Epilepsy is a group of disorders characterized by recurrent seizures. In epilepsy, brain cells (neurons) create abnormal electricity that causes seizures or jerking movements. In some cases, seizures cause a loss of consciousness, a period of confusion, a staring spell, or muscle spasms.
A single seizure is not considered epilepsy. Individuals with epilepsy have repeated episodes of seizures. Different forms of epilepsy are either secondary to a particular brain abnormality or neurological disorder, or are said to be idiopathic (without any clear cause).
Normally, nerve transmission in the brain occurs in an orderly fashion, allowing a smooth flow of electrical activity. Neurons send messages using chemicals that cause an electrical signal to be produced. When a neuron is not sending a signal, it is "at rest." An action potentially occurs when a neuron sends information down an axon, away from the cell body.
A seizure occurs when these neurons generate electrical discharges that spread throughout the brain. This can occur with both normal and abnormal nerve cells.
Recurrent seizures or prolonged seizures can cause temporary or permanent damage to the brain and/or muscles. Seizures that last longer than 20-30 minutes can damage the brain's neurons.
Certain areas of the brain are more likely than others to be the source of a seizure. These include the motor cortex, which is responsible for the initiation of body movement, and the temporal lobes, which include the hippocampus (involved in memory) and are found deeper in the brain. The reason these structures are more susceptible to seizures may be that nerve cells in these areas are particularly sensitive to situations that can provoke abnormal electrical transmission, such as decreased oxygen levels, metabolic changes, stress, and infection. A seizure threshold is each individual's balance (probably genetically determined) between excitatory and inhibitory forces in the brain. The relative proportions of each determine whether a person has a low threshold for seizures (because of the higher excitatory balance) or a high threshold (because of greater inhibition). According to this view, a low seizure threshold makes it easier for epilepsy to develop and easier for someone to experience a single seizure.
A seizure is often divided into different stages. The aura is a period or warning prior to a seizure. Individuals may experience unusual smells, visual symptoms, or changes in bodily sensations. The seizure itself is known as the ictus. The period of time after the seizure is called the postictal state.
Seizure disorders are a common neurological problem. In the United States, it has been estimated that more than four million individuals have some form of epilepsy.
Epilepsy can affect individuals at any age.
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types of seizures
A well-recognized classification system for seizures is the International Classification of Epileptic Seizures. This divides seizure types by the location in the brain from which they originate. The two main categories of seizures include partial seizures and generalized seizures.
Partial, or focal, seizures are those that begin in a focal or discreet area of the brain. Partial seizures can be further subdivided into simple partial and complex partial.
Simple partial seizures: In simple partial seizures, no change in consciousness occurs and seizure activity is localized in a specific portion of the brain. Individuals may experience weakness, numbness, and unusual smells or tastes. Twitching of the muscles or limbs, turning the head to the side, paralysis, visual changes, or vertigo (dizziness) may occur. If motor symptoms spread slowly from one part of the body to another, then the seizure is termed Jacksonian epilepsy.
Complex partial seizures (temporal lobe): During complex partial seizures, consciousness is altered or lost during the event. Individuals may have some symptoms similar to those in simple partial seizures but have some change in their ability to interact with the environment. Individuals may exhibit automatisms (automatic repetitive behavior) such as walking in a circle, sitting and standing, or smacking the lips together. Often accompanying these symptoms are the presence of unusual thoughts, such as the feeling of déjà vu (having been someplace before), uncontrollable laughing, fear, visual hallucinations, and experiencing unusual unpleasant odors. These symptoms are generally thought of as being caused by abnormal electrical discharges between neurons in specific areas of the brain, such as the temporal lobe.
Generalized seizures involve larger areas of the brain, often both hemispheres (sides), from the onset. They are further divided into many subtypes. The more common types include tonic-clonic (grand mal), absence (petit mal), and myoclonic seizures.
Tonic-clonic (grand mal): Tonic-clonic seizures, also called grand mal, are the subtype that most people associate with seizures. Specific movements of the arms and legs and/or the face may occur with loss of consciousness. A yell or cry often precedes the loss of consciousness. Individuals may have an aura, or an unusual feeling that often warns the patient that they are about to have a seizure, right before the loss of consciousness. The individual will abruptly collapse and begin to have jerking movements of their body and head. Drooling, biting of the tongue, and urinary incontinence may occur. When the jerking movements stop, the individual may remain unconscious for a period of time. Tonic-clonic seizures usually last 5-20 minutes. Individuals often awaken confused and may sleep for a period of time. Todd's paralysis is a term for when the individual experiences prolonged weakness after the seizure.
Absence (petit mal): Absence or petit mal seizures are when loss of consciousness only occurs and there are no other associated motor symptoms, such as jerking. Usually there is no aura or warning. The loss of consciousness is brief. The individual may appear to be involved with the environment and briefly stop what they are doing, stare for 5-10 seconds, and then continue their activity. No memory of the event exists. Subtle motor movements may accompany the alteration in consciousness.
Myoclonic: Myoclonic seizures are characterized by a brief jerking movement that arises from the central nervous system, usually involving both sides of the body. The movement may be very subtle or very dramatic. There are many different syndromes associated with myoclonic seizures, including juvenile myoclonic epilepsy, West syndrome, and Lennox-Gastaut syndrome. Most cases of myoclonic epilepsy occur during the first five years of life. There is no loss of consciousness with myoclonic seizures.
Other seizure disorders
West Syndrome: West syndrome, also known as infantile spasm, involves a group of symptoms including spasms in infants, retardation of psychomotor development, and a particular abnormality on the electroencephalogram (EEG) known as hypsarrhythmia. Hypsarrhythmia is the abnormally high amplitude waves and a background of irregular spikes seen in EEG. Infantile spasms are characterized by a particular posturing of the infant's body, in which the child assumes a jack-knife, or folded position. These spasms may occur frequently in the course of the day or may be continuous. Neurological problems are ultimately found in most of these children. The hypsarrhythmia pattern seen on the EEG is a grossly disorganized pattern of electrical brain activity. It is often difficult to control the seizures in this syndrome because they usually respond poorly to most anticonvulsant medications.
Lennox-Gastaut Syndrome: Lennox-Gastaut syndrome, also known as childhood epileptic encephalopathy, is a devastating pediatric (usually before the age of four) epilepsy syndrome constituting 1-4% of childhood epilepsies. The syndrome is characterized by multiple types of seizures, mental retardation or regression, and abnormal EEG. The seizures include the myoclonic seizures, absence seizures, and atonic seizures. Absence seizures may involve staring and brief episodes of unconsciousness. They may occur in cycles and are associated with EEG findings different from those seen in typical absence seizures. Atonic seizures may be associated with sudden loss of muscle tone.
Status Epilepticus: Status epilepticus is prolonged, repetitive seizure activity that lasts more than 20-30 minutes, during which time the patient is unconscious. Status epilepticus is a medical emergency with a significantly poor outcome. It can result in death if not treated aggressively. Its causes include improper use of certain medications, stroke, infection, trauma, cardiac arrest, illicit drug overdose (such as cocaine or methamphetamine), and brain tumor.
It is recommended by healthcare professionals for individuals with epilepsy and seizure disorders to discuss their condition with family members, friends, and co-workers in case seizures occur. Individuals should instruct the others to stay calm; do not try to keep the individual from moving; take away items that could cause injury if the person falls or bumps into them; do not move the individual to another place; and to gently turn the individual onto his or her side so any fluid in the mouth can safely come out. Do not try to force the individual's mouth open or put anything in it; understand that seizures are usually not life-threatening. A doctor or an ambulance should be called if the individual has seizures that lasts longer than 10-15 minutes; and when the seizure is over, watch the individual for signs of confusion.
Health care providers recommend calling a doctor in the following situations: anytime seizures change, either in number or in the way the individual feels during them; anytime the individual feels ill or sick; or anytime there are changes in seizure medications or if the individual take any other medications. It is very important to take prescribed medications as directed. It is also very important for an individual to tell their doctor about herbs and other dietary supplements they may be taking. It is best to avoid taking dietary supplements without a doctor's approval.
Although the laws vary somewhat from state to state, most states have rules regarding when seizure patients can legally resume driving. Typically, individuals must have been seizure-free six months to a year. While doctors generally are not required to report patient seizures to their state motor vehicle departments, individuals are expected to comply with the laws in their state.