Callosotomy: What It Is, Phases, Usefulness And Associated Risks
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 to improve their disease.
Throughout this article we will put on the neurosurgeon’s coat 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.
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.
This structure helps both halves of the brain share information, but it also has the drawback that if 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 in this way are the seizures associated with epilepsy, whose nervous signals that initiate The epileptic 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 seizures from spreading to the other side.
Generally, this intervention does not prevent seizures from continuing to occur, since they continue to appear on the side of the brain where they originate. However, By preventing them from spreading to both hemispheres, seizures become less frequent and less severe which in itself implies a notable improvement in the patient’s quality of life.
Types of seizures treated with callosotomy
Callosotomy is a surgical intervention that helps patients who suffer from atonic seizures that have not been 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 drop seizures, can be so impactful against 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.
The callosotomy It is not an effective treatment nor is it recommended for people who suffer from partial and/or focal seizures In these cases, the signals that initiate epileptic seizures begin in a small region of the brain, a focal point, and the uncontrolled brain activity is limited to just one area. Because of this, sectioning the corpus callosum is an unnecessary treatment, since the propagation of the signals that cause seizures from one hemisphere of the brain to the other does not occur.
Previous medical evaluations
Before performing a callosotomy It is necessary that the patient be evaluated with different diagnostic tests to ensure that this is the best option to treat their case of epilepsy Among the evaluation techniques that the patient undergoes before being considered as a candidate for callosotomy we have:
1. Electroencephalogram (EEG)
Electroencephalography is used 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 causing seizures
3. Positron emission tomography (PET)
Positron emission tomography is used to identify specific areas of the brain where crises have their origin.
4. Wada test
In the Wada test, medication 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.
Surgical intervention
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 proceeds. The first thing that is done before anything else is to inject a powerful anesthetic to be able 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 to be sectioned.
The main steps followed in the operation are the following.
The first part consists of depilating 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 removed and, immediately afterwards, a section of the dura mater, the hard membrane that surrounds the brain to protect it, is removed in order to make a “window” that shows us the brain. Once this is done, the brain will be exposed and the neurosurgeon will gently and gently separate the patient’s two hemispheres to locate the corpus callosum deep in the brain.
To have as precise a view as possible of this brain structure, the neurosurgery team uses surgical microscopes in order to insert special instruments so that only the parts that are necessary for the treatment goal can be cut. You cannot simply cut off parts of the brain; it is necessary to be careful and limit yourself to cutting just the right nerve fibers to prevent the spread 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 unites both hemispheres. Thanks to this, 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 completely 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.
In both the first operation and the second, if any, the intervention is completed by placing the part of the dura mater that had been removed in its corresponding place and, on top of it, the skull bone. To ensure that everything is well glued and securely in place, staples are placed.
Over time, the hair will grow back, hiding the surgical scars, which will serve as a place to make an incision again in case a complete callosotomy has to be resorted to.
What happens after the operation?
After the operation, patients who undergo 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 lives, 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 reported to have any side effects associated with the procedure.
As we have mentioned, callosotomies do not completely eliminate the possibility of suffering new seizures, but it is expected to reduce their occurrence. To counteract the few seizures that may continue to occur, the patient must take anticonvulsant drugs Likewise, your condition should be monitored after surgery, paying attention to whether you suffer from any of the following temporary symptoms:
Research shows that Callosotomy is an effective way to reduce epileptic seizures when drugs do not work About half of people who have undergone this surgical intervention stop suffering from loss of consciousness and falls due to epilepsy in the long term. About one in five people who have undergone this procedure never have seizures again.
Related article: “The 8 types of speech disorders”
Risks and benefits
As with any surgical intervention, 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 must be assessed whether the benefits for the patient are greater than the risks involved in undergoing a callosotomy. However, it is considered that suffering serious problems after this intervention is relatively uncommon.
The most common problem that callosotomized patients can present is the well-known interhemispheric disconnection syndrome, which basically consists of the two cerebral hemispheres functioning and working in a completely 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:
Fever
Infection in the incision area: red, soft skin and yellowish pus.
Loss of coordination or balance problems.
Very intense 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 the body.
