Multiple subpial transection (MST) 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.

Multiple subpial transection (MST) is a newer type of brain surgery used to treat people with epilepsy. The goal of MST surgery is to stop seizures from spreading through the brain while preserving vital functions such as speech, sensation, movement, and memory. MST may be performed alone or in conjunction with other surgeries such as corpus callostomy or temporal lobe resection. The surgery is named for the pia mater, a soft, thin membrane that covers the brain. Multiple shallow cuts (transections) are made just beneath the pia mater, hence the name multiple subpial transection.

Not everyone with intractable epilepsy is a good candidate for MST surgery. MST is most effective in people who experience partial seizures that originate in different parts of the brain, or in parts of the brain that cannot be removed safely. MST has also been found effective in treating Landau-Kleffner syndrome. In order to qualify for an MST, 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 an MST, 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. You and your doctor should decide together whether an MST 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.

If another surgery is also being performed, MST will be performed first. During the MST, 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 and make several shallow transections into the gray, outer layer of your brain just below the pia mater. When the neurosurgeon is finished performing the multiple subpial transections, 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 four to six days after receiving MST 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. 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
MST may help reduce or eliminate seizures, and it may reduce the number or amount of medications you need to take to control your epilepsy.
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Results
MST is effective at improving seizure control in approximately 70 percent of people who receive it. Since MST is a relatively new surgery, long-term effects have not yet been established.

In one study published in 2003, MST was performed in 200 people with intractable epilepsy between 1991 and 2000. One hundred and twenty participants received MST combined with another surgery, and 80 received only MST. Of the 200 participants, 160 were followed for up to eight years. Seizures were controlled completely in 100 people; reduced by at least 75 percent in 32 people, and reduced by more than 50 percent in 20 people. Eight people experienced no change.

Constraints
MST surgery may not be successful in reducing your seizures.

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

MST 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 fatigue, depression, headaches, numbness in your scalp, nausea, and trouble remembering or speaking some words.

Possible complications of MST include swelling in the brain and damage to healthy brain tissue.

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.