Epilepsy occurs when clusters of nerve cells fire simultaneously in an abnormal pattern.
Mutations in genes that help guide brain cells to their correct positions during development can result in epilepsy. In this MRI scan of an epileptic patient’s brain, mutation of an X-linked gene has resulted in faulty migration of a band of neurons (arrow).
This activity then spreads to part or all of the brain, triggering seizures that can range in intensity from mild disorientation to full-body convulsions with loss of consciousness.
- A single seizure is not enough for a diagnosis of epilepsy. Rather, a person must suffer two or more seizures over an extended period.
- Epilepsy affects 3 to 4 million Americans. Worldwide, it strikes 50 to 100 million, many of whom lack access to basic treatment.
- Many people with epilepsy cannot drive or participate in everyday activities because of the risk of a sudden seizure.
- Some people with epilepsy die suddenly, for unknown reasons; extended seizures also can be fatal.
- Epilepsy causes $15.5 billion in direct and indirect costs each year in the United States alone.
A devastating and costly disease, epilepsy has been known since ancient times. Historians theorize it struck figures as varied as Socrates, Julius Caesar, Joan of Arc, Napoleon Bonaparte, and Fyodor Dostoevsky.
Fortunately, research supported by the National Institutes of Health and other funding agencies is paving the way to new diagnostics and more effective treatments for epilepsy.
A Matter of Control
Epilepsy is a complex disease, with some 40 distinct subtypes. Infections, tumors, brain injuries, and other lesions can trigger epilepsy, and scientists can often directly detect such seizure-causing abnormalities using brain scanning technology. Other types of seizures are triggered primarily by genetic risk factors, although sometimes no apparent cause can be found. The condition can occur at any age, but appears more frequently in children and the elderly.
Most cases of epilepsy respond well to medication. More than 20 different drugs are available, half of which were developed in the past two decades. These act in a variety of ways, which include reducing the activity of sodium channels involved in nerve cell firing or altering the behavior of neurotransmitters that allow communication between brain cells. For some drugs, the mechanism remains unknown. Because medications can have serious side effects, some trial and error is usually needed to find the best treatment. Many patients eventually go into remission, suffering no further seizures even when weaned off medication.
In 30 to 40 percent of patients, however, drugs don’t work or lead to intolerable side effects. In those cases, surgery can often reduce or eliminate seizures, if doctors can detect the tissue where seizures begin and remove it without affecting vital brain functions. Other treatment options include electrical stimulation of the vagus nerve, a large nerve leading into the brain, or a specific type of diet known as a ketogenic diet. Overall, 60 to 70 percent of people with epilepsy can eventually be "cured" of seizures.