What is epilepsy?
Epilepsy is a neurological condition involving the brain that makes people more susceptible to having recurrent unprovoked seizures. It is one of the most common disorders of the nervous system and affects people of all ages, races and ethnic background. Almost 3 million Americans live with epilepsy.
Anything that interrupts the normal connections between nerve cells in the brain can cause a seizure; this includes a high fever, low blood sugar, alcohol or drug withdrawal, or a brain concussion. Under these circumstances, anyone can have one or more seizures. However, when a person has two or more unprovoked seizures, he or she is considered to have epilepsy. There are many possible causes of epilepsy, including an imbalance of nerve-signaling chemicals called neurotransmitters, tumors, strokes, and brain damage from illness or injury, or some combination of these. In the majority of cases, there may be no detectable cause for epilepsy.
What is a seizure?
The brain is the center that controls and regulates all voluntary and involuntary responses in the body. It consists of nerve cells that normally communicate with each other through electrical activity.
A seizure occurs when part(s) of the brain receives a burst of abnormal electrical signals that temporarily interrupts normal electrical brain function.
What are the different types of seizures?
The type of seizure depends on which part and how much of the brain is affected and what happens during the seizure. The two broad categories of epileptic seizures are generalized seizures (absence, atonic, tonic-clonic, myoclonic) and partial (simple and complex) seizures. Within these categories, there are several different types of seizures, including:
Focal seizuresFocal seizures take place when abnormal electrical brain function occurs in one or more areas of one side of the brain. Focal seizures may also be called partial seizures. With focal seizures, particularly with complex focal seizures, a person may experience an aura before the seizure occurs. The most common aura involves feelings such as deja vu, impending doom, fear, or euphoria. Visual changes, hearing abnormalities, or changes in the sense of smell can also be auras. Two types of focal seizures include:
Simple focal seizuresThe person may show different symptoms depending upon which area of the brain is involved. If the abnormal electrical brain function is in the occipital lobe (the back part of the brain that is involved with vision), sight may be altered, but muscles are more commonly affected. However, more commonly, a person's muscles are affected. The seizure activity is limited to an isolated muscle group, such as the fingers, or to larger muscles in the arms and legs. Consciousness is not lost in this type of seizure. The person may also experience sweating, nausea, or become pale.
Complex focal seizuresThis type of seizure commonly occurs in the temporal lobe of the brain, the area of the brain that controls emotion and memory function. This seizure usually lasts one to two minutes. Consciousness is usually lost during these seizures. Losing consciousness may not mean that a person passes out--sometimes, a person stops being aware of what's going on around him or her. The person may look awake but have a variety of behaviors. These behaviors may range from gagging, lip smacking, running, screaming, crying, and/or laughing. When the person regains consciousness, he or she may complain of being tired or sleepy after the seizure. This is called the postictal period.
Generalized seizuresGeneralized seizures involve both sides of the brain. There is loss of consciousness and a postictal state after the seizure occurs. Types of generalized seizures include the following:
Absence seizures (also called petit mal seizures)These seizures are characterized by a brief altered state of consciousness and staring episodes. Typically, the person's posture is maintained during the seizure. The mouth or face may move or the eyes may blink. The seizure usually lasts no longer than 30 seconds. When the seizure is over, the person may not recall what just occurred and may go on with his/her activities, acting as though nothing happened. These seizures may occur several times a day. This type of seizure is sometimes mistaken for a learning problem or behavioral problem. Absence seizures almost always start between ages 4 to 12 years.
Atonic (also called drop attacks)With atonic seizures, there is a sudden loss of muscle tone and the person may fall from a standing position or suddenly drop his/her head. During the seizure, the person is limp and unresponsive.
Generalized tonic-clonic seizures (GTC or also called grand mal seizures)The classic form of this kind of seizure, which may not occur in every case, is characterized by five distinct phases. The body, arms, and legs will flex (contract), extend (straighten out), and tremor (shake), followed by a clonic period (contraction and relaxation of the muscles) and the postictal period. Not all of these phases may be seen with every one of this type of seizure. During the postictal period, the person may be sleepy, have problems with vision or speech, and may have a bad headache, fatigue, or body aches.
Myoclonic seizuresThis type of seizure refers to quick movements or sudden jerking of a group of muscles. These seizures tend to occur in clusters, meaning that they may occur several times a day, or for several days in a row.
Infantile spasmsThis rare type of seizure disorder occurs in infants before six months of age. There is a high occurrence rate of this seizure when the child is awakening, or when he/she is trying to go to sleep. The infant usually has brief periods of movement of the neck, trunk, or legs that lasts for a few seconds. Infants may have hundreds of these seizures a day. This can be a serious problem, and can have long-term complications.
This type of seizure is associated with fever and is not epilepsy, although a fever may trigger a seizure in a child who has epilepsy. These seizures are more commonly seen in children between six months and five years of age, and there may be a family history of this type of seizure. Febrile seizures that last less than 15 minutes are called "simple," and typically do not have long-term neurological effects. Seizures lasting more than 15 minutes are called "complex" and there may be long-term neurological changes in the child.