Epilepsy (from the Ancient Greek verb meaning "to seize, possess, or afflict")[1] is a group of neurological disorders characterized by epileptic seizures.[2][3] Epileptic seizures are episodes that can vary from brief and nearly undetectable to long periods of vigorous shaking.[4] In epilepsy, seizures tend to recur, and have no immediate underlying cause[2] while seizures that occur due to a specific cause are not deemed to represent epilepsy.[5]
The cause of most cases of epilepsy is unknown, although some people develop epilepsy as the result of brain injury, stroke, brain tumor, and drug and alcohol misuse. Genetic mutations are linked to a small proportion of the disease.[6] Epileptic seizures are the result of excessive and abnormal cortical nerve cell activity in the brain.[5] The diagnosis typically involves ruling out other conditions that might cause similar symptoms such as syncope. Additionally it involves determining if any other cause of seizures are present such as alcohol withdrawal or electrolyte problems.[6] This may be done by doing imaging of the brain and blood tests.[6] Epilepsy can often be confirmed with an electroencephalogram (EEG) but a normal test does not rule out the disease.[6]
Seizures are controllable with medication in about 70% of cases.[7] In those whose seizures do not respond to medication, surgery, neurostimulation or dietary changes may be considered. Not all cases of epilepsy are lifelong, and a substantial number of people improve to the point that medication is no longer needed.
About 1% of people worldwide (65million) have epilepsy,[8] and nearly 80% of cases occur in developing countries.[4] Epilepsy becomes more common as people age.[9][10] In the developed world, onset of new cases occurs most frequently in infants and the elderly;[11] in the developing world this is in older children and young adults,[12] due to differences in the frequency of the underlying causes. About 510% of all people will have an unprovoked seizure by the age of 80,[13] and the chance of experiencing a second seizure is between 40 and 50%.[14] In many areas of the world those with epilepsy either have their ability to drive restricted or disallowed,[15] but most are able to return to driving after a period of time without seizures.
Epilepsy is characterized by a long-term risk of recurrent seizures.[16] These seizures may present in several ways depending on the part of the brain involved and the person's age.[16]
The most common type (60%) of seizures are convulsive. Of these, two-thirds begin as focal seizures (which may then become generalized) while one-third begin as generalized seizures. The remaining 40% of seizures are non-convulsive. An example of this type is the absence seizure, which presents as a decreased level of consciousness and usually lasts about 10 seconds.[18][19]
Focal seizures are often preceded by certain experiences, known as an aura.[20] These may include sensory (visual, hearing or smell), psychic, autonomic, or motor phenomena.[18] 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.[21]Automatisms may occur; these are non-consciously generated activities and mostly simple repetitive movements like smacking of the lips or more complex activities such as attempts to pick something up.[21]
There are six main types of generalized seizures: tonic-clonic, tonic, clonic, myoclonic, absence, and atonic seizures. They all involve 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 1030seconds (the tonic phase). A cry may be heard due to contraction of the chest muscles. This is then followed by a shaking of the limbs in unison (clonic phase). Tonic seizures produce constant contractions of the muscles. A person often turns blue as breathing is stopped. In clonic seizures there is shaking of the limbs in unison. After the shaking has stopped it may take 1030minutes for the person to return to normal; this period is called the "postictal phase". Loss of bowel or bladder control may occur during a seizure.[4] The tongue may be bitten at either the tip or on the sides during a seizure.[23] In tonic-clonic seizure, bites to the sides are more common.[23] Tongue bites are also relatively common in psychogenic non-epileptic seizures.[23]
Myoclonic seizures involve spasms of muscles in either a few areas or all over.[24] Absence seizures can be subtle with only a slight turn of the head or eye blinking.[18] The person does not fall over and returns to normal right after it ends.[18] Atonic seizures involve the loss of muscle activity for greater than one second.[21] This typically occurs on both sides of the body.[21]
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