Epileptic seizures (colloquially a fit) are brief episodes of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can vary from uncontrolled jerking movement (tonic-clonic seizure) to as subtle as a momentary loss of awareness (absence seizure). The syndrome of recurrent, unprovoked seizures is termed epilepsy, but seizures can also occur in people who do not have epilepsy. Additionally, there are a number of conditions that look like seizures but are not.
After a first seizure, treatment is generally not needed unless specific problems are found on either electroencephalogram or imaging of the brain.
About 5–10% of all people will have an unprovoked seizure by the age of 80 and the chance of experiencing a second seizure is between 40% and 50%. Epilepsy affects about 1% of the population currently and affects about 4% of the population at some point in time. Most of those affected- nearly 80%- live in developing countries.
The signs and symptoms of seizures vary depending on the type. The most common type of seizures are convulsive (60%). Two-thirds of these begin as focal seizures and become generalized while one third begin as generalized seizures. The remaining 40% of seizures are non-convulsive, an example of which is absence seizures
Focal seizures are often preceded by certain experiences, known as an aura. These may include: sensory, visual, psychic, autonomic, olfactory or motor phenomena.
In a complex partial seizure a person may appear confused or dazed and will not be able to respond to questions or direction. Focal seizure may become generalized.
Jerking activity may start in a specific muscle group and spread to surrounding muscle groups in which case it is known as a Jacksonian march. Unusual activities that are not consciously created may occur. These are known as automatisms and include simple activities like smacking of the lips or more complex activities such as attempts to pick something up.
There are six main types of generalized seizures: tonic-clonic, tonic, clonic, myoclonic, absence, and atonic seizures. They all involve a loss of consciousness and typically happen without warning.
Tonic-clonic seizures present with a contraction of the limbs followed by their extension along with arching of the back which lasts 10–30 seconds. A cry may be heard due to contraction of the chest muscles. The limbs then begin to shake in unison. After the shaking has stopped it may take 10–30 minutes for the person to return to normal.
Tonic seizures produce constant contractions of the muscles. The person may turn blue if breathing is impaired.
Clonic seizures involve shaking of the limbs in unison.
Myoclonic seizures involve spasms of muscles in either a few areas or generalized through the body.
Absence seizures can be subtle, with only a slight turn of the head or eye blinking. The person often does not fall over and may return to normal right after the seizure ends, though there may also be a period of post-ictal disorientation.
Atonic seizures involve the loss of muscle activity for greater than one second. This typically occurs bilaterally (on both sides of the body).
A seizure can last from a few seconds to more than five minutes at which point it is known as status epilepticus. Most tonic-clonic seizures last less than two or three minutes. Absence seizures are usually around 10 seconds in duration.
After the active portion of a seizure, there is typically a period of confusion referred to as the postictal period before a normal level of consciousness returns. This usually lasts 3 to 15 minutes but may last for hours. Other common symptoms include: feeling tired, headache, difficulty speaking, and abnormal behavior.Psychosis after a seizure is relatively common, occurring in between 6 and 10% of people. Often people do not remember what occurred during this time.
Seizures have a number of causes. Of those with seizure about 25% have epilepsy. A number of conditions are associated with seizures but are not epilepsy including: most febrile seizures and those that occur around an acute infection, stroke, or toxicity. These seizures are known as "acute symptomatic" or "provoked" seizures and are part of the seizure-related disorders. In many the cause is unknown.
Different causes of seizures are common in certain age groups.
seizures in a person with a shunt may indicated failure
haemorrhagic stroke can occasionally present with seizures, embolic strokes generally do not (though epilepsy is a common later complication); cerebral venous sinus thrombosis, a rare type of stroke, is more likely to be accompanied by seizures than other types of stroke
Normally brain electrical activity is non synchronous. In epileptic seizures, due to problems within the brain, a group of neurons begin firing in an abnormal, excessive, and synchronized manner. This results in a wave of depolarization known as a paroxysmal depolarizing shift.
Normally after an excitatory neuron fires it becomes more resistant to firing for a period of time. This is due in part from the effect of inhibitory neurons, electrical changes within the excitatory neuron, and the negative effects of adenosine. In epilepsy the resistance of excitatory neurons to fire during this period is decreased. This may occur due to changes in ion channels or inhibitory neurons not functioning properly. This then results in a specific area from which seizures may develop, known as a "seizure focus". Another cause of epilepsy may be the up regulation of excitatory circuits or down regulation of inhibitory circuits follow an injury to the brain. These secondary epilepsies, occur through processes known as epileptogenesis. Failure of the blood–brain barrier may also be a causal mechanism.
Focal seizures begin in one hemisphere of the brain while generalized seizures begin in both hemispheres. Some types of seizures may change brain structure, while others appear to have little effect.Gliosis, neuronal loss, and atrophy of specific areas of the brain are linked to epilepsy but it is unclear if epilepsy causes these changes or if these changes result in epilepsy.
An EEG can aid in locating the focus of the epileptic seizure.
Focal seizures were previously divided into simple partial or complex partial seizure. This is no longer recommended with the preference to describe what has occurred during a seizure.
Most people are in a postictal state following a seizure (drowsy or confused). There may be signs of other injuries. A small study found that a bite to the side of the tongue was very helpful when present: while only a quarter of those with seizures had such a bite, most with such a bite had seizures.
In adults testing electrolytes, blood glucose and calcium levels is important to rules these out as causes. As is an electrocardiogram. A lumbar puncture may be useful to diagnose a central nervous system infection but is not routinely needed. Routine antiseizure medical levels in the blood are not required in adults or children. In children additional tests may be required.
A high blood prolactin level within the first 20 minutes following a seizure may be useful to confirm an epileptic seizure as opposed to psychogenic non-epileptic seizure. Serum prolactin level is less useful for detecting partial seizures. If it is normal an epileptic seizure is still possible and a serum prolactin does not separate epileptic seizures from syncope. It is not recommended as a routine part of diagnosis epilepsy.
An electroencephalography is only recommended in those who likely had an epileptic seizure and may help determine the type of seizure or syndrome present. In children it is typically only needed after a second seizure. It cannot be used to rule out the diagnosis and may be falsely positive in those without the disease. It certain situations it may be useful to prefer the EEG while sleeping or sleep deprived.
Diagnostic imaging by CT scan and MRI is recommended after a first non-febrile seizure to detect structural problems inside the brain. MRI is generally a better imaging test except when intracranial bleeding is suspected. Imaging may be done at a later point in time in those who return to their normal selves while in the emergency room. If a person has a previous diagnosis of epilepsy with previous imaging repeat imaging is not usually needed with subsequent seizures.
Potentially sharp or dangerous objects should also be moved from the vicinity, so that the individual is not hurt. After the seizure if the person is not fully conscious and alert, they should be placed in the recovery position. A seizure longer than five minutes is a medical emergency known as status epilepticus. Contrary to a common misconception, bystanders should not attempt to force objects into the mouth of the person suffering a seizure, as doing so may cause injury to the teeth and gums.
The first line treatment of choice for someone who is actively seizing is a benzodiazepine, most guidelines recommend lorazepam. This may be repeated if there is no effect after 10 minutes. If there is no effect after two doses, barbiturates or propofol may be used.
Ongoing medication is not typically needed after a first seizure and is generally only recommended after a second one has occurred or in those with structural lesions in the brain. After a second seizure anti-epileptic medications are recommended. Approximately 70% of the people are able to get full control with continuous use of medication. Typically one type of anticonvulsant is preferred.
In seizures related to toxins, up to two doses of benzodiazepines should be used. If this is not effective pyridoxine is recommended. Phenytoin should generally not be used.
Helmets may be used to provide protection of the head during a seizure. Some claim that seizure response dogs, a form of service dog, can predict seizures. Evidence for this, however, is poor.
Following a first seizure the risk of more seizures in the next two years is 40–50%. The greatest predictors of more seizures is problems on either the electroencephalogram or on imaging of the brain. In adults, after 6 months seizure free, after a first seizure the risk of a subsequent seizure in the next year is less than 20% regardless of treatment. Up to 7% of seizure that present to the emergency are in status epilepticus. In those with a status epilepticus mortality is between 10 and 40%. Those who have a seizure that is provoked (occurring right around an acute brain event or toxic exposure) have a low risk of re-occurrence; however, have a higher risk of death compared to those with epilepsy.
Around 5–10% of people who live to 80 years old have at least one epileptic seizure. About 0.7% of people in the United States have a seizure in a given year.
Rates are highest in those less than a year of age and greater than 55. About 1% or 50 million people currently have epilepsy worldwide. About 4% of people develop epilepsy at some point in time.
The word epilepsy is derived from the Greek word for "attack." Seizures were long viewed as an otherworldly condition being referred to by Hippocrates in 400B.C. as "the sacred disease".
In the mid 1800s the first anti seizure medication, bromide, was introduced.
Following standardization proposals devised by Henri Gastaut and published in 1970, terms such as "petit mal", "grand mal", "Jacksonian", "psychomotor", and "temporal-lobe seizure" have fallen into disuse.
Society and culture
Seizures result in direct economic costs of about one billion dollars in the United States. Epilepsy results in economic costs in Europe of around 15.5 billion Euros in 2004. In India epilepsy is estimated to result in costs of 1.7 billion USD or 0.5% of the GDP. They make up about 1% of emergency department visits (2% for emergency departments for children) in the United States.
Many areas of the world require there to be a minimum of six months from the last seizure before people can return to driving.
Scientific work into the prediction of epileptic seizures began in the 1970s. Several techniques and methods have been proposed, but evidence regarding their usefulness is still lacking.
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