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By Melissa Tennen, HealthAtoZ writer
People with epilepsy may go for years with no seizures, thanks to medication. And then, with no explanation, the drugs simply stop working. Some seizure disorders cannot be controlled despite multiple drugs in different combination.
A study from the National Institute of Neurological Disorders and Stroke and Yale University School of Medicine showed that the younger the patient, the longer it may take for the person to develop drug-resistant seizures. Seizures were said to be resistant if at least two anticonvulsant medications did not work.
"This is a completely new field of epilepsy research and we are only just beginning to scratch the surface," said Robert J. DeLorenzo. M.D., Ph.D., M.P.H., professor of neurology, pharmacology and toxicology, biochemistry and molecular biophysics at the Virginia Commonwealth School of Medicine.
"It is important to remember that the absence of clinical seizures does not mean that brain activity has returned to normal, so the underlying biochemistry of the epileptic lesion may continue to change over time, which we know to be true from molecular studies," said Jeffrey L. Noebels, M.D., Ph.D., professor of neurology, neuroscience and molecular genetics in the department of neurology at the Baylor College of Medicine in Houston. "We need medicines that can not only stop seizures, but prevent the changes that lead to drug resistance."
Reasons unknown
These findings set off a cascade of questions among researchers. Who are the people whose seizures won't get under control? How does that happen? Does it happen quickly or slowly? Can you examine a patient's history and tell when the epilepsy can become drug resistant?
In patients who developed seizures before age 5, it took an average of 15 years for seizures to become intractable, according to the study. However, for people who started in their 30s or 40s, the seizures shortly became intractable or within a few years thereafter. The average age of a first seizure was 14.6 years while the average for surgery was 36.7 years.
Researchers already knew that resistance to drugs mostly strikes people who have partial epilepsy, or recurring seizures that happen in part of the brain. These patients may be referred to neurosurgeons to see if they are candidates for surgery. About 60 percent of people with epilepsy have partial seizures. One type is called simple partial seizure when the person remains conscious but may experience unusual feelings or sensations. Another type known as a complex partial seizure, the person may have a change or loss of consciousness. The change in consciousness may be an altered or dreamlike experience.
"Understanding the mechanism of resistance in this type of seizure is paramount since drug failure may lead to the decision to proceed with surgical therapy," says Noebels. Some experts say that epilepsy surgery is one of the most underutilized, safe and effective interventions in medicine. On average, it takes 14 years from the onset of epilepsy to the point where surgical intervention for epilepsy not controlled by medication is performed.
In the U.S. epilepsy affects more than 326,000 children under age 15; more than 90,000 of them have severe seizures that cannot be adequately treated. More than 570,000 adults age 65 and above in the U.S. have the condition.
Types of seizures
Epilepsy is a condition of recurring seizures. In normal brain functioning, millions of tiny electrical charges pass constantly between the nerve cells of the brain and other parts of the body. When a seizure occurs, a signal triggers that something has gone wrong with the electrical system of the brain. The most easily recognized seizure is the convulsion seizure, characterized by shaking movements of the body accompanied by a period decreased mental awareness. Other, less obvious forms of seizures may affect a person's awareness, muscle control or sensory perception.
Researchers know that developing epilepsy is based on what genes say. But not everyone who has the genetic component develops the condition. In all, three percent of Americans will develop epilepsy by age 75. Some causes of acquired epilepsy are brain damage, brain tumors, strokes, lead or other poisoning and lack of oxygen reaching the brain during childbirth. However, in 70 percent of cases, no known cause is ever found.
Epilepsy is first treated with medication. People who have more than one type of seizure may have to take more than one kind of drug, although doctors try to control seizures with one drug if possible. Nearly two dozen drugs exist to treat the condition. Thirty to 40 percent of people with epilepsy are severely affected and continue to have seizures despite treatment.
"In our society, having a seizure once a week or even once a month could be a big problem. You can't drive a car, hold down a job. It's a very serious problem," DeLorenzo says.
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This article was reviewed and updated June 2007.
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