Callosotomy: what it is, phases, utility and associated risks

Among the many neurosurgical procedures, callosotomy is one of the most curious, as it involves dividing the brain., cut the small bridge that connects the left hemisphere to the right: the corpus callosum.

This intervention is essential for treating epilepsy, especially when the patient suffers from atonic seizures and the use of anticonvulsant drugs has failed to improve the disease.

Throughout this article, we’ll put on the neurosurgeon’s gown and find out how this particular procedure is performed, what benefits and risks it entails, and how it can improve the patient’s life after they have had 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.

    This structure helps the two halves of the brain to share information, but it also has the disadvantage that if there is a brain disease or psychopathology in one of them, the corpus callosum is this pathway that causes symptoms to occur. ‘extend from one hemisphere to another.

    One of the brain problems that can spread in this way are the seizures associated with epilepsy, the nerve signals of which trigger the epileptic seizures so characteristic of this disease can travel from one side of the brain to the other through the corpus callosum. To prevent this, callosotomy, 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 seizures from spreading from the hemispheres is used. other side.

    Usually, this intervention does not prevent seizures from continuing to appear, as they continue to appear next to the brain where they originated. However, by preventing them from spreading to both hemispheres, seizures become less frequent and less severe, which in itself implies a marked improvement in the patient’s quality of life.

      Types of seizures treated with callosotomy

      The callosotomy is a surgical procedure that helps patients with atonic seizures that could not be improved with anticonvulsant drugs.

      When a person suffers from a sluggish seizure, they suddenly lose muscle strength, fall to the ground, and may pass out. These seizures, also known as falls, can be so shocking to the ground that the patient can break bones or suffer concussions. The patient loses muscle tone during the seizure, so he is completely limp 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 signs that trigger epileptic seizures start in a small region of the brain, a focal point, and uncontrolled brain activity is limited to a single area. Therefore, severing the corpus callosum is unnecessary treatment, as it does not allow the propagation of signals that cause seizures from one hemisphere of the brain to another.

        Prior medical assessments

        Before having a callosotomy the patient should be evaluated with different diagnostic tests to make sure this is the best option for treating your case of epilepsy. Among the assessment techniques that the patient undergoes before being considered a candidate for callosotomy, there are:

        1. Electroencephalogram (EEG)

        Electroencephalography is used to detect electrical activity in the brain associated with epileptic seizures.

          2. Magnetic resonance imaging (MRI)

          MRI is used to assess 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 crises have their origin.

          4. The test of Wada

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

          Currently, this test has largely been replaced by functional MRI, which is considered less invasive, although it does involve the person being assessed being asked to perform language and memory tasks.

          Surgical intervention

          Once the patient has been assessed with these tests and this is considered the best option for improving their health, the procedure is performed. The first thing to do is to inject a strong 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 to sever it.

          The main steps followed in the operation are as follows.

          The first part is to shave the area of ​​the scalp where the incision will be made. It is in the chosen area that a piece of skull will be extracted and then a section of the duramare is removed, the hard membrane that surrounds the brain to protect it, 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 pull both hemispheres away from the patient to locate the corpus callosum deep in the brain.

          To get as precise a view as possible of this brain structure, the neurosurgery team uses surgical microscopes to insert special instruments so that only the parts needed at the end of treatment can be cut. You can’t cut parts of the brain without more or less, you have to be careful and just cut the right nerve fibers to prevent the spread of epileptic signals from one side of the hemisphere to the other.

          Sometimes the callosotomy is performed in two operations. During the first operation, the neurosurgeon cuts only the front of the corpus callosum, without completely breaking the bridge that connects the two hemispheres. Thanks to this, the epileptic signals are prevented from spreading, but the patient continues to have two hemispheres that share visual information. However, in the event that this first intervention was not 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 permanently severed.

          In the first and second operation, if necessary, the operation is completed by the placement of the part of the dura that had been extracted and, above all, the bone of the skull. To make sure everything stays snug and still in place, staples are placed in place.

          Over time, the hair will grow back, hiding the surgical scars, the same ones that will serve as the place to make an incision again in case you need to have a full callosotomy.

            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 resume a 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 that was performed and whether they experienced any side effects associated with the procedure.

            As we mentioned, callosotomies do not completely eliminate the possibility of new seizures, but they are expected to reduce their occurrence. To counter the few seizures that may continue to occur, the patient should take anticonvulsants.. Your condition should also be monitored after surgery, depending on whether or not you have any of the following temporary symptoms:

            • Tired
            • Feelings of depression and fatigue
            • Headache
            • Problems memory
            • Nausea
            • Numbness in the area of ​​the incision
            • Speech difficulties

            Research shows that callosotomy is an effective way to reduce seizures when medications don’t work. About half of the people who have had this surgery stop suffering from unconsciousness and fall into long-term epilepsy. About one in five people who have had this procedure never have a seizure again.

              Risks and Benefits

              As with any surgical procedure, callosotomy involves risks. Indeed, all surgical treatments for epilepsy present various risks, because it is neurosurgery and intervening on the brain involves very delicate operations. Therefore, before performing them, it is necessary to assess whether the benefits for the patient outweigh the risks associated with performing a callosotomy. However, it is considered that suffering from serious problems after this procedure is relatively rare.

              The most common problem that callosotomy patients can experience is the well-known interhemispheric disconnection syndrome., which basically consists of the two cerebral hemispheres functioning and working in a totally uncoordinated and independent manner. If the patient closes their eyes and tries to do simple tasks, you will find that they cannot because both sides of the brain will not want to cooperate, making movements in conflicting ways with each other.

              Other potential problems associated with callosotomy are:

              • Fever
              • Infection in the area of ​​the incision: red, soft, yellowish pus.
              • Loss of coordination or imbalance problems.
              • Very intense headache and nausea.
              • No more partial seizures on one side of the brain.
              • Apraxia: speech production problems.

              • Aphasia: problems with understanding speech.

              • Strokes: dragged speech, blurred vision, and sudden paralysis of half the body.
              • Swelling in the brain.

              Bibliographical references

              • Schachter SC (2009). Convulsive disorders. Med Clin North America. 93 (2): pages 342 – 351
              • Hofer, S .; Frahm, J. (2006). Revised topography of the human corpus callosum: full fiber tractography using diffusion tensor magnetic resonance imaging. NeuroImage. 32 (3): pages 989 – 994.
              • Mantellina, DL; Nariño, D .; Acevedo, JC; Berbeo, ME and Fox, OF (2011) Callosotomy in the treatment of resistant epilepsy. Bogota Medical University, 52 (4): p. 431-439.
              • Witelson, S. (1985). The brain connection: the corpus callosum is wider on the left. Science. 229 (4714): p. 665 – 668.

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