Functional hemispherectomy for Epilepsy

Overview

Approximately 20 percent of people with epilepsy cannot adequately control their seizures with anti-epileptic drugs (AEDs). Other people experience serious side effects from AEDs that impact their quality of life. Some of these people may be candidates for surgery.

Functional hemispherectomy is a type of brain surgery used to treat people with epilepsy. The goal of functional hemispherectomy surgery is to remove the seizure focus while preserving as many vital functions as possible.

The brain is divided into left and right halves known as hemispheres. Each hemisphere has four lobes: Frontal, temporal, occipital, and parietal. The two hemispheres are divided by a deep groove. A dense band of nerves called the corpus callosum connects the two halves and allows them to communicate. Seizures can pass from one hemisphere to the other via the corpus callosum. In some people, seizures consistently start in one hemisphere. During a functional hemispherectomy, the neurosurgeon removes a portion of the hemisphere in which the seizures originate and severs the corpus callosum so that seizures cannot pass from one hemisphere to the other.

Not everyone with intractable epilepsy is a good candidate for functional hemispherectomy. Although it is also performed on adults, functional hemispherectomy is considered most effective in children ages 13 or under who experience seizures that originate in one hemisphere. Often the damaged hemisphere functions poorly due to damage, and the child’s development is significantly affected by their epilepsy. In addition, it must be possible to remove the seizure focus with minimal disruption to important brain functions such as memory, personality, senses, and communication. In order to qualify for functional hemispherectomy, you must have tried several different AEDs for significant periods of time. Finally, you and your doctors must agree that the benefits you might gain by undergoing the surgery outweigh the risks of performing the procedure.

What does it involve?
In order to decide whether you are a good candidate for functional hemispherectomy, your neurologist will perform extensive testing. The pre-surgical evaluation tests may include seizure monitoring, magnetic resonance imaging (MRI) scans, positron emission tomography (PET) scans, magnetoencephalography (MEG) tests, Wada tests, and electroencephalography (EEG) monitoring. The EEG monitoring may be performed externally or invasively, using electrodes that are placed inside your skull. Pre-surgical evaluation is very thorough in order to ensure you will receive the maximum possible benefit from the surgery and avoid disruptions of normal brain function as much as possible. You and your doctor should decide together whether a functional hemispherectomy may be right for you. Do not be afraid to ask questions about any aspect of the surgery or recovery.

You will be given instructions to stop eating a few hours or possibly the night before surgery. When you arrive at the hospital, vital signs will be taken, and blood will be drawn for testing. A portion of your head may be shaved. When it is time for the surgery, you will receive an intravenous (IV) line and anesthetic medication to make you sleep.

Functional hemispherectomy surgery can take as long as 12 hours. During the functional hemispherectomy, the neurosurgeon will make an incision in your scalp and retract a flap of skin. The neurosurgeon will then remove a section of your skull in a procedure known as a craniotomy. Next, the neurosurgeon will retract a section of the dura mater, the tough outer covering of the brain. Viewing your brain through a surgical microscope, the neurosurgeon will insert instruments. Most usually, the neurosurgeon will remove the entire temporal lobe of the damaged hemisphere and leave the other lobes intact. The neurosurgeon will carefully separate the two hemispheres and sever the corpus callosum. When the neurosurgeon is finished performing the functional hemispherectomy, they will close the dura mater, fix the skull back in place, and finally close your scalp with staples or stitches.

You can expect to stay in the hospital for five to seven days after receiving functional hemispherectomy surgery. Once you return home, it will take six to eight weeks to recover completely from surgery and resume work, school, or other normal activities. You may need to receive speech, physical, or occupational therapy during your recovery. Your hair will hide the scar when it grows back.

You will likely continue taking your AEDs after surgery until your neurologist establishes how effective the surgery was in controlling your seizures. You may eventually be able to reduce or stop taking your medications. You should never suddenly stop taking an AED. Always consult your neurologist for a plan to taper off gradually in order to avoid withdrawal.

Intended Outcomes
Functional hemispherectomy may help eliminate or significantly reduce seizures, and it may reduce the number or amount of medications you need to take to control your epilepsy. Functional hemispherectomy may improve some children’s ability to function.

Results
Approximately 60 percent of those who undergo functional hemispherectomy become seizure-free. As many as 85 percent gain significant improvement in their condition. Many children with severe epilepsy gain function and improved quality of life after undergoing functional hemispherectomy.

Functional hemispherectomy may be less effective in people with Rasmussen's syndrome and other progressive disorders.

Constraints
Functional hemispherectomy surgery may not be successful in reducing or eliminating your seizures.

Functional hemispherectomy often results in some degree of permanent paralysis of the affected side of the body. The hand on the affected side will lose some function and sensation. Most people who have had a functional hemispherectomy walk with a limp, and some require an ankle brace. There may be changes to personality, cognition, and a loss of peripheral vision.

In rare cases, complications such as hydrocephalus or new seizures may arise months or years after functional hemispherectomy surgery. These complications may be serious or even life-threatening and require emergency medical care.

Functional hemispherectomy surgery can cause pain and swelling, and you will most likely need pain medication for some weeks during recovery. Other temporary side effects may include puffy eyes, fatigue, depression, headaches, numbness in your scalp, nausea, and trouble remembering or speaking some words.

Any surgery carries risks including blood clots, blood loss, infection, breathing problems, reactions to medication, and heart attack or stroke during the surgery.

Possible complications of functional hemispherectomy include swelling in the brain and damage to healthy brain tissue. Even if seizures are eliminated, you may continue to experience auras, the sensations that signal the beginning of a seizure.

It may be challenging to travel to multiple therapy appointments during rehabilitation.

Some people become anxious if they experience a seizure after surgery. A seizure after surgery does not indicate that the surgery was unsuccessful. It may be necessary to examine seizure triggers or adjust medication in order to reestablish control.

Even if surgery is successful at completely controlling seizures, some people have trouble adjusting to life without seizures. Although it is a positive change in many ways, it can create stress and put pressure on interpersonal relationships. Seek support or therapy if you find yourself becoming depressed or anxious due to changes in life after surgery.