Seizures (SEE-zhers) occur when the electrical patterns of the brain are interrupted by powerful, rapid bursts of electrical energy. A seizure may cause a person to lose consciousness, to fall down, to jerk or convulse, or simply to blank out for a few seconds. Infection, injury or medical problems can cause a seizure. Epilepsy is a disease of the nervous system characterized by recurring seizures.
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As part of his sixth grade study of self-awareness, Eric was assigned to draw the frames of a film that would show the world as he saw it. Teachers were puzzled by what Eric drew. One frame showed him pouring milk, the next frame was completely black, and the next frame showed spilled milk. In another sequence, Eric drew a teacher calling on him to answer a math problem, followed by another black frame, and then a picture of the teacher complaining that Eric was not paying attention. The teachers realized that Eric's project did show the world as he saw it. The mysterious black frames were blackouts. Doctors determined that Eric had absence seizures, a type of seizure that causes a brief loss of consciousness. Medication successfully controlled Eric's seizures.
All the students in Carol's art class were preparing work for an art show when Carol stood up and began walking around the room. Looking like she was in a trance, Carol smacked her lips and tugged at the sleeve of her dress. About two minutes later, Carol became aware of her surroundings, only to discover that her classmates were laughing at her strange behavior. Embarrassed, she ran from the room. Carol had experienced a complex partial seizure.
* neurons are nerve cells. Most neurons have extensions called axons and dendrites through which they send and receive signals from other neurons.
What Is a Seizure?
Whether a person is sleeping or awake, millions of tiny electrical charges pass between neurons * in the brain and to all parts of body. These cells "fire," or transmit electrical impulses, in an orderly and controlled manner. Seizures occur when overactive nerve cells send out powerful, rapid electrical charges that disrupt the brain's normal function. The disruption can temporarily affect how a person behaves, moves, thinks, or feels.
Symptoms of a seizure can include combinations of the following:
- twitching and tingling in part of the body (for example, fingers and toes)
- muscle spasms spreading to arms and legs
- intense feeling of fear or of familiarity (sometimes called deja vu)
- a peculiar sensation, sometimes called an aura, immediately before the seizure (for example, seeing a flashing light or sensing strange odors)
- loss of consciousness.
How Do Seizures Differ?
There are two kinds of seizure disorders: an isolated seizure that occurs only once, and epilepsy (EP-i-lep-see). Epileptic seizures occur more than once, and they occur over a period of time. In both epilepsy and isolated seizures, the seizure may have different symptoms or characteristics depending on where it begins in the brain and how the electrical discharge spreads across the brain. Seizures can be generalized or partial.
Generalized seizures affect nerve cells throughout the cerebral cortex (the cauliflower-like outer portion of the brain), or all of the brain. Generalized seizures often are hereditary, which means they run in families. They may also be caused by imbalances in a person's kidney or liver function, or in their blood sugar.
The most common generalized seizures are:
- Generalized tonic-clonic seizure (formerly called grand mal seizure): In the tonic phase of this seizure, people often lose consciousness, drop to the ground, and emit a loud cry as air is forced over their vocal cords. In the clonic phase, body muscles contract all at once or in a series of shorter rhythmic contractions, causing thrashing motions. Usually, this kind of seizure lasts for about one or two minutes and is followed by a period of relaxation, sleepiness, and possibly a headache.
- Absence seizure (formerly called petit mal seizure): Loss of consciousness in this seizure is often so brief (usually 10 to 30 seconds) that a person does not even change positions. The person may display a blank stare, rapid blinking, or chewing movements. Facial or eyelid muscles may jerk rhythmically. Absence seizures may be inherited and usually are seen for the first time in children between the ages of 6 and 12.
- Infantile spasms: This type of seizure occurs before age 4 and may cause a child to suddenly flex the arms, thrust the trunk forward, and extend the legs. The seizure lasts only a few seconds, but can recur several times a day.
- Atonic seizures: Also seen primarily in children, these seizures cause a complete loss of muscle tone and consciousness, which means they pose a serious risk of injury due to falling.
- Myoclonic seizures: Brief seizures characterized by quick jerking movements of one limb or several limbs. The person experiencing the seizure does not lose consciousness.
- Febrile seizures: These seizures occur in infancy or childhood and cause a child to lose consciousness and convulse. The seizures are accompanied by a high fever and they are described as either simple or complex. Simple febrile seizures account for about 85 percent of febrile seizures. They occur once in 24 hours and last less than 15 minutes. Complex febrile seizures last more than 15 minutes or occur more than twice in 24 hours.
Partial seizures affect nerve cells contained within one region of the cerebral cortex. Types of partial seizures include:
- Simple partial: The seizure-related brain messages remain very localized, and the patient is awake and alert. Symptoms vary depending on what area of the brain is involved. They may include jerking movements in one part of the body, emotional symptoms such as unexplained fear, an experience of peculiar smells, or nausea.
- Complex partial: A person loses awareness of surroundings and is unresponsive or only partially responsive. There may be a blank stare, chewing movements, repeated swallowing, or other random activity. After the seizure, the person has no memory of the experience. In some cases, the person may become confused, begin to fumble, to wander, or to repeat inappropriate words or phrases.
What Causes A Seizure?
A seizure generally is easy to recognize, but finding the cause can be extremely difficult. Doctors begin with a thorough physical examination. They try to determine if the person has experienced other seizures or has a family history of seizures. Physicians also want to know if the patient has experienced an aura * , because that can help establish the location in the brain of the seizure. They also will note the person's age and the nature of the movements the person made during the seizure.
An electroencephalogram (e-LEK-tro-en-SEF-a-lo-gram), commonly known as an EEG, records electric currents in the brain and can track abnormal electrical activity. Doctors may also look for structural brain abnormalities using other types of scans, including computerized tomography (CT) and magnetic resonance imaging (MRI). In some research centers, positron emission tomography (PET) is used to identify areas of the brain that are producing seizures.
A lumbar puncture, sometimes called a spinal tap, can detect infection. The procedure requires that a physician carefully insert a thin needle between two vertebrae (bones) in the patient's spine and draw out a small amount of cerebrospinal fluid (CSF). The fluid is analyzed for the presence of bacterial or viral infections, tumors, or blood disorders that might provide a clue to the cause of the seizure.
* aura is a warning sensation that precedes a seizure or other neuro-logic disorder.
Seizures are associated with the following diseases and conditions:
- Epilepsy, a disorder of the nervous system characterized by seizures that occur more than once and over a period of time.
- Head trauma that damages the brain.
- Loss of oxygen caused by birth trauma, carbon monoxide poisoning, or near drowning.
- Brain infections, such as meningitis or encephalitis.
- Brain tumor.
- Toxic (poisonous) agents, including drug abuse or ingestion of poisons such as lead, alcohol, or strychnine.
- Withdrawal from alcohol and drugs.
- Metabolic imbalances such as hypoglycemia (very low blood sugar), uremia (kidney failure), or liver problems.
- Eclampsia or toxemia, which may occur during pregnancy and is characterized by high blood pressure, protein in the urine, and fluid retention.
It is important to remain calm and not to panic when someone has a seizure. An adult usually will ask if the person has epilepsy. If the person is unable to communicate, an adult will check for a medical identification bracelet or tag that carries information about the underlying cause of the seizure.
Orrin, Devinsky, M.D. A Guide to Understanding and Living With Epilepsy. Philadelphia: F.A. Davis, 1994. An easy-to-read guide with a glossary of terms and antiepileptic drugs.
Wilner, Andrew N. Epilepsy: 199 Answers. A Doctor Responds to His Patients' Questions. New York: Demos Vermande, 1996.
The Epilepsy Foundation, 4351 Garden Drive, Landover, MD 20785. Formerly
the Epilepsy Foundation of America, this national organization offers
information on seizures and epilepsy. The website provides general
information on diagnosis and treatment, plus web links and a chat room