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Epilepsy (sometimes referred to as a seizure disorder) is a chronic neurological condition characterized by recurrent unprovoked seizures. The condition is named from the Greek epilepsia ("a taking hold of or seizing"), and has in the past been associated with religious experiences and even demonic possession.
Historically epilepsy was called the Sacred Disease because people thought that epileptic seizures were a form of attack by demons, and that the visions epileptics experienced were sent by the Gods. remarked that epilepsy would be considered divine only until it was understood.
Epileptic seizures are classified both by their patterns of activity in the brain and their effects on behaviour.
In terms of their pattern of activity, seizures may be described as either partial or generalised. Partial seizures only involve a localised part of the brain, whereas generalised seizures involve the entire cortex. The term 'secondary generalisation' may be used to describe a partial seizure that later spreads to the whole of the cortex and becomes generalised.
Partial seizures may be further subdivided into simple and complex seizures. This refers to the effect of such a seizure on consciousness; simple seizures cause no interruption to consciousness (although they may cause sensory distortions or other sensations) whereas complex seizures interrupt consciousness. This does not necessarily mean that the person experiencing this sort of seizure will fall unconscious (like a faint). For example, complex partial seizures may involve the unconscious repetition of simple actions, gestures or verbal utterances.
The effects of partial seizures can be quite dependent on the area of the brain in which they are active. For example, a partial seizure in areas involved in perception may cause a particular sensory experience (for example, the perception of a scent, music or flashes of light) whereas when centred in the motor cortex a partial seizure might cause movement in particular groups of muscles. This type of seizure may also produce particular thoughts or internal visual images or even experiences which may be distinct but not easily described. Seizures centred on the temporal lobes are known to produce mystical or ecstatic experiences in some people. These may result in a misdiagnosis of psychosis or even schizophrenia, if other symptoms of seizure are disregarded and other tests are not performed. Unfortunately for those with epilepsy, anti-psychotic medications prescribed without anti-convulsants in this case can actually lower the seizure threshold further and worsen the symptoms.
In about half of cases of temporal lobe epilepsy, very strong ictal headaches may occur, often misdiagnosed as migraine with aura. However, these headaches may be much more intense, and are sometimes even accompanied by temporary blindness.
When these effects appear as a 'warning sign' before a more serious seizure they are known as an aura and may be the result of a partial seizure which later becomes generalised.
Generalised seizures can be sub-classified into a number of categories, depending on their behavioural effects:
The causes of epilepsy are not known, but some scientists believe that seizures can result from a number of unrelated conditions, including damage resulting from high fever, stroke, toxicity, or electrolyte imbalances. Generalized tonic/clonic seizures may occur in any person under certain circumstances, including fevers and drug overdoses, but these patients are not typically classified as epileptics. Epilepsy connotes that an individual has seizures which recur over time in an unpredictable fashion. In 70% of all cases, there is no cause for epilepsy that is currently detectable at the state of the art. Some claim that it can occur in anyone at any age with no apparent etiological basis. In the other 30% of cases, abnormal electrical activity can be detected in the brain.
The most common ages of onset for epilepsy are for those under the age of 18 and those over the age of 65. It has been estimated that about 4% of the population has some form of epilepsy, but some theorize that the incidence may be much higher in fact.
A significant and measurable decline in cognitive function is known to be associated with epilepsy although it has not been entirely clear to what extent this is due to the epilepsy itself or to the drugs used to treat it. Newer anti-epileptic drugs are considered by some to have less severe cognitive effects than older drugs. On an individual level, a person's reaction to epileptic seizures and/or anti-epileptic drugs may be idiosyncratic so it is sometimes difficult to predict how a particular person might be affected.
Mutations in several genes have been linked to some types of epilepsy. Several genes that code for protein subunits of voltage-gated and ligand-gated ion channels have been associated with forms of generalized epilepsy and infantile seizure syndromes. Several ligand-gated ion channels have been linked to some types of frontal and generalized epilepsies. Epilepsy-related mutations in some non-ion channel genes have also been identified.
Epilepsy is often treated with medication, neurocybernetic prostheses (similar to a heart pacemaker) and occasionally via surgery or specialized diet. In most cases, the proper emergency response to a Generalized Tonic/Clonic epileptic seizure is simply to prevent the patient from injuring themselves by moving him or her away from sharp edges, placing something soft beneath the head, and carefully moving the person onto his or her side to avoid asphyxiation. If the seizure lasts longer than 3-4 minutes, contact Emergency Medical Services immediately, as this may indicate the presence of Status Epilepticus, a potentially fatal condition. One should never place any object in a person's mouth during a seizure as this could result in injury to the victim's mouth. Despite common folklore, it is not possible for a person to swallow the tongue during a seizure.
Various drugs have been discovered that serve to control or limit seizures, including marijuana, carbamazepine (brand name Tegretol), oxcarbazepine (Trileptal), clonazepam (Klonopin), ethosuximide (Zarontin), felbamate (Felbatol), fosphenytoin (Cerebyx), gabapentin (Neurontin), lamotrigine (Lamictal), phenobarbital (Luminal), phenytoin (Dilantin), primidone (Mysoline), tiagabine (Gabitril), topiramate (Topamax), valproate, sodium divalproex (Depakene, Depakote), vigabatrin (Sabril) and levetiracetam (Keppra).
Ketogenic diets have also been found to be effective in controlling some types of epilepsy, although the mechanism behind the effect is not fully understood. Ketogenic diets are high in fat and extremely low in carbohydrates, with intake of fluids often limited. This treatment, originated as early as the 1920s, was largely abandoned with the discovery of modern anti-epileptic drugs, but has enjoyed a return to popularity in recent times. Ketogenic diets are sometimes prescribed in severe cases where drugs have proven ineffective.
Vagus nerve stimulation is a recently developed form of seizure control which uses an implanted electrical device, similar in size, shape and implant location to a heart pacemaker, which connects to the vagus nerve in the neck. Once in place the device can be set to emit electronic pulses to the vagus nerve at pre-set intervals and milliamp levels. Treatment studies have shown that approximately 50% of epileptics treated in this fashion will show significant seizure reduction.
Some sufferers receive a special kind of dog which has the rare talent of sensing the onset of a seizure and are trained to alert the human so they can reach a safe location before their seizure puts them in danger.
There has been some relatively mild controversy over the standards for diagnosis for partial-complex seizures and how these standards are applied in practice, both among some surrealists and in particular as regards Mary Baker Eddy, founder of Christian Science.
In April 2003, the BBC TV science programme "Horizon" featured discussion of research by American neurologist Gregory Holmes indicating that Ellen G. White, spiritual founder of the Seventh-day Adventist Church, may have suffered from temporal lobe epilepsy as a result of brain damage due to an accident suffered at age nine – the epilepsy supposedly being responsible for her powerful religious experiences.
There has also been serious speculation that science fiction author Philip K. Dick suffered from similar seizures; he claimed to have experienced visions on several occasions, that, among other things, reportedly helped him save his infant son from an undiagnosed life-threatening medical condition.
Presently, many popular movies and television shows appear to show characters who experience the sorts of things that might be associated with temporal lobe epilepsy. See, for example, Joan of Arcadia.
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