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Period of symptoms due to excessive or synchronous neuronal brain activity From Wikipedia, the free encyclopedia
A seizure is a sudden change in behavior, movement, and/or consciousness due to abnormal electrical activity in the brain.[3][6] Seizures can look different in different people. It can be uncontrolled shaking of the whole body (tonic-clonic seizures) or a person spacing out for a few seconds (absence seizures).[3][12][8] Most seizures last less than two minutes.[5] They are then followed by confusion/drowsiness before the person returns to normal.[3][8] If a seizure lasts longer than 5 minutes, it is a medical emergency (status epilepticus) and needs immediate treatment.[3][5][13]
| Epileptic seizure | |
|---|---|
| Other names | Epileptic fit,[1] seizure, fit, convulsions[2] |
| |
| Generalized 3 Hz spike and wave discharges in an electroencephalogram (EEG) of a patient with epilepsy | |
| Specialty | Neurology, emergency medicine |
| Symptoms | Variable[3] |
| Complications | Falling, drowning, car accidents, pregnancy complications, emotional health issues[4] |
| Duration | Typically < 2 minutes[5] |
| Types | Focal, generalized; Provoked, unprovoked[6] |
| Causes | Provoked: Low blood sugar, alcohol withdrawal, low blood sodium, fever, brain infection, traumatic brain injury[3][6] Unprovoked: Unknown, brain injury, brain tumor, previous stroke[6][7][3] |
| Diagnostic method | Based on symptoms, blood tests, medical imaging, electroencephalography[7] |
| Differential diagnosis | Syncope, psychogenic non-epileptic seizure, migraine aura, transient ischemic attack[3][8] |
| Treatment | Less than 5 min: Place person on their side, remove nearby dangerous objects More than 5 min: Treat as per status epilepticus[3][5][9] |
| Frequency | ~10% of people (overall worldwide lifetime risk)[10][11] |
Seizures can be classified as provoked or unprovoked.[3][6] Provoked seizures have a cause that can be fixed, such as low blood sugar, alcohol withdrawal, high fever, recent stroke, and recent head trauma.[3][6] Unprovoked seizures have no clear cause or fixable cause.[3][6][7] Examples include past strokes, brain tumors, brain vessel malformations, and genetic disorders.[3] Sometimes, no cause is found, and this is called idiopathic.[5][14] After a first unprovoked seizure, the chance of experiencing a second one is about 40% within 2 years.[5][15] People with repeated unprovoked seizures are diagnosed with epilepsy.[5][6]
Doctors assess a seizure by first ruling out other conditions that look similar to seizures, such as fainting and strokes.[3][8] This includes taking a detailed history and ordering blood tests.[3][14] They may also order an electroencephalogram (EEG) and brain imaging (CT and/or MRI).[3][7] If this is a person's first seizure and it's provoked, treatment of the cause is usually enough to treat the seizure.[3] If the seizure is unprovoked, brain imaging is abnormal, and/or EEG is abnormal, it is recommended to start anti-seizure medications.[3][7][15]
A seizure can last from a few seconds to 5 minutes.[5] Once it reaches and passes 5 minutes, it is known as status epilepticus.[3][5][13] Accidental urination (urinary incontinence), stool leaking (fecal incontinence), tongue biting, foaming of the mouth, and turning blue due to inability to breathe commonly are seen in seizures.[3][8]
A period of confusion typically follows the seizure that lasts from seconds to hours before a person returns to normal. This period is called a postictal period.[16] Other symptoms during this period include drowsiness, headache, difficulty speaking, psychosis, and weakness.[16][17][18]
Observable signs and symptoms of seizures vary depending on the type.[3][14] Seizures can be classified into generalized seizures and focal seizures, depending on what part of the brain is involved.[3][14]
Focal seizures affect a specific area of the brain, not both sides.[14] It may turn into a generalized seizure if the seizure spreads through the brain.[3][14][8] Consciousness may or may not be impaired.[3][5] The signs and symptoms of these seizures depends on the location of the brain that is affected. Focal seizures usually consist of motor symptoms or sensory symptoms.[3]
Generalized seizures affect both sides of the brain and typically involve both sides of the body.[3] They all involve a loss of consciousness and usually happen without warning.[3][14] There are six main types of generalized seizures: tonic-clonic, tonic, clonic, myoclonic, absence, and atonic seizures.[3]
Seizures have a number of causes. Seizures can be classified into provoked or unprovoked.[3] Provoked seizures have a cause that is temporary and reversible.[3] They are also known as Acute Symptomatic Seizures as they occur closely after the injury.[21] Unprovoked seizures do not have a known cause or the cause is not reversible.[3] Unprovoked seizures are typically considered epilepsy and treated as epilepsy.[3][8] Of those who have a seizure, about 25% have epilepsy.[22] Those with epilepsy may have certain triggers that they know cause seizures to occur, including emotional stress, sleep deprivation, and flickering lights.[5]
Dehydration can trigger epileptic seizures by changing electrolyte balances.[23] Low blood sugar, low blood sodium, high blood sugar, high blood sodium, low blood calcium, high blood urea, and low blood magnesium levels may cause seizures.[3][5][23]
Up to 9% of status epilepticus cases occur due to drug intoxication.[24] Common drugs involved include antidepressants, stimulants (cocaine), and antihistamines.[24] Withdrawal seizures commonly occur after prolonged alcohol or sedative use.[3][24] In people who are at risk of developing epileptic seizures, common herbal medicines such as ephedra, ginkgo biloba and wormwood can provoke seizures.[25]
Systemic infection with high fever is a common cause of seizures, especially in children.[3][26] These are called febrile seizures and occur in 2–5% of children between the ages of six months and five years.[27][26] Acute infection of the brain, such as encephalitis or meningitis are also causes of seizures.[3]
Acute stroke or brain bleed may lead to seizures.[3] Stroke is the most common cause of seizures in the elderly population.[28] Post-stroke seizures occur in 5-7% of those with ischemic strokes.[29] Its higher in those who experienced brain bleeds, with 10-16% risk in those patients.[29] Recent traumatic brain injury may also lead to seizures. 1 to 5 of every 10 people who have had traumatic brain injury have experienced at least one seizure.[30] Seizures may occur within 7 days of the injury (early posttraumatic seizure) or after 7 days has passed (late posttraumatic seizure).[30]
Space-occupying lesions in the brain (abscesses, tumours) are one cause of unprovoked seizures.[3] In people with brain tumours, the frequency of epilepsy depends on the location of the tumor in the cortical region.[31] Abnormalities in blood vessels of the brain(Arteriovenous malformation) can also cause epilepsy.[3] In babies and children, congenital brain abnormalities, such as lissencephaly or polymicrogyria, will also result in epilepsy.[3][32] Hypoxic-ischemic encephalopathy in newborns will also predispose the newborn to epilepsy. [33]
Strokes, brain bleeds, and traumatic brain injury can all also lead to epilepsy if seizures re-occur. If the first seizure occurs more than 7 days following a stroke, there is a higher chance of the person developing epilepsy.[28] Post-stroke epilepsy accounts for 30%-50% of new epilepsy cases.[28] This is also the case for traumatic brain injury, with 80% of people with late posttraumatic seizures having another seizure occur, classifying it as epilepsy.[30]
Infections of newborns that occur while before or during birth, such as herpes simplex virus, rubella, and cytomegalovirus, all carry a risk of causing epilepsy.[34] Infection with the pork tapeworm, which can cause neurocysticercosis, is the cause of up to half of epilepsy cases in areas of the world where the parasite is common.[34][35] Meningitis and encephalitis also carry the risk of causing long-term epilepsy as well.[3][34]
During childhood, well-defined epilepsy syndromes are generally seen. Examples include Dravet Syndrome, Lennox-Gastaut Syndrome, and Juvenile Myoclonic Epilepsy.[3]
Neurons function by either being excited or inhibited.[36] Excited neurons fire electrical charges while inhibited neurons are prevented from firing.[36] The balance of the two maintains our central nervous system.[36] In those with seizures, neurons are both hyperexcitable and hypersynchronous, where many neurons fire numerously at the same time.[37] This may be due to an imbalance of excitation and inhibition of neurons.[38][39][37]
γ-aminobutyric acid (GABA) and Glutamate are chemicals called neurotransmitters that work by opening or closing ion channels on neurons to cause inhibition or excitability.[39][40] GABA serves to inhibit neurons from firing. It has been found to be decreased in epilepsy patients.[39][38] This may explain the lack of inhibition of neurons resulting in seizures.[39][38] Glutamate serves to excite neurons into firing when appropriate.[39] It was found to be increased in those with epilepsy.[39][38] This is a possible mechanism for why there is hyper-excitability of neurons in seizures.
Seizures that occur after brain injury may be due to the brain adapting to injury (neuroplasticity).[41] This process is known as epileptogenesis.[42] There is loss of inhibitory neurons because they die due to the injury.[42][41] The brain may also adapt and make new neuron connections that may be hyper-excitatory.[42][41]
Brief seizures, such as absence seizures lasting 5-10 seconds, do not cause observable brain damage.[43] More prolonged seizures have a higher risk of neuronal death.[43] Prolonged and recurrent seizures, such as status epilepticus, typically cause brain damage.[43] Scarring of brain tissue (gliosis), neuronal death, and shrinking of areas of the brain (atrophy) are linked to recurrent seizures.[43][44] These changes may lead to the development of epilepsy.[44]
Seizures may be divided into provoked and unprovoked.[6] Provoked seizures may also be known as "acute symptomatic seizures" or "reactive seizures".[6] Unprovoked seizures may also be known as "reflex seizures".[6] Depending on the presumed cause blood tests and lumbar puncture may be useful.[7] Hypoglycemia may cause seizures and should be ruled out. An electroencephalogram and brain imaging with CT scan or MRI scan is recommended in the work-up of seizures not associated with a fever.[7][45]
Seizure types are organized by whether the source of the seizure is localized (focal seizures) or distributed (generalized seizures) within the brain.[46] Generalized seizures are divided according to the effect on the body and include tonic-clonic (grand mal), absence (petit mal), myoclonic, clonic, tonic, and atonic seizures.[46][47] Some seizures such as epileptic spasms are of an unknown type.[46]
Focal seizures (previously called partial seizures)[48] are divided into simple partial or complex partial seizure.[46] Current practice no longer recommends this, and instead prefers to describe what occurs during a seizure.[46]
The classification of seizures can also be made according to dynamical criteria, observable in electrophysiological measurements. It is a classification according to their type of onset and offset.[49][50]
Most people are in a postictal state (drowsy or confused) following a seizure. They may show signs of other injuries. A bite mark on the side of the tongue helps confirm a seizure when present, but only a third of people who have had a seizure have such a bite.[51] When present in people thought to have had a seizure, this physical sign tentatively increases the likelihood that a seizure was the cause.[52]
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. In certain situations it may be useful to prefer the EEG while sleeping or sleep deprived.[53]
Diagnostic imaging by CT scan and MRI is recommended after a first non-febrile seizure to detect structural problems inside the brain.[53] MRI is generally a better imaging test except when intracranial bleeding is suspected.[7] Imaging may be done at a later point in time in those who return to their normal selves while in the emergency room.[7] If a person has a previous diagnosis of epilepsy with previous imaging repeat imaging is not usually needed with subsequent seizures.[53]
In adults, testing electrolytes, blood glucose and calcium levels is important to rule these out as causes, as is an electrocardiogram.[53] A lumbar puncture may be useful to diagnose a central nervous system infection but is not routinely needed.[7] Routine antiseizure medical levels in the blood are not required in adults or children.[53] In children additional tests may be required.[53]
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.[54][55] Serum prolactin level is less useful for detecting partial seizures.[56] If it is normal an epileptic seizure is still possible[55] and a serum prolactin does not separate epileptic seizures from syncope.[57] It is not recommended as a routine part of diagnosis epilepsy.[53]
Differentiating an epileptic seizure from other conditions such as syncope can be difficult.[58] Other possible conditions that can mimic a seizure include decerebrate posturing, psychogenic seizures, tetanus, dystonia, migraine headaches, and strychnine poisoning.[58] In addition, 5% of people with a positive tilt table test may have seizure-like activity that seems due to cerebral hypoxia.[59] Convulsions may occur due to psychological reasons and this is known as a psychogenic non-epileptic seizure. Non-epileptic seizures may also occur due to a number of other reasons.
A number of measures have been attempted to prevent seizures in those at risk. Following traumatic brain injury anticonvulsants decrease the risk of early seizures but not late seizures.[60]
In those with a history of febrile seizures, some medications (both antipyretics and anticonvulsants) have been found effective for reducing reoccurrence, however due to the frequency of adverse effects and the benign nature of febrile seizures the decision to use medication should be weighted carefully against potential negative effects.[61]
There is no clear evidence that antiepileptic drugs are effective or not effective at preventing seizures following a craniotomy,[62] following subdural hematoma,[63] after a stroke,[64][65] or after subarachnoid haemorrhage,[66] for both people who have had a previous seizure, and those who have not.
Potentially sharp or dangerous objects should be moved from the area around a person experiencing a seizure 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, or two or more seizures occurring within the time of five minutes is a medical emergency known as status epilepticus.[67][68] Because of a common misconception that a person experiencing a seizure can "swallow their own tongue", bystanders might attempt to force objects into the mouth; this deed may cause choking.[69]
Treatments of a person that is actively seizing follows a progression from initial response, through first line, second line, and third line treatments.[70] The initial response involves ensuring the person is protected from potential harms (such as nearby objects) and managing their airway, breathing, and circulation.[70] Airway management should include placing the person on their side, known as the recovery position, to prevent them from choking.[70] If they are unable to breathe because something is blocking their airway, they may require treatments to open their airway.[70]
The first line medication for an actively seizing person is a benzodiazepine, with most guidelines recommending lorazepam.[45][71] Diazepam and midazolam are alternatives. This may be repeated if there is no effect after 10 minutes.[45] If there is no effect after two doses, barbiturates or propofol may be used.[45]
Second-line therapy for adults is phenytoin or fosphenytoin and phenobarbital for children.[72][page needed] Third-line medications include phenytoin for children and phenobarbital for adults.[72][page needed]
Ongoing anti-epileptic medications are not typically recommended after a first seizure except in those with structural lesions in the brain.[45] They are generally recommended after a second one has occurred.[45] Approximately 70% of people can obtain full control with continuous use of medication.[73] Typically one type of anticonvulsant is preferred. Following a first seizure, while immediate treatment with an anti-seizure drug lowers the probability of seizure recurrence up to five years it does not change the risk of death and there are potential side effects.[74]
In seizures related to toxins, up to two doses of benzodiazepines should be used.[75] If this is not effective pyridoxine is recommended.[75] Phenytoin should generally not be used.[75]
There is a lack of evidence for preventive anti-epileptic medications in the management of seizures related to intracranial venous thrombosis.[65]
In severe cases, brain surgery can be a treatment option for epilepsy.[76] See also Epilepsy Surgery.
Helmets may be used to provide protection to the head during a seizure. Some claim that seizure response dogs, a form of service dog, can predict seizures.[77] Evidence for this, however, is poor.[77] At present there is not enough evidence to support the use of cannabis for the management of seizures, although this is an ongoing area of research.[78][79] There is low quality evidence that a ketogenic diet may help in those who have epilepsy and is reasonable in those who do not improve following typical treatments.[80]
Following a first seizure, the risk of more seizures in the next two years is around 40%.[15][81] The greatest predictors of more seizures are problems either on the electroencephalogram or on imaging of the brain.[7] In adults, after 6 months of being seizure-free after a first seizure, the risk of a subsequent seizure in the next year is less than 20% regardless of treatment.[82] Up to 7% of seizures that present to the emergency department (ER) are in status epilepticus.[45] In those with a status epilepticus, mortality is between 10% and 40%.[58] Those who have a seizure that is provoked (occurring close in time to an acute brain event or toxic exposure) have a low risk of re-occurrence, but have a higher risk of death compared to those with epilepsy.[83]
Approximately 8–10% of people will experience an epileptic seizure during their lifetime.[84] In adults, the risk of seizure recurrence within the five years following a new-onset seizure is 35%; the risk rises to 75% in persons who have had a second seizure.[84] In children, the risk of seizure recurrence within the five years following a single unprovoked seizure is about 50%; the risk rises to about 80% after two unprovoked seizures.[85] In the United States in 2011, seizures resulted in an estimated 1.6 million emergency department visits; approximately 400,000 of these visits were for new-onset seizures.[84] The exact incidence of epileptic seizures in low-income and middle-income countries is unknown, however it probably exceeds that in high-income countries.[86] This may be due to increased risks of traffic accidents, birth injuries, and malaria and other parasitic infections.[86]
Epileptic seizures were first described in an Akkadian text from 2000 B.C.[87] Early reports of epilepsy often saw seizures and convulsions as the work of "evil spirits".[88] The perception of epilepsy, however, began to change in the time of Ancient Greek medicine. The term "epilepsy" itself is a Greek word, which is derived from the verb "epilambanein", meaning "to seize, possess, or afflict".[87] Although the Ancient Greeks referred to epilepsy as the "sacred disease", this perception of epilepsy as a "spiritual" disease was challenged by Hippocrates in his work On the Sacred Disease, who proposed that the source of epilepsy was from natural causes rather than supernatural ones.[88]
Early surgical treatment of epilepsy was primitive in Ancient Greek, Roman and Egyptian medicine.[89] The 19th century saw the rise of targeted surgery for the treatment of epileptic seizures, beginning in 1886 with localized resections performed by Sir Victor Horsley, a neurosurgeon in London.[88] Another advancement was that of the development by the Montreal procedure by Canadian neurosurgeon Wilder Penfield, which involved use of electrical stimulation among conscious patients to more accurately identify and resect the epileptic areas in the brain.[88]
Seizures result in direct economic costs of about one billion dollars in the United States.[7] Epilepsy results in economic costs in Europe of around €15.5 billion in 2004.[48] In India, epilepsy is estimated to result in costs of US$1.7 billion or 0.5% of the GDP.[73] They make up about 1% of emergency department visits (2% for emergency departments for children) in the United States.[90]
Many areas of the world require a minimum of six months from the last seizure before people can drive a vehicle.[7]
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.[91]
Two promising areas include gene therapy,[92] and seizure detection and seizure prediction.[93]
Gene therapy for epilepsy consists of employing vectors to deliver pieces of genetic material to areas of the brain involved in seizure onset.[92]
Seizure prediction is a special case of seizure detection in which the developed systems is able to issue a warning before the clinical onset of the epileptic seizure.[91][93]
Computational neuroscience has been able to bring a new point of view on the seizures by considering the dynamical aspects.[50]
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