Epilepsy (from the Ancient Greek verb ἐπιλαμβάνειν meaning “to seize, possess, or afflict”) is a group of neurological disorders characterized by epileptic seizures. Epileptic seizures are episodes that can vary from brief and nearly undetectable to long periods of vigorous shaking. In epilepsy, seizures tend to recur, and have no immediate underlying cause while seizures that occur due to a specific cause are not deemed to represent epilepsy.
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. Epileptic seizures are the result of excessive and abnormal cortical nerve cell activity in the brain. 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. This may be done by doing imaging of the brain and blood tests. Epilepsy can often be confirmed with an electroencephalogram (EEG) but a normal test does not rule out the disease.
Seizures are controllable with medication in about 70% of cases. 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 (65 million) have epilepsy, and nearly 80% of cases occur in developing countries. Epilepsy becomes more common as people age. In the developed world, onset of new cases occurs most frequently in infants and the elderly; in the developing world this is in older children and young adults, due to differences in the frequency of the underlying causes. 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%. In many areas of the world those with epilepsy either have their ability to drive restricted or disallowed, but most are able to return to driving after a period of time without seizures.
There is evidence that epileptic seizure are usually not a random event. Seizures are often brought on by factors such as lack of sleep, stress or flickering light among others. The term seizure threshold is used to indicate the amount of stimulus necessary to bring about a seizure. Seizure threshold is lowered in epilepsy.
The exact mechanism of epilepsy itself is unknown. Some; however, is known about both the cellular and network mechanisms of epilepsy. However, it is unknown under which circumstances the brain shifts into the activity of a seizure with its excessive synchronization.
Epilepsy can have both genetic and acquired causes, with interaction of these factors in many cases. Established acquired causes include serious brain trauma, stroke, tumours and problems in the brain as a result of a previous infective. In about 60% of cases the cause is unknown. Epilepsies caused by genetic, congenital, or developmental conditions are more common among younger people, while brain tumors and strokes are more likely in older people.
Seizures may also occur as a consequence of other health problems; if they occur right around a specific cause, such as a stroke, head injury, toxic ingestion or metabolic problem, they are known as acute symptomatic seizures and are in the broader classification of seizure-related disorders rather than epilepsy itself.
Signs and symptoms
Epilepsy is characterized by a long-term risk of recurrent seizures. These seizures may present in several ways depending on the part of the brain involved and the person’s age.
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.
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.
While many cases are not preventable, efforts to reduce head injuries, provide good care around the time of birth, and reduce environmental parasites such as the pork tapeworm may be effective. Efforts in one part of Central America to decrease rates of pork tapeworm resulted in a 50% decrease in new cases of epilepsy.
Epilepsy is usually treated with daily medication once a second seizure has occurred, but for those at high risk, medication may be started after the first seizure. In some cases, a special diet, the implantation of a neurostimulator, or neurosurgery may be required.
Rolling a person with an active tonic-clonic seizure onto their side and into the recovery position helps prevent fluids from getting into the lungs. Putting fingers, a bite block or tongue depressor in the mouth is not recommended as it might make the person vomit or result in the rescuer being bitten. Efforts should be taken to prevent further self-injury. Spinal precautions are generally not needed.
If a seizure lasts longer than 5 minutes or if there are more than two seizures in an hour without a return to normal between them it is considered a medical emergency known as status epilepticus. This may require medical help to keep the airway open and protected; a nasopharyngeal airway may be useful for this. At home the recommended initial medication for seizure of a long duration is midazolam placed in the mouth. Diazepam may also be used rectally. In hospital, intravenous lorazepam is preferred. If two doses of benzodiazepines are not effective, other medications such as phenytoin are recommended. Convulsive status epilepticus that does not respond to initial treatment typically requires admission to the intensive care unit and treatment with stronger agents such as thiopentone or propofol.
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