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In seizure disorders, the brain's electrical activity is periodically disturbed, resulting in some degree of temporary brain dysfunction.
Many people have unusual sensations just before a seizure starts.
Some seizures cause uncontrollable shaking and loss of consciousness, but more often, people simply stop moving or become unaware of what is happening.
Doctors suspect the diagnosis based on symptoms, but imaging of the brain, blood tests, and electroencephalography (to record the brain’s electrical activity) are usually needed to identify the cause.
If needed, drugs can usually help prevent seizures.
Normal brain function requires an orderly, organized, coordinated discharge of electrical impulses. Electrical impulses enable the brain to communicate with the spinal cord, nerves, and muscles as well as within itself. Seizures may result when the brain’s electrical activity is disrupted.
There are two basic types of seizures:
Epileptic: These seizures have no apparent cause (or trigger) and occur repeatedly. These seizures are called a seizure disorder or epilepsy.
Nonepileptic: These seizures are triggered (provoked) by a disorder or another condition that irritates the brain. In children, a fever can trigger a nonepileptic seizure (called a febrile seizure—see Febrile Seizures).
Certain mental disorders can cause symptoms that resemble seizures, called psychogenic nonepileptic seizures.
About 2% of adults have a seizure at some time during their life. Two thirds of these people never have another one. Seizure disorders commonly begin in early childhood or in late adulthood.
Which causes are most common depend on when seizures start:
Before age 2: High fevers or temporary metabolic abnormalities, such as abnormal blood levels of sugar (glucose), calcium, magnesium, vitamin B6, or sodium, can trigger one or more seizures. Seizures do not occur once the fever or abnormality resolves. If the seizures recur without such triggers, the cause is likely to be an injury during birth, a birth defect, or a hereditary metabolic abnormality or brain disorder.
2 to 14 years: Often, the cause is unknown.
Adults: A head injury, stroke, or tumor may damage the brain, causing a seizure. Alcohol withdrawal (caused by suddenly stopping drinking) is a common cause of seizures. However, in about half of people in this age group, the cause is unknown.
Seizures with no identifiable cause are called idiopathic.
Conditions that irritate the brain—such as injuries, certain drugs, sleep deprivation, infections, fever—or that deprive the brain of oxygen or fuel—such as abnormal heart rhythms, a low level of oxygen in the blood, or a very low level of sugar in the blood—can trigger a single seizure whether a person has a seizure disorder or not. A single seizure that results from such a stimulus is called a provoked seizure (and thus is a nonepileptic seizure). People with a seizure disorder are more likely to have a seizure when they are under excess physical or emotional stress, when they are intoxicated or deprived of sleep, or when they have suddenly stopped drinking or using sedatives. Avoiding these conditions can help prevent seizures.
Rarely, seizures are triggered by repetitive sounds, flashing lights, video games, or even touching certain parts of the body. In such cases, the disorder is called reflex epilepsy.
Causes of Seizures
In about 20% of people who have a seizure disorder, seizures are preceded by unusual sensations (called aura), such as the following:
Almost all seizures are relatively brief, lasting from a few seconds to a few minutes. Most seizures last 1 to 2 minutes. When a seizure stops, people may have a headache, sore muscles, unusual sensations, confusion, and profound fatigue. These after-effects are called the postictal state. In some people, one side of the body is weak, and the weakness lasts longer than the seizure (a disorder called Todd paralysis). Most people who have a seizure disorder look and behave normally between seizures. Some people bite their tongue and lose control of the bladder and/or bowels during a seizure.
An intensely pleasant or unpleasant taste if the part of the cerebrum called the insula is affected
Visual hallucinations (seeing unformed images) if the occipital lobe is affected
Inability to speak if the area that controls speech (located in the frontal lobe) is affected
A convulsion (jerking and spasms of muscles throughout the body) if large areas on both sides of the brain are affected
Other possible symptoms include numbness or tingling in a specific body part, brief episodes of unresponsiveness, loss of consciousness, confusion, and loss of muscle or bladder control. People may vomit if they lose consciousness.
Symptoms also vary depending on whether the seizure is partial or generalized. About 70% of people have only one type of seizure. The rest have two or more types.
Only one side of the brain is affected. Partial seizures may be simple or complex.
In simple partial seizures, abnormal electrical discharges begin in a small area of the brain and remain confined to that area. Because only a small area of the brain is affected, symptoms are related to the function controlled by that area. For example, if the small area of the brain that controls the right arm’s movements (in the left frontal lobe) is affected, the right arm may involuntarily be lifted up and the head may turn toward the lifted arm. People are completely conscious and aware of the surroundings. A simple partial seizure may progress to a complex partial seizure.
Jacksonian seizures are a type of simple partial seizures. Symptoms start in one part of the body, then spread to another. Abnormal movements may occur in the hand or foot, then move up the limb as the electrical activity spreads in the brain. People are completely aware of what is occurring during the seizure.
In complex partial seizures, abnormal electrical discharges begin in a small area of the temporal lobe or frontal lobe and quickly spread to other nearby areas. The seizures usually begin with an aura that lasts 1 to 2 minutes. During the aura, people start to lose touch with the surroundings. During the seizure, consciousness is impaired but not completely lost. People may do the following:
Some people can converse, but their conversation lacks spontaneity, and the content is somewhat sparse. They may be confused and disoriented. This state may last for several minutes. Most people do not remember what happened during the seizure (a condition called postictal amnesia). Some people then recover fully. In others, the abnormal electrical discharge spreads to adjacent areas and to the other side of the brain, resulting in a generalized seizure. Generalized seizures that result from partial seizures are called secondarily generalized seizures.
Epilepsia partialis continua is rare. Seizures occur every few seconds or minutes for days to years at a time. They typically affect an arm, a hand, or one side of the face. These seizures usually result from localized brain damage (such as scarring due to a stroke) in adults or from inflammation of the brain (as occurs in encephalitis and measles) in children.
Large areas on both sides of the brain are affected. Generalized seizures often cause loss of consciousness and abnormal movements, usually immediately. Loss of consciousness may be brief or last a long time.
Generalized seizures include the following:
In generalized tonic-clonic seizures , muscles contract (the tonic part), then rapidly alternate between contracting and relaxing (the clonic part). These seizures may be primary or secondary.
Primary generalized seizures begin with abnormal discharges in a deep, central part of the brain and spread simultaneously to both sides of the brain. Secondary generalized tonic-clonic (grand mal) seizures usually begin with an abnormal electrical discharge in a small area of one side of the brain, resulting in a simple or complex partial seizure. The discharge then quickly spreads to both sides of the brain, causing the entire brain to malfunction. In both types, consciousness is temporarily lost and a convulsion occurs when the abnormal discharges spread to both sides of the brain.
In primary generalized seizures, there is no aura. During the seizure, people may do the following:
The seizures usually last 1 to 2 minutes. Afterward, some people have a headache, are temporarily confused, and feel extremely tired. These symptoms may last from minutes to hours. Most people do not remember what happened during the seizure.
Absence seizures may be typical (petit mal) or atypical.
Typical absence seizures usually begin in childhood, usually between the ages of 5 and 15 and do not continue into adulthood. However, adults occasionally have typical absence seizures. Unlike tonic-clonic seizures, absence seizures do not cause convulsions or other dramatic symptoms. People do not fall down, collapse, or move jerkily. Instead, they have episodes of staring with fluttering eyelids and sometimes twitching facial muscles. They are completely unaware of their surroundings. These episodes last 10 to 30 seconds. People abruptly stop what they are doing and resume it just as abruptly. They experience no after-effects and do not know that a seizure has occurred. Without treatment, many people have several seizures a day. Seizures often occur when people are sitting quietly. Seizures rarely occur during exercise. Hyperventilation can trigger a seizure.
Atypical absence seizures are less common. They last longer than typical absence seizures, jerking and other movements are more pronounced, and people are more aware of their surroundings. Most people with atypical absence seizures have neurologic abnormalities or developmental delays. Seizures usually continue into adulthood.
Atonic seizures occur primarily in children. They are characterized by a brief but complete loss of muscle tone and consciousness. They cause children to fall to the ground, sometimes resulting in injury.
Tonic seizures occur commonly during sleep. Muscle tone increases abruptly or gradually, causing muscles to stiffen. The seizures typically last only 10 to 15 seconds but can cause people, if standing, to fall to the ground. Most people do not lose consciousness. If seizures last longer, muscles may jerk a few times as the seizure ends.
Atypical absence seizures, atonic seizures, and tonic seizures usually occur as part of a severe form of epilepsy called Lennox-Gastaut syndrome, which begins before children are 4 years old.
Myoclonic seizures are characterized by quick jerks of one or several limbs or the trunk. The seizures are brief and do not cause loss of consciousness, but they may occur repetitively and progress to a tonic-clonic seizure with loss of consciousness.
Juvenile myoclonic epilepsy typically begins during adolescence. Typically, seizures begin with quick jerks of both arms. About 90% of these seizures are followed by tonic-clonic seizures. Some people also have absence seizures. The seizures often occur when people awaken in the morning, especially if they are sleep-deprived. Drinking alcohol also makes these seizures more likely.
This disorder is the most serious seizure disorder and is considered a medical emergency because the seizure does not stop. Electrical discharges occur throughout the brain, causing a generalized tonic-clonic seizure.
Status epilepticus is diagnosed when a seizure lasts more than 5 minutes or when people do not completely regain consciousness between two or more seizures. People have convulsions with intense muscle contractions and often cannot breathe adequately. Body temperature increases. Without rapid treatment, the heart and brain can become overtaxed and permanently damaged, sometimes resulting in death.
Seizures may have serious consequences. Intense, rapid muscle contractions can cause injuries, including broken bones. Sudden loss of consciousness can cause serious injury due to falls and accidents. People may have numerous seizures without incurring serious brain damage. However, seizures that recur and cause convulsions may eventually impair intelligence.
If seizures are not well controlled, people may be unable to get a driver’s license. They may have difficulty keeping a job or getting insurance. They may be socially stigmatized. As a result, their quality of life may be substantially reduced.
If seizures are not completely controlled, people are twice as likely to die as those who do not have seizures. A few people die suddenly for no apparent reason—a complication called sudden unexplained death in epilepsy.
Doctors diagnose a seizure disorder when people have at least two unprovoked seizures that occur at different times. The diagnosis is based on symptoms and the observations of eyewitnesses. Symptoms that suggest a seizure include loss of consciousness, muscle spasms that shake the body, loss of bladder control, sudden confusion, and inability to pay attention. However, seizures cause such symptoms much less often than most people think. A brief loss of consciousness is more likely to be fainting (syncope—see Fainting) than a seizure.
An eyewitness report of the episode can be very helpful to doctors. An eyewitness can describe exactly what happened, whereas people who have an episode usually cannot. Doctors need to have an accurate description, including the following:
Although eyewitnesses may be too frightened during the seizure to remember all details, whatever they can remember can help. If possible, how long a seizure lasts should be timed with a watch or other device. Seizures that last only 1 or 2 minutes can seem to go on forever.
Doctors also need to know what people experienced before the episode: whether they had a premonition or warning that something unusual was about to happen and whether anything, such as certain sounds or flashing lights, seemed to trigger the episode. Doctors ask whether people have had a disorder that can cause seizures (such as a brain infection) or a head injury. Doctors also ask about which drugs (including alcohol) people are taking or have recently stopped. A thorough physical examination is done. It may provide clues to the cause of the symptoms.
People are usually evaluated in an emergency department. If a seizure disorder has already been diagnosed and people have completely recovered, they may be evaluated in a doctor’s office.
Once a seizure is diagnosed, more tests are usually needed to identify the cause. People known to have a seizure disorder may not need additional tests. In others, blood tests are often done to measure the levels of substances such as sugar, calcium, sodium, and magnesium and to determine whether the liver and kidneys are functioning normally. A sample of urine may be analyzed to check for recreational drugs that may not be reported. Such drugs can trigger a seizure. Electrocardiography (see Electrocardiography) may be done to check for an abnormal heart rhythm. Because an abnormal heart rhythm can greatly reduce blood flow (and therefore oxygen supply) to the brain, it can trigger loss of consciousness and occasionally a seizure or symptoms that resemble a seizure.
Magnetic resonance imaging (MRI) is usually done. It provides detailed images of brain abnormalities that could be causing seizures. If doctors suspect a brain disorder that needs to be treated right away (such as bleeding or a stroke) and MRI cannot be done immediately, computed tomography (CT), which is typically readily available, is usually done.
If doctors suspect a brain infection such as meningitis or encephalitis, a spinal tap (lumbar puncture—see Figure: How a Spinal Tap Is Done) is usually done.
Electroencephalography (EEG) can help confirm the diagnosis. EEG is a painless, safe procedure that records electrical activity in the brain (see Tests for Brain, Spinal Cord, and Nerve Disorders : Electroencephalography). Doctors examine the recording (electroencephalogram) for evidence of abnormal electrical discharges. Because the recording time is limited, EEG can miss abnormalities, and results may be normal, even in people who have a seizure disorder. EEG is sometimes scheduled after people have been deprived of sleep for 18 to 24 hours because lack of sleep makes abnormal discharges more likely to occur.
Brain Activity During a Seizure
EEG may be repeated because when done a second or even a third time, it may detect the cause, which was missed the first time the test was done.
If the diagnosis is still uncertain, specialized tests, such as video-EEG monitoring, can be done at an epilepsy center. For this test, people are admitted to a hospital for 2 to 7 days, and EEG is done while they are video-taped. If people are taking an anticonvulsant, it is often stopped to increase the likelihood of a seizure. If a seizure occurs, doctors compare the EEG recording with the video recording of the seizure. They may then be able to identify the type of seizure and the area of the brain where the seizure began.
If the cause can be identified and eliminated, no additional treatment is necessary. For example, if a low blood sugar (glucose) level (hypoglycemia—see Hypoglycemia) caused the seizure, glucose is given, and the disorder causing the low level is treated. Other treatable causes include an infection, certain tumors, and an abnormal sodium level.
If people have a seizure disorder, general measures plus drugs are usually sufficient. If drugs are ineffective, surgery may be recommended.
Exercise is recommended and social activities are encouraged. However, people who have a seizure disorder may have to make some adjustments. For example, they should eliminate or limit their consumption of alcoholic beverages and should not use recreational drugs. They should refrain from activities in which a sudden loss of consciousness could result in serious injury. For example, they should not bathe in a bathtub, climb, swim, or operate power tools. After seizures are controlled (typically for at least 6 months), they can do these activities if adequate precautions are taken. For example, they should swim only when lifeguards are present. In most states, laws prohibit people with a seizure disorder from driving until they have been free of seizures for at least 6 months to 1 year.
A family member or close friend should be trained to help if a seizure occurs. Attempting to put an object (such as a spoon) in the person’s mouth to protect the person’s tongue should not be tried. Such efforts can do more harm than good. The teeth may be damaged, or the person may bite the helper unintentionally as the jaw muscles contract. However, helpers should do the following during a seizure:
If a pillow is unavailable, helpers can put their foot or place an item of clothing under the person’s head.
People who lose consciousness should be rolled onto one side to ease breathing and help prevent them from inhaling vomit. People who have had a seizure should not be left alone until they have awakened completely, are no longer confused, and can move about normally. Usually, their doctor should be notified.
These drugs reduce the risk of having another seizure. Usually, they are prescribed only if people have had more than one seizure and if reversible causes, such as low blood sugar, have been identified and completely eliminated. They are usually not prescribed when people have had only one generalized seizure. Most anticonvulsants are taken by mouth.
Anticonvulsants can completely stop seizures in about one third of people who have them and greatly reduce the frequency of seizures in another third. Almost two thirds of people who respond to anticonvulsants can eventually stop taking them without having a relapse. However, anticonvulsants are ineffective in about 10 to 20% of people with a seizure disorder. These people are referred to a seizure center and evaluated for surgery.
There are many different types of anticonvulsants. Which one is effective depends on the type of seizure and other factors. For most people, taking one anticonvulsant, usually the first or second one tried, controls seizures. If seizures recur, different anticonvulsants are tried. In such cases, determining which anticonvulsant is effective may take several months. Some people have to take several drugs, which increases the risk of side effects. Some anticonvulsants are not used alone but only with other anticonvulsants.
Doctors take care to determine the appropriate dose of an anticonvulsant for each person. The best dose is the smallest dose that stops all seizures while having the fewest side effects. Doctors ask people about side effects, then adjust the dose if needed. Sometimes doctors also measure the level of anticonvulsant in the blood. Anticonvulsants should be taken just as prescribed. People who take anticonvulsants to control seizures should see a doctor regularly for dose adjustment and should always wear a Medic Alert bracelet inscribed with the type of seizure disorder and the drug being taken.
Anticonvulsants can interfere with the effectiveness of other drugs, and vice versa. Consequently, people should make sure their doctor knows all the drugs they are taking before they start taking anticonvulsants. They should also talk to their doctor and possibly their pharmacist before they start taking any other drugs, including over-the-counter drugs.
After seizures are controlled, people take the anticonvulsant until they have been seizure-free for at least 2 years. Then, the dose of the drug may be decreased gradually, and the drug eventually stopped. If a seizure recurs after the anticonvulsant is stopped, people may have to take an anticonvulsant indefinitely. Seizures usually recur within 2 years if they are going to. A recurrence is more likely in people who have had any of the following:
Anticonvulsants, although very effective, may have side effects. Many cause drowsiness, but some may make children hyperactive. Blood tests are done periodically to determine whether an anticonvulsant is impairing kidney or liver function or reducing the number of blood cells. People taking anticonvulsants should be aware of possible side effects and should consult their doctor at the first sign of side effects.
For women who have a seizure disorder and are pregnant, taking an anticonvulsant increases the risk of miscarrying or of having a baby with a birth defect (see Table: Categories of Risk for Drugs During Pregnancy). However, stopping the anticonvulsant may be more harmful to the woman and the baby. Having a generalized seizure during pregnancy can injure or kill the fetus. All women who are of childbearing age and taking an anticonvulsant should take folate supplements to reduce the risk of having a baby with a birth defect.
Drugs Used to Treat Seizures
Emergency treatment is required for status epilepticus and seizures that last more than 5 minutes. Large doses of one or more anticonvulsants (often starting with a benzodiazepine, such as lorazepam) are given intravenously as quickly as possible to stop the seizure. The sooner anticonvulsants are started, the better and the more easily seizures are controlled.
Measures to prevent injuries are taken during the prolonged seizure. People are monitored closely to make sure breathing is adequate. If it is not, a tube is inserted to help with breathing—a procedure called intubation. If seizures persist, a general anesthetic is given to stop them.
If people continue to have seizures while taking two or more anticonvulsants or if they cannot tolerate side effects of the anticonvulsants, brain surgery may be done. These people are tested at specialized epilepsy centers to determine whether surgery can help. Tests may include the following:
Functional MRI: To determine which areas in the brain are causing seizures
Single-photon emission CT (SPECT): To check for areas with decreased blood flow around the time of a seizure, which may indicate which areas in the brain are causing seizures
EEG combined with magnets used for imaging (magnetic source imaging): Also to help determine which areas in the brain are causing seizures
If a defect in the brain (such as a scar) can be identified as the cause and is confined to a small area, surgically removing that area can eliminate seizures in up to 60% of people, or it may reduce the severity and frequency of seizures. Surgically cutting the nerve fibers that connect the two sides of the brain (corpus callosum) may help people who have seizures that originate in several areas of the brain or that spread to all parts of the brain very quickly. This procedure usually has no appreciable side effects. However, even if surgery reduces the frequency and severity of seizures, many people need to continue to take anticonvulsants. However, they can usually take lower doses or fewer drugs.
Before and after surgery, a psychologic and neurologic evaluation (see Physical Examination) may be done to determine how well the brain is functioning.
Electrical stimulation of the 10th cranial nerve (vagus nerve) can reduce the number of partial seizures by more than one half in some people. This treatment is used when seizures continue despite use of anticonvulsants and when surgery is not a possibility. It reduces the number of seizures in about 40% of people.
The vagus nerve is thought to have indirect connections to areas of the brain often involved in causing seizures. A device that looks like a heart pacemaker (vagus nerve stimulator) is implanted under the left collarbone and is connected to the vagus nerve in the neck with a wire that runs under the skin. The device causes a small bulge under the skin. The operation is done on an outpatient basis and takes about 1 to 2 hours.
The device is programmed to periodically stimulate the vagus nerve. Also, people are given a magnet, which they can use to stimulate the vagus nerve when they sense that a seizure is about to begin Vagus nerve stimulation is used in addition to anticonvulsants. Side effects include hoarseness, cough, and deepening of the voice when the nerve is stimulated.
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