosotomy is done in two operations. In the first intervention, the neurosurgeon only cuts the front part of the corpus callosum, without completely breaking the bridge that joins both hemispheres. Thanks to this, the epileptic signals are prevented from spreading, but the patient continues to have two hemispheres that share visual information. However, if this first intervention has not been entirely effective and the patient continues to have frequent and severe epileptic seizures, a second intervention will be chosen in which the corpus callosum is definitively sectioned.
Both in the first operation and in the second, if any, the intervention is completed by placing the part of the dura that had been extracted in the corresponding place and, on top of it, the skull bone. Staples are put in place to make sure everything is glued and still.
With the passage of time, the hair will grow back, hiding the surgical scars, the same that will serve as a place where an incision is made again in case a complete callosotomy has to be used.
What happens after the operation?
After the operation, patients undergoing a callosotomy spend between 2 and 4 days in the hospital. They will have to wait between 6 and 8 weeks to be able to return to their normal life, such as going to school or going back to work. Some patients may need more time to recover depending on many factors, including the type of callosotomy that has been performed and whether they have been seen to have any side effects associated with the intervention.
As we have commented, callosotomies do not completely eliminate the possibility of suffering new seizures, but they are expected to reduce their appearance. To counteract the few seizures that may continue to occur, the patient should take anticonvulsant drugs. Likewise, your condition should be monitored after surgery, being aware of whether you suffer from any of the following temporary symptoms:
- Feelings of depression and tiredness
- Memory problems
- Numbness in the incision area
- Speech difficulties
Research shows that callosotomy is an effective way to reduce epileptic seizures when drugs don’t work. About half of the people who have undergone this surgery stop suffering from unconsciousness and falls due to epilepsy in the long term. About one in five people who have had this procedure never have seizures again.
Risks and benefits
As with any surgical procedure, a callosotomy has its risks. Actually, 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 for the patient are greater than the risks of undergoing a callosotomy. However, having serious problems after this procedure is considered relatively rare.
The most common problem that callosotomized patients can present is the well-known interhemispheric disconnection syndrome, which basically consists of the two cerebral hemispheres working and working in a totally uncoordinated and independent way. If the patient closes his eyes and tries to do simple tasks, he will see 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:
- Infection in the incision area: 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 the production of speech.
- Aphasia: problems in understanding speech.
- Stroke: slurred speech, blurred vision, and sudden paralysis of one half of the body.
- Swelling in the brain