What is epilepsy?
Epilepsy is a condition characterized by recurrent seizures. Seizures are abnormal electrical discharges in the brain that temporarily disrupt the normal transmission of messages to the body. They can produce alterations in consciousness, cause odd rhythmic or repetitive movements, jerking or twitching of limbs, and/or can lead to convulsions that contract muscles throughout the body. Sometimes seizures are preceded by epileptic auras. Auras are the heightened sensitivity or unusual perception of sight, sound, smell, taste or touch that warn people of an imminent seizure. They may involve sensations, for example, of a cool breeze or a bright light and may include feelings of numbness or nausea. What happens during a seizure episode depends on which part(s) of the brain are affected. Many people with epilepsy experience similar symptoms with each seizure, but some may have a wide variety of symptoms.
Most seizures last a few seconds to a few minutes. If a person's consciousness is altered or lost, they will frequently not remember what has happened. Those affected may have no after-effects, may have a brief period of confusion, and/or may experience weakness and fatigue that can last for several days. Most seizures do not have a lasting affect on the brain or body, but a loss of consciousness may lead to falls and injuries - especially if the affected person is driving, bathing, cooking, or doing other potentially hazardous activities. Seizures that last longer than five to ten minutes are called status epilepticus and require prompt medical attention. Prolonged seizures, longer than 30 minutes, can increase the risk of permanent damage and can in some cases be fatal.
Not every seizure is considered epilepsy. Those that are due to temporary conditions such as a high fever in an infant, acute meningitis or encephalitis, or alcohol or drug withdrawal are not considered unprovoked seizures. Likewise, not every set of symptoms that looks like a seizure is actually caused by changes in brain electrical activity. Fainting, migraine headaches, narcolepsy, drug use, mental illness, and a variety of other conditions that temporarily alter consciousness or perception may produce some of the same symptoms.
Epilepsy is diagnosed when someone has two or more unprovoked seizures at least 24 hours apart. According to the National Institute of Neurological Disorders and Stroke (NINDS), over 2 million people in the U.S. have experienced an unprovoked seizure or been diagnosed with epilepsy. While epilepsy can affect anyone, children under the age of 2 and adults over 65 are most likely to be affected. The majority of people with epilepsy will respond to treatment, but about 25-30% will continue to have seizures despite treatment.
Any condition that affects the brain has the potential to cause epilepsy. This includes head trauma, abnormal brain development, lack of oxygen during birth, brain tumors, strokes, cerebrovascular disease, toxins such as lead poisoning, infections, neurologic diseases, and metabolic disorders. Some forms of epilepsy run in families and are related to genetic defects. The causes of many cases of epilepsy are unknown; the Centers for Disease Control and Prevention (CDC) states that nearly two-thirds of cases of epilepsy have no underlying cause identified.
Epileptic seizures can be classified as either partial (focal) or generalized. Partial seizures originate from a single location in the brain, while generalized seizures involve both sides of the brain. A few seizures may start as partial seizures and then become secondarily generalized. About 60% of people with epilepsy have partial seizures. For more information about types of seizures, visit the NINDS web page Seizures and Epilepsy: Hope Through Research.