|Classification and external resources|
Generalized 3 Hz spike and wave discharges in EEG
|ICD-10||G40, P90, R56|
Epileptic seizures are brief episodes of "abnormal excessive or synchronous neuronal activity in the brain".. The term fit is also sometimes used to describe an epileptic seizure although the term is considered potentially derogatory.
The outward effect can be as dramatic as a wild thrashing movement (tonic-clonic seizure) or as mild as a brief loss of awareness (absence seizure). It can manifest as an alteration in mental state, tonic or clonic movements, convulsions, and various other psychic symptoms (such as déjà vu or jamais vu). Sometimes it is not accompanied by convulsions but a full body "slump", where the person simply will lose body control and slump to the ground. The medical syndrome of recurrent, unprovoked seizures is termed epilepsy, but seizures can occur in people who do not have epilepsy. For more information, see non-epileptic seizure.
Epilepsy affects more than 50 million people worldwide, nearly 80% of whom live in developing countries. About 4% of all people will have an unprovoked seizure by the age of 80 and the chance of experiencing a second seizure is between 30% and 50%. Treatment may reduce the chance of a second one by as much as half. Most single episode seizures are managed by primary care physicians (emergency or general practitioners), whereas investigation and management of ongoing epilepsy is usually done by neurologists. Difficult-to-manage epilepsy may require consultation with an epileptologist, a neurologist with an interest in epilepsy.
Clinicians organize different types of seizure according to whether the source of the seizure within the brain is localized (partial- or focal-onset seizures) or distributed (generalized seizures). Partial seizures are further divided on the extent to which consciousness is affected (simple partial seizures and complex partial seizures). Simple partial seizures do not cause a loss in consciousness, but can cause a change in consciousness. A complex partial seizure causes loss of consciousness. Partial seizures have a specific focus, which is the source of the irritation. This is commonly a scarred area of the brain, often scarred due to events such as a brain injury or a blood vessel. A partial seizure may spread within the brain, a process known as secondary generalization. Generalized seizures are divided according to the effect on the body, but all involve loss of consciousness. These include absence, myoclonic, clonic, tonic, tonic–clonic, and atonic seizures. Generalized seizures are more widespread than partial seizures. Unlike partial seizures, generalized seizures do not always have a focal point. In those cases the point of origin is unknown. A mixed seizure is defined as the existence of both generalized and partial seizures in the same patient.
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.
Signs and symptoms
The signs and symptoms of seizures vary depending on the type. Seizures may cause involuntary changes in body movement or function, sensation, awareness, or behavior. Seizures are often associated with a sudden and involuntary contraction of a group of muscles and loss of consciousness. However, a seizure can also be as subtle as a fleeting numbness of a part of the body, a brief or long term loss of memory, visual changes, sensing/discharging of an unpleasant odor, a strange epigastric sensation, or a sensation of fear and total state of confusion. A seizure can last from a few seconds to status epilepticus, a continuous group of seizures that is often life-threatening without immediate intervention. Therefore seizures are typically classified as motor, sensory, autonomic, emotional or cognitive. After the active portion of a seizure, there is typically a period referred to as postictal before a normal level of consciousness returns.
In some cases, the full onset of a seizure event is preceded by some of the sensations described above, called vertiginous epilepsy. These sensations can serve as a warning to that a generalized tonic–clonic seizure is about to occur. These warning sensations are cumulatively called an aura and are due to a focal seizure.
Some patients can tell when a seizure is about to happen. Some symptoms experienced by the person before a seizure may include dizziness, lightheadedness, tightening of the chest, and some experience things in slow-motion just prior to the seizure. Symptoms experienced by a person during a seizure depend on where in the brain the disturbance in electrical activity occurs. Partial and frontal seizures and focal epileptic discharges tend to happen more during sleep than during wakefulness. In contrast, psychogenic nonepileptic seizures are rare between midnight and 6 am and never occur during sleep. Generalized epilepsy but not focal epilepsy is higher in the morning probably reflecting a diurnal variation in cortical excitability. A person having a tonic–clonic seizure may cry out, lose consciousness and fall to the ground, and convulse, often violently. A person having a complex partial seizure may appear confused or dazed and will not be able to respond to questions or direction. Some people have seizures that are not noticeable to others. Sometimes, the only clue that a person is having an absence seizure is rapid blinking, extreme confusion for a few seconds or sometimes into hours.
Unprovoked seizures are often associated with epilepsy and related seizure disorders.
Causes of provoked seizures include:
- sleep deprivation
- cavernoma or cavernous malformation is a treatable medical condition that can cause seizures, headaches, and brain hemorrhages. An MRI can quickly confirm or reject this as a cause.
- arteriovenous malformation (AVM) is a treatable medical condition that can cause seizures, headaches, and brain hemorrhages.
- head injury may cause non-epileptic post-traumatic seizures or post-traumatic epilepsy, in which the seizures chronically recur.
- drug overdose or toxicity, for example aminophylline or local anaesthetics
- normal doses of certain drugs that lower the seizure threshold, such as tricyclic antidepressants
- infection, such as encephalitis or meningitis
- fever leading to febrile convulsions (but see above)
- metabolic disturbances, such as hypoglycaemia, hyponatremia or hypoxia
- withdrawal from drugs (anticonvulsants, antidepressants, and sedatives such as alcohol, barbiturates, and benzodiazepines,)
- space-occupying lesions in the brain (abscesses, tumours). In people with brain tumours, the frequency of epilepsy depends on the location of the tumor in the cortical region.
- seizures during (or shortly after) pregnancy can be a sign of eclampsia.
- seizures in a person with hydrocephalus may indicate severe shunt 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
- multiple sclerosis sufferers may rarely experience seizures
- parasitic infections such as cerebral malaria
Some medications produce an increased risk of seizures and electroconvulsive therapy (ECT) deliberately sets out to induce a seizure for the treatment of major depression. Many seizures have unknown causes.
Seizures which are provoked are not associated with epilepsy, and people who experience such seizures are normally not diagnosed with epilepsy. However, the seizures described above resemble those of epilepsy both outwardly, and on EEG testing.
Seizures can occur after a subject witnesses a traumatic event. This type of seizure is known as a psychogenic non-epileptic seizure and is related to posttraumatic stress disorder.
Only about 25 percent of people who have a seizure or develop status epilepticus have epilepsy. It is important to distinguish primary epileptic seizures from secondary causes. Blood tests, lumbar puncture or toxicology screening can be helpful in specific circumstances suggestive of an underlying cause like alcohol or benzodiazepine withdrawal, meningitis or drug overdose, but there is insufficient evidence to support their routine use in the work-up of an adult with an apparently unprovoked first seizure. A 2007 review recommends an electroencephalogram and brain imaging with CT scan or MRI scan in the work-up. MRI is more sensitive in a first apparently unprovoked seizure.
Most patients are in a postictal state following a seizure. In this state they are drowsy and often confused. There may be signs of other injuries. A small study found that finding 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 (sensitivity of 24%), the finding was very specific for seizures, with only 1% due to other causes (specificity of 99%).
A high prolactin levels in blood draw within the first 20 minutes following a seizure are useful to confirm a epileptic seizure as opposed to psychogenic non-epileptic seizure. Serum prolactin level is less use for detecting partial seizures. If it is normal however an epileptic seizure is still possible.
"Serum prolactin assay does not distinguish epileptic seizures from syncope (Level B).
An isolated abnormal electrical activity recorded by an electroencephalography examination without a clinical presentation is called subclinical seizure. They can identify background epileptogenic activity, as well as help identify causes of seizures.
Determining the underlying cause
Additional diagnostic methods include CT Scanning and MRI imaging or angiography. These may show structural lesions within the brain and heart, but the majority of those with epilepsy show nothing unusual.
As seizures have a broad differential diagnosis, it is common for patients to be simultaneously investigated for cardiac and endocrine causes. Checking glucose levels, for example, is a mandatory action in the management of seizures as hypoglycemia may cause seizures, and failure to administer glucose would be harmful to the patient. Other causes typically considered are syncope and cardiac arrhythmias, and occasionally panic attacks and cataplexy. In addition, 5% of patients with a positive tilt table test may have seizure-like activity that seems to be due to cerebral hypoxia. For more information, see non-epileptic seizures.
Differentiating an epileptic seizure from other conditions such as syncope can be difficult. Other possible conditions that can mimic a seizure include: decerebrate posturing, psychogenic seizures, dystonia, migraine headaches, and strychnine poisoning.
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. Caregivers may carry medicine.
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 has occurred or those with structural lesions in the brain. However, in severe cases where patients experience frequent unpredictable seizures everyday, the use of anti-epileptic drugs (AEDs) are recommended to reduce the likelihood and duration of seizures. Approximately 70% of the patients could have the seizures fully under control with continuous use of medication. The National Institute of Health and Clinical Excellence (NICE) suggests patients taking only one type of AEDs at a time.
A seizure response dog can be trained to summon help or ensure personal safety when a seizure occurs. These are not suitable for everybody. Rarely, a dog may develop the ability to sense a seizure before it occurs. Helmets may be used to provide protection of the head during a seizure.
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%.
It is believed that around 10% of people who live to 80 years old have at least one epileptic seizure. About 7 per 1000 people in the United States have a seizure in a given year. Rates are highest in those less than 1 year of age and greater than 55.
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