|Classification and external resources|
Generalized 3 Hz spike and wave discharges in EEG
|ICD-10||G40, P90, R56|
Epileptic seizures (colloquially a fit) are brief episodes of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can vary from wild thrashing movement (tonic-clonic seizure) to as mild as a brief loss of awareness (absence seizure). The syndrome of recurrent, unprovoked seizures is termed epilepsy, but seizures can occur in people who do not have epilepsy. Additionally there are a number of conditions that look like seizures but are not.
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 affected, nearly 80%, live in developing countries.
- 1 Signs and symptoms
- 2 Causes
- 3 Diagnosis
- 4 Prevention
- 5 Management
- 6 Prognosis
- 7 Epidemiology
- 8 History
- 9 Society and culture
- 10 Research
- 11 References
- 12 External links
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. Therefore seizures are typically classified as motor, sensory, autonomic, emotional or cognitive.
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.
In some cases, the full onset of a seizure is preceded by certain sensations, in which case it is called vertiginous epilepsy. These sensations may include: dizziness, lightheadedness, tightening of the chest, or the experience of things in slow-motion. These sensations can serve as a warning that a generalizedtonic–clonic seizure is about to occur. These warning sensations are cumulatively called an aura and are due to a focal seizure.
Different causes of seizures are common in certain age groups.
- During the neonatal period and early infancy the most common causes include hypoxic ischemic encephalopathy, central nervous system (CNS) infections, trauma, congenital CNS abnormalities, andmetabolic disorders.
- During late infancy and early childhood, febrile seizures are fairly common. These may be caused by many different things, some thought to be things such as CNS infections and trauma.
- During childhood, well-defined epilepsy syndromes are generally seen.
- During adolescence and adulthood, the causes are more likely to be secondary to any CNS lesion. Further, idiopathic epilepsy is less common. Other causes associated with these age groups are stress, trauma, CNS infections, brain tumors, illicit drug use and alcohol withdrawal.
- In older adults, cerebrovascular disease is a very common cause. Other causes are CNS tumors, head trauma, and other degenerative diseases that are common in the older age group, such as dementia.
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 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.
Convulsions may occur do to psychological reasons and this is known as a psychogenic non-epileptic seizure. In this situation the EEG is normal.
It is important to distinguish primary seizures from secondary causes. Depending on the presumed cause blood tests and/or lumbar puncture may be useful. 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.
Seizure are organized 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.
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.
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 does not separate epileptic seizures from syncope.
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.
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. MRI is generally more sensitive in a first apparently unprovoked seizure except were bleeding is suspected. Imaging may be done at a later point in time in those who return to there normal selves while in the emergency room.
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. In addition, 5% of people 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.
In those with a history of febrile seizures medications (both antipyretics and anticonvulsants) have not been found effective for prevention; however, some appear to be associated with harm. In those without a history of seizures and a subdural hematoma the evidence is unclear regarding a benefit versus harm from using anticonvulsants. This is also true following a craniotomy as well as after stroke, intracranial venous thrombosis, and subarachnoid haemorrhage both in those who have and have not had 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.
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.
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%.
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.
Society and culture
Seizures result in direct economic costs of about one billion dollars in the United States. Many areas of the world require there to be a minimum of six month 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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