The corpus callosum is the band of nerves that connect the two hemispheres of the brain. It enables the two hemispheres to communicate with each other and share information. However, in the case of epilepsy, it also allows seizure activity to travel from one hemisphere to the other. Corpus callosotomy is a surgical procedure that involves cutting all or part of the corpus callosum, disabling communication between the two halves of the brain, and preventing seizures from spreading from one side to another.
Seizures are not totally eliminated after this procedure, but they are less severe because they cannot spread to the opposite side of the brain.
Indications
Corpus callosotomy is considered when:
- seizures have persisted, despite trying medication (monotherapy and polytherapy) for at least two years
- pre-surgical evaluation demonstrates that it is not possible to identify a single epileptogenic region.
Corpus callosotomy is most helpful for atonic seizures, also known as "drop attacks." These seizures are often seen in Lennox-Gastaut syndrome. Even when corpus callosotomy does not result in complete seizure freedom, eliminating these "drop attacks" can result in far fewer falls and injuries.
Before surgery
A complete and comprehensive pre-surgical evaluation is essential to ensure that the child would not benefit from resection of a single epileptogenic region.
The surgeon and the team will explain the surgery to you and discuss all related issues. They will instruct you on any specific steps to take prior to the operation.
They will also discuss post-operative symptoms, any intensive care and rehabilitation that will be required, and possible on-going deficits and care.
Surgery
The operation will take about six hours and will require a general anaesthetic.
A portion of your child's head will be shaved. Part of the scalp and bone will be removed and the dura membrane will be peeled back to expose the corpus callosum. Some or all of the corpus callosum will be cut through.
In some cases, the corpus callosotomy is done in two stages. The first time, only the front two-thirds of the corpus callosum is cut, leaving the back section intact so the hemispheres can share some information. If seizures persist, then a second operation is done to cut the remainder. Your child's neurologist and neurosurgeon can discuss whether your child would benefit most from a complete or partial callosotomy.
After the operation, the bone will be replaced and the scalp will be sutured closed. Your child will spend a few hours in the recovery room until they come out of anaesthesia and one or two days in the intensive care unit, followed by about a week at the hospital.
Possible side effects after surgery
Side effects of the surgery depend on the extent of the surgery and the areas of the brain that are affected. Temporary side effects of this surgery, which should disappear on their own in a few weeks, are scalp numbness, nausea, fatigue, depression, headaches, difficulties with memory and speech and auras (feelings that signal the start of a seizure). Rarely, some of these effects may persist. The surgeon and neurologist can talk to you about the side effects they expect for your child.
With a complete callosotomy, there is a risk of a complication called disconnection syndrome. This means that information does not travel between the two hemispheres of the brain. For instance, if a child sees an object only with their left eye, the right hemisphere will see the object but the information will not be transferred to the left hemisphere. If the child's left hemisphere is dominant for language, they will not be able to name the object, even though they recognize it. The risk of this syndrome is greater in older patients with normal intellectual development. The syndrome does not usually cause problems for the patient, because information comes in through both eyes.
Your child may benefit from doing exercise therapy to improve any physical weakness or loss of coordination they may have. In the hospital, physical and occupational therapists will help your child and may show you some exercises. They may also need speech therapy if their speech has been affected.
Once your child is at home, they may need to continue using the services of a physical or occupational therapist in the community. The treatment team will discuss this with you and may be able to help you find a therapist.
The hair should grow back and most children are able to return to normal activities and school two or three months after surgery.
Anti-epileptic drugs should be continued after the surgery. As always, any change in dosage should be made under advice and monitoring of your child's doctor. Sometimes the drugs can be stopped after a few seizure-free years.
What can you expect from the surgery?
Every child is different. Depending on the nature of your child's seizures and the location of the epileptogenic region, surgery may result in complete seizure control or "partial" seizure control with less need for medication. There may also be some chance that the surgery will not improve things. Talk to your child's doctor about what you and your child can realistically expect as a result of the surgery.
Complications and risks
Every surgical procedure has related risks, including infection, bleeding, cerebral edema, and allergy to or complications from anaesthetic. Other risks from corpus callosotomy include:
- a possibility that partial seizures may still persist and may even increase
- lack of co-ordination and other specific risks and side effects because of a lack of communication between the two hemispheres.
Your child's doctor will discuss the risks of this procedure with you in detail.