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SEIZURES What is a seizure? |
| What is a seizure? A seizure is a sudden alteration of behavior due to a temporary change in the electrical functioning of the brain, especially the cortex. It may be an alteration in behavior, consciousness, movement, perception, and/or sensation. Epilepsy is the tendency to have recurrent seizures. Some characteristics of seizures can include:
Back to top What happens during a seizure? A seizure occurs when the normal electrical balance in the brain is lost. The brain's nerve cells misfire. They either fire when they shouldn't or don't fire when they should. The result is a sudden, brief, uncontrolled burst of abnormal electrical activity in the brain. Seizures are the physical effects of such unusual bursts of electrical energy in the brain.
During a seizure, out-of-sync signals from the brain travel along the nervous system pathway to sensors, such as the nerves that sense light in the eyes or the nerves that flex muscles. These misfiring signals may keep the brain from understanding what the eyes see, so the person stares during a seizure. Or they may affect leg muscle tone and cause a person to fall down. The type of seizure depends on how many cells fire and which area of the brain is involved.
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What are the types of seizures? There are broad two types of seizures: Generalized Tonic Clonic convulsions and Partial seizures. Partial seizures may be Simple or Complex. What are Generalized Tonic Clonic seizures?In generalized seizures, abnormal excessive electricity occurs throughout the whole brain at once, with no apparent focal point of onset or warning beforehand. Generalized seizures alter consciousness. They can be convulsive or non-convulsive. This is the type of convulsive seizure that most people recognize as epilepsy. It used to be called a grand mal seizure, but now is more properly termed tonic clonic: tonic meaning stiffening and clonic meaning jerking. It is a generalized seizure, meaning most of the nerve cells of the brain are firing at the same time so consciousness is lost. The person remains unconscious throughout the seizure. This seizure begins with the tonic phase, in which the body's muscles stiffen. The person will typically let out a cry, which is really the sound of air being forced out through their contracted vocal cords. The stiffening of the body's muscles causes the person to fall to the ground. The back arches, the eyes roll back and the limbs extend. Breathing is difficult because of the stiffened chest muscles, and, with the change in available oxygen, the skin color turns bluish gray. Quickly the clonic phase begins, and the limbs, body and head begin to jerk rhythmically. Saliva builds up in the mouth and the tongue may be bitten. Control of the bladder or bowels may be lost. The person continues convulsing, usually for 1-3 minutes, before the jerking slows and the seizure ends. Often a sigh is emitted as normal breathing begins. After a tonic clonic seizure, the body is limp. The nerve cells in the brain are reacting to their massive misfiring during the seizure. The person is usually confused, sleepy, headachy and irritable for a period of minutes or hours afterwards, and should be allowed to rest until they have fully recovered. Back to top Partial seizures Partial seizures begin in one place in the brain, called the seizure focus, and affect only part of the brain. Depending on where they start and which parts of the brain they involve, partial seizures may or may not alter consciousness or awareness. What are Simple Partial Seizures? Partial seizures that do not alter consciousness are called "simple partial seizures". They used to be known as "focal" seizures because they occur in only a small part of the brain (the focus). The person having the seizure is aware of what is happening. A simple partial seizure usually lasts only a short time. This type of seizure is also known as an "aura" because it often serves as a warning that a bigger seizure will follow. Simple partial seizures vary widely from person to person, depending on where in their brain an individual's seizure focus is located. These seizures consist of an unusual emotion, sensation, or movement. For example, if the abnormal electrical burst occurs in a specific part of the brain responsible for vision, the simple partial seizure will consist of seeing flashing lights. If it is on the brain's sensory strip, the person will experience a tingling arm or leg; on the motor strip, their limb will jerk. Some people experience an overwhelming emotion like fear or dread from yet another part of their brain, or smell an unpleasant odor. Back to top What are Complex Partial Seizures? Complex partial seizures involve deep, central structures of the brain controlling consciousness, so awareness is altered or lost. These used to be known as psychomotor or temporal lobe seizures, because they commonly occur in the brain's temporal or frontal lobes. The brain functions located in these lobes are as complex as the seizures beginning there. A complex partial seizure may begin as a simple partial seizure (like a funny feeling or emotion) before it spreads to areas of the brain controlling awareness, or it may begin without warning with an alteration in consciousness. With this loss of awareness, the person having a complex partial seizure typically stares blankly, and performs automatic, unconsciously repeated movements, such as lip smacking, picking at one's clothes, and wandering around, aimless and confused. These movements are called automatisms. During the seizure, the person's ability to speak, understand and respond is usually affected. This is a very common type of seizure, although the general public does often not recognize it as epilepsy. People having a complex partial seizure are sometimes treated as if they are drunk or high on drugs, and are often mishandled.
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There is no diagnostic test for a seizure or for epilepsy. The doctor's diagnosis is based on a thorough investigation of a first seizure (including any witness observations), a physical examination, family history, and supportive tests such as the EEG, CT Scan, and MRI. The EEG is not foolproof. It can only measure abnormal electrical activity that occurs during the test period. Sometimes, the brain of the person with epilepsy functions perfectly normally during the test. Or the electric patterns that the device is looking for happen too deep in the brain to be picked up by the scalp electrodes of the EEG. When the EEG doesn't find anything unusual, it is common for the patient to get a continuous, 24-hour EEG monitoring in hospital. About 20% of people with epilepsy have normal EEGs, and a small percentage who don't have epilepsy have abnormal ones. Neuroimaging tests are often recommended. CAT or CT scan stands for computerized axial tomography, which uses computer processing and x-rays to make a computer image of the brain in three dimensions. The Magnetic Resonance Imager (MRI) can better define the structures of the brain in three dimensions. All electric currents make magnetic fields, and the MRI measures the strength of these fields. MRS (Magnetic Resonance Spectroscopy) provides information about the brain's functioning and biochemistry which can be used in conjunction with structural MRI or CT images. Functional MRI (fMRI) can look at discrete areas of brain activation. PET (Positron emission tomography) scanning is a highly specialized technique that detects cerebral blood flow and metabolism. Another method, SPECT scanning is technically simpler than PET scanning for determining cerebral blood flow. Back to top
What is the First Aid Procedure for Generalized Convulsive Seizures? When someone is having a tonic clonic or grand mal seizure, you can help by following these steps: 1. Keep Calm. Let the seizure take its course. Do not try to stop the seizure or revive the person. Begin timing the seizure. 2. Protect from further injury if possible. Move hard or sharp objects away, but do not interfere with the person's movements. Place something soft and small such as a sweater under the head, loosen tight clothing, especially at the neck. 3. Do not force anything in the person's mouth. This could cause teeth and jaw damage. The person will not swallow their tongue during a seizure. 4. Roll the person on their side as soon as possible, to allow saliva or other fluids to drain away, helping to clear the airway. DO NOT BE FRIGHTENED if a person having a seizure appears to stop breathing momentarily. 5. On rare occasions, if a seizure goes on longer than 5 minutes, or repeats without full recovery, call for medical help. 6. Afterward, talk gently to the person, be comforting and reassuring and stay with them until they become re-oriented. Back to top What is the First Aid Procedure for Partial Non-Convulsive Seizures? When someone is having a complex partial seizure, you can help by following these steps: 1. Stay With the Person. Do not try to stop the seizure, but let it take its course. The person will be unaware of his or her actions, and may or may not hear you. 2. Gently Guide the Person away from Danger. And move dangerous objects out of the way. 3. Observe Carefully. Note different movements or behaviors. 4. Partial Seizures may Spread to other areas of the Brain. Do not be alarmed if a convulsive seizure follows. 5. Afterward, talk gently to the person, be comforting and reassuring and stay with them until they become re-oriented. Back to top This information was adapted with permission from Epilepsy Toronto is a not-for-profit, registered charity, founded in 1956, dedicated to the promotion of independence and optimal quality of life for all people with epilepsy and their families. Visit their web site at http://www.epilepsytoronto.org/ |
