Options in seizure management: the vagus nerve stimulator--experiences to date: Part 1: an introduction to seizure disorders and existing therapies. (Special Report).
Seizures can occur for many different reasons or with no known cause. A seizure that occurs without a medical cause is known as an "idiopathic" seizure. Seizures can also occur as isolated events resulting from fever, illness, head injury, or lack of oxygen. Idiopathic seizures that occur more than once are defined as a seizure disorder, or epilepsy.
To arrive at a diagnosis of epilepsy, a physician will obtain a detailed history of the individual and symptoms before, during, and after a seizure. A physical examination may be performed, and blood and body fluids analyzed. An electroencephalogram (EEG), which measures electric activity in the brain and is used as a diagnostic tool, will be performed. Sometimes, the person being examined may wear a monitor to allow continuous EEG recording, and have his or her physical activity monitored as well. Imaging tests such as CT and MRI scans show the brain's internal structure and may reveal any brain abnormalities that would not otherwise be detected. The information yielded by each test dictates which others will be performed.
THE IMPACT ON QUALITY OF LIFE
A seizure disorder can have a devastating effect on an individual's life. In January 2001, The Centers for Disease Control and Prevention (CDC) issued a report based on a Texas study of adults with or without epilepsy, ages 18 and older. Of a population of 3,355 people, those with epilepsy reported more physically and mentally unhealthy days, more days of pain, depression, anxiety, and insufficient sleep, and fewer days of vitality than those without epilepsy.
According to the Epilepsy Foundation, children with seizure disorders are also affected. These children may feel isolated from other students at school, and they are often victims of shunning or teasing brought on by their classmates fear and lack of understanding about seizures. Low self-esteem and low academic achievement are more common in children with seizure disorders.
The goal of all seizure management therapies is to prevent further seizures with a minimum of side effects. There are four treatment modalities available for the management of seizure disorders. These are drug therapy, surgery, the ketogenic diet, and the vagus nerve stimulator. The physician usually discusses all available treatment options with the individual and his or her family before deciding which course is the best to pursue.
Most seizure medications are taken orally and are often used in combinations. The most commonly prescribed are:
* valproic acid
* A rectal gel form of diazepam is available for use in children to stop prolonged seizures.
* divalproex sodium
Different drugs control different types of seizures. A medication is prescribed depending on what type of seizure(s) an individual experiences. If a particular drug treatment appears ineffective, the dosage may be increased, another drug may be added, or a different combination of drugs may be tried. Because people have different responses and sensitivities to drugs, it takes time to find the right drug or combination of drugs that best control an individual's seizures.
Dr. Paul Levisohn, assistant professor of pediatrics and neurology at the University of Colorado Health Sciences Center, and medical director of the Children's Epilepsy Center at the Children's Hospital in Denver, Colorado, relates the difficulty of truly defining at what point an individual's seizures become refractory to drug treatment: "In adults and adolescents, studies suggest that after three drugs used in adequate doses have failed, there is a small chance that further drugs will provide full seizure control. Thus, many of us will define intractability after three drugs have failed to control seizures."
Drugs that are taken for extremely short periods and discontinued because of side effects are often not included in the criteria for intractability. Dr. Levisohn says, "I don't count medications which aren't tolerated due to side effects and have been discontinued without an adequate trial of treatment."
If seizures are refractory, surgery is another option for managing them. Depending on the area of the brain affected, epilepsy surgery can be performed to remove the area of the brain that is responsible for seizure activity, or to interrupt the seizure impulses and stop them from spreading.
Surgeries can range from the fairly localized lobectomy, which removes a portion of the lobe of the brain in which seizures occur, to the hemispherectomy, which removes all or most of an entire hemisphere of the brain. A surgery called a corpus callosotomy either partially or completely severs the corpus callosum--the nerve fibers that connect the brain's hemispheres.
Side effects of surgery range from minor to severe. In a lobectomy, there is usually little or no residual damage to the brain. A more radical surgery such as a hemispherectomy can result in weakness and partial paralysis on the side of the body opposite that of the hemisphere removed, and loss of peripheral vision.
Dr. Angus A Wilfong is assistant professor of pediatrics and neurology at Baylor College of Medicine and medical director of the Clinical Epilepsy Program at Texas Children's Hospital. He notes that recovery from brain surgery may not be as difficult for young candidates as it is for adults. "In children, the brain is plastic. If they lose a skill because of surgery, there is a good chance they may re-learn it using another part of the brain. This is not so for adults."
The rate of success for epilepsy surgery depends on the type of surgery performed and can often be predicted. Successful epilepsy surgery may completely stop seizures or reduce their frequency and severity. It is important to note that not everyone with refractory epilepsy is a candidate for surgery. If seizures are occurring in an area that is near a part of the brain responsible for essential functions, surgery will most likely not be an option.
THE KETOGENIC DIET
The ketogenic diet is used mainly in children whose seizures are not adequately controlled with drug therapy and for whom surgery is not recommended. This high-fat, low-carbohydrate, restricted calorie diet changes the way the body obtains energy, by forcing it to burn fat. The diet requires the combined efforts of family and medical professionals to ensure that the diet is strictly followed and that any side effects are monitored.
Adherence to the ketogenic diet may be difficult for some individuals, but research indicates that with compliance, it can be effective about 30% of the time, either stopping or lessening the frequency of seizures, and allowing a reduction in the amount or dosage of medications.
THE VAGUS NERVE STIMULATOR
For individuals with seizures that are not controlled with drugs, or who are experiencing adverse effects with drug therapy, and for whom surgery is not possible, the vagus nerve stimulator (VNS) is a nonpharmacologic option for short- and long-term seizure management.
Vagus nerve stimulation using the NeuroCybernetic Prosthesis[R] System was approved by the FDA in 1997 for use as adjunctive therapy in refractory seizures in adults and children 12 years of age and older. Today, in the US and Europe, more than 10,000 individuals of all ages and with a variety of seizure types have undergone VNS implantation.
VNS consists of a generator the size of a stopwatch that is surgically implanted in the chest wall. The generator is connected to a nerve stimulation lead wire that runs under the skin and is wrapped around the vagus nerve in the neck. The vagus nerve is one of the primary communication lines from the body's major organs to the brain. It was chosen because it has few if any pain fibers, over 80% of signals applied to the vagus nerve are sent to the brain, and the stimulation lead wire can be attached in a procedure that does not involve brain surgery.
After implantation, the generator is programmed to deliver the appropriate dose of stimulation at pre-set intervals. One dose commonly used by physicians is 30 seconds of stimulation every 5 minutes. Additional stimulation can be self-administered or administered by a caregiver simply by placing, or swiping, a magnet (a component of the VNS system) over the area of the chest where the generator is implanted. This magnetic activation of the generator will stop or shorten a seizure 75% of the time.
With younger children, people who are with the child on a daily basis (parents, teachers, and caregivers) can be taught to swipe the magnet in front of the child's chest and stop or shorten a seizure.
BENEFITS OF PROGRAMMED STIMULATION
VNS can shorten the duration and reduce the frequency of seizures, improve the post-seizure period, improve alertness, memory, and cognition, and necessitate fewer emergency room visits. Often, people who had to take multiple drugs at high doses to control seizures are able to take fewer drugs at much lower doses or, in some cases, stop medication entirely. This reduces or eliminates the issue of side effects from drug therapy.
In his experience, Dr. Wilfong has noticed that VNS works for all types of seizures, not just partial seizures. It is difficult to predict how someone will respond to VNS, however. Studies have shown that about 1/3 of patients experience major improvement in seizure control; 1/3 experience some improvement; and 1/3 continue to have seizures as before. Dr. Wilfong adds that with VNS, improvement is not always immediate--it can take months before a response is seen. Then, he says, "If you respond, you will continue to respond. With VNS, efficacy actually increases for about the first two years and then stays the same. It does not lose effectiveness over time."
SIDE EFFECTS WITH VNS
The most common side effects occur when the generator is stimulating the vagus nerve. They include hoarseness, cough, tickling in the throat, and changes in voice tone until the stimulation cycle ends. The magnet can be used to shut off the generator when side effects are a concern--for example, during public speaking. An individual can hold the magnet over the chest to stop stimulation. When the magnet is removed, the VNS resumes its programmed stimulation cycle.
CONCERNS BEFORE IMPLANTATION
Dr. Syed Hosain, assistant professor of pediatrics and neurology at Weill Cornell Medical College in New York City and director of the Pediatric Epilepsy Program, talked about the importance of patient selection for the procedure. "People's expectations are very important. Vagus nerve stimulation is not a cure, and it is usually used in addition to medication." However, he adds, "It works."
Dr. Levisohn agrees on the importance of discussing the family's and patient's expected outcomes, their goals regarding epilepsy, and clarifying realistic expectations.
Many people are hesitant to have the implantation surgery because they believe it somehow involves the brain or is actually brain surgery. When he encounters apprehension of the procedure by the patient or the family, Dr. Hosain makes sure that they have the opportunity to speak to others who have already undergone VNS implantation. This, more than a physician's explanation of the surgical procedure, eases anxiety for both the patient and the family.
VNS is the first new approach to the treatment of epilepsy in more than 100 years. Although it is a recent advance, it has had a profound impact on the lives of many people with refractory seizure disorders. Part 2 of this series will feature in-depth discussions of experiences with VNS from both patient and physician perspectives, and the effect of VNS on quality of life issues in different populations.
GENERALIZED SEIZURES FALL INTO SEVERAL CATEGORIES:
When the electrical disturbance affects the entire brain, it is termed a generalized seizure. If only part of the brain is affected, it is called a partial seizure. Sometimes, a seizure begins as a partial seizure and then spreads to the entire brain as a secondary generalized seizure.
GENERALIZED TONIC CLONIC (OR GRAND MAL)--Often begins with a sudden cry, fall, and bodily stiffness followed by jerking movements of the arms, legs, and head. Breathing can be be shallow or stop completely. Skin may turn bluish. Seizures normally last a minute or two, after which normal breathing resumes. The individual may be confused or tired afterwards and fall asleep.
ABSENCE SEIZURE--Begins and ends suddenly, usually lasting a few seconds, and occurs frequently. It involves a blank stare, which may be accompanied by upward rolling of the eyes, rapid blinking, or chewing movements. The individual quickly returns to full alertness once the seizure stops. Absence seizures are often mistaken for daydreaming.
ATONIC SEIZURE--Also called drop seizures. A sudden loss of muscle tone causes the individual to collapse. Sometimes there is only a sudden drop of the head. A few seconds to a minute later there is a full return to consciousness. These seizures can cause injuries because of the fall.
MYOCLONIC SEIZURE--These involve a quick, sudden jerk. They may be mild and affect one part of the body or severe enough to throw an individual to the floor. Can occur singularly or in clusters.
PARTIAL SEIZURES CAN OCCUR AS SIMPLE OR COMPLEX SEIZURES
SIMPLE PARTIAL SEIZURE--Affects movement and sensation, but not consciousness. It may involve jerking movements that affect one side of the body and may progress to a generalized seizure. Partial seizures that affect sensations may cause things to look, sound, taste, smell, or feel different. May also cause stomach pain, nausea, or sudden fear or anger.
COMPLEX PARTIAL SEIZURE--Alters consciousness, and the individual is not aware during the seizure. It may begin with a blank stare, chewing movements, and repeated motions. The individual may seem dazed, and may perform various acts (picking up or putting down objects, picking at clothes, or trying to run away). This type of seizure lasts for a few minutes, but the individual may remain confused and uneasy afterwards. The individual has no memory of the seizure.
ABBIE, AGE 18
"ABBIE ENJOYS LIFE EACH AND EVERY DAY."
Abbie developed encephalitis at age 6. After that, she had about three complex partial seizures and 11 complex partial/secondary generalized seizures per month. She required special care for one to three days following these seizures. Abbie had been on a total of 11 different seizure medications, each proving to be less helpful than the last.
Since the VNS implant, Abbie is much more alert and her speech has improved. She interacts with her family and has made friends outside her family. Abbie has a job and is earning money.
The vagus nerve stimulator has given us a sense of control. When you use the magnet and see the seizure stop, it is just awesome!
Abbie talks about the magnet and has learned to use it, which gives her great self-satisfaction. Abbie enjoys life each and every day.
Number of seizures:
Before VNS: 14/month
After VNS: 7/month, can often be stopped with magnet
Type of seizures:
Before VNS: complex partial secondary generalization
After VNS: complex partial secondary generalization
Before VNS: 11 medications
After VNS: lamotrigine, carbamazepine
SURGICAL IMPLANTATION PROCEDURE
Unlike other types of epilepsy surgery, surgical implantation of the VNS does not involve the brain. The generator and lead are implanted in the chest and neck in a procedures that involves:
* 45 minutes to 1 hour of surgery
* A small incision on the side of the neck for the lead wire
* A small chest incision in the area of the armpit for the generator
* A 6-hour to overnight hospital stay
BRAD, AGE 26
"THERE HAS BEEN NO SEIZURE ACTIVITY"
In September of 1994, I had my first seizures. Then, pretty much like clockwork, I would experience a grand mal seizure once every two months. I never knew what would bring them on. The first two seizures I lost consciousness, and that was very scary, especially for the people around me. It really shook them up.
After my sixth seizure I began taking 700 mg of gabapentin and 750 mg of carbamazepine. Yet I continued feeling very tired and "shaky." I just wanted to get rid of the drugs. That's when my doctor suggested VNS. I said "Let's go for it." I had the VNS implant in February of 1996.
Immediately my outlook was more positive and I felt more confident. I had been having 6 to 12 seizures a day and they decreased to 2 a day. Then, within the next month, the seizures decreased to 2 a week.
Since March of 1997, there has been no seizure activity and no dizziness like before. I feel more rested. Before I would sleep 10 to 12 hours a day and still feel exhausted. I now can sleep 6 to 8 hours and feel good. Also, because of my seizures, I had given up coaching because I could not work a full-time job. Last year, I began teaching full-time and coaching part-time.
This year, I will be teaching and coaching full-time. I am also teaching driver's education, where before I could not even drive!
Number of seizures:
Before VNS: 12/day
After VNS: one since March 1997
Types of seizures:
Before VNS: generalized tonic clonic
After VNS: generalized tonic clonic
Before VNS: gabapentin, carbamazepine
After VNS: carbamazepine
ANSWERS TO QUESTIONS ABOUT VNS
1. DO SMALL ELECTRICAL APPLIANCES, CELLULAR PHONES, OR METAL DETECTORS AFFECT VNS?
According to the manufacturer, properly operating microwave ovens, toasters, hair dryers, and electrical appliances should not affect the pulse generator. Based on testing to date, cellular phones do not affect the pulse generator. Metal detectors at airports and other places should not affect the pulse generator.
2. WHAT ARE THE HAZARDS, IF ANY, OF OTHER KINDS OF MEDICAL TREATMENT OR TESTS WHEN SOMEONE HAS A VNS IMPLANT?
The manufacturer says that most routine procedures, such as having an ultrasound or an x-ray, should not affect VNS, although it is always a good idea to make sure that the people doing the procedures are aware that a patient has a VNS implant. Healthcare personnel providing any kind of treatment should be told when someone is also being treated with VNS. If someone with VNS is going to have an MRI scan, special precautions should be taken. These should be discussed with the doctor in advance and the technicians giving the MRI should also be aware of the VNS implant.
3. DOES VNS CAUSE SLEEP DISTURBANCES?
There have been reports that some people with VNS may have pauses in regular breathing (sleep apnea) and other sleep interruptions when the device turns on during sleep. These have often occurred in individuals with pre-existing sleep disturbances. If the patient or family members notice this effect, the doctor should be told. Decreasing some of the stimulation settings can alleviate the apnea.
4. IF THE MAGNET DOESN'T PREVENT A SEIZURE, DOES THAT MEAN VNS ISN'T WORKING PROPERLY?
Possibly. Or it could mean that the settings may need to be changed. Someone with a VNS implant who has previously been able to prevent seizures by using the magnet should tell the doctor if it appears to have stopped working. On the other hand the extra stimulation that the magnet produces will not stop a seizure for everyone.
5. DOES THE IMPLANT HAVE TO BE REPLACED AFTER A PERIOD OF TIME?
The device can last up to 12 years, depending on the model, the stimulation settings used, and how the electrodes and vagus nerve work together over time. The battery may have to be replaced after 6 years.
6. WHERE CAN I GET MORE INFORMATION ABOUT VNS?
Check with your doctor, or contact the Epilepsy Foundation at (800) 332-1000. You can visit the Epilepsy Foundation Web site at http://www.epilepsyfoundation.org. The Epilepsy Foundation in your community, or your doctor, may be able to put you in touch with other VNS users. Information is also available from the manufacturer's Web site at http://www.cyberonics.com.
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|Publication:||The Exceptional Parent|
|Date:||Aug 1, 2001|
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