A transient seizure or fit usually associated with a short-lived disturbance of consciousness. It stems from a synchronous high-voltage electrical discharge from groups of neurones in the brain. The disorder takes several forms, which include loss of consciousness with generalized convulsions (grand mal), short periods of loss of consciousness in which patients simply stop what they are doing and look blank (absence or drop attacks, or petit mal), seizures with involuntary movements of only part of the body, such as a limb (Jacksonian epilepsy), and short-lived sensations of smell and smacking of the lips (temporal lobe epilepsy). The majority of cases do not have an obvious cause, but in some individuals seizures follow organic damage to the brain (eg from trauma or tumour), or metabolic disturbances (eg diabetes and kidney failure). Electroencephalography is used in the diagnosis.
Epilepsy (sometimes referred to as a seizure disorder) is a common chronic neurological condition that is characterized by recurrent unprovoked epileptic seizures. These seizures are transient signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Epilepsy is usually controlled, but not cured, with medication – although surgery may be considered in difficult cases. Not all epilepsy syndromes are lifelong, for example some are confined to particular stages of childhood.
Classification
Epilepsies are classified five ways:
By their first cause (or etiology). By the observable manifestations of the seizures, known as "semiology." By the location in the brain where the seizures originate. By the event that triggers the seizures, as in primary reading epilepsy.In 1981, the International League Against Epilepsy (ILAE) proposed a classification scheme for individual seizures that remains in common use. In 1989, the ILAE proposed a classification scheme for epilepsies and epileptic syndromes. Since 1997, the ILAE have been working on a new scheme that has five axes: ictal phenomenon, seizure type, syndrome, etiology and impairment.
Diagnosis
The diagnosis of epilepsy requires the presence of recurrent, unprovoked seizures; EEG, brain MRI, SPECT, PET, and magnetoencephalography may be useful to discover an etiology for the epilepsy, discover the affected brain region, or classify the epileptic syndrome, but these studies are not useful in making the initial diagnosis.
Long-term video-EEG monitoring for epilepsy is the gold standard for diagnosis, but it is not routinely employed owing to its high cost, low availability and inconvenience. These non-epileptic seizures can be hard to differentiate and may lead to misdiagnosis.
Epilepsy covers conditions with different aetiologies, natural histories and prognoses, each requiring different management strategies. A full medical diagnosis requires a definite categorisation of seizure and syndrome types.
Causes
The cause of an individual's epilepsy can be divided into two categories: symptomatic and idiopathic. Symptomatic epilepsies originate due to some structural or metabolic abnormality in the brain. This may be the result of:
genetic conditions such as tuberous sclerosis and ring chromosome 20 syndrome complications during pregnancy or birth stroke head injury neurosurgical operations bacterial or viral encephalitis parasitical infection alcoholThe term cryptogenic is used to describe epilepsy where the cause is suspected to be symptomatic but the underlying illness or damage has not been identified. No other condition has been implicated as the cause of the epilepsy. Idiopathic epilepsies are often but not exclusively genetic and generalised - for example Juvenile Absence Epilepsy.
Triggers
The diagnosis of epilepsy requires that the seizures be "unprovoked", with the implication that the provocant is assumed to be something obviously harmful. However, in some epilepsy syndromes the provocant can reasonably be considered to be part of normal daily life. This last provocant is a special type of reflex epilepsy called photosensitive epilepsy. Although assumed to be a common trigger for epilepsy, amongst both patients and the public, only around 5% of people with epilepsy are affected by flickering lights.
Certain circumstances can lead to an increased likelihood of seizures in someone with epilepsy or in certain syndromes.
Seizure types
Seizure types are organised firstly according to whether the source of the seizure within the brain is localised (partial or focal onset seizures) or distributed (generalised seizures). Partial seizures are further divided on the extent to which consciousness is affected. If it is unaffected, then it is a simple partial seizure; otherwise it is a complex partial seizure. A partial seizure may spread within the brain - a process known as secondary generalisation. Generalised seizures are divided according to the effect on the body but all involve loss of consciousness. These include absence (petit mal), myoclonic, clonic, tonic, tonic-clonic (grand mal) and atonic seizures.
Seizure syndromes
There are many different epilepsy syndromes, each presenting with its own unique combination of seizure type, typical age of onset, EEG findings, treatment, and prognosis. Below are some common seizure syndromes:
Infantile spasms (West syndrome) is associated with brain development abnormalities, tuberous sclerosis, and perinatal insults to the brain. The typical seizures are characterized by sudden flexor and extensor spasms of head, trunk, and extremities. The first line treatment for these patients is adrenocorticotropic hormone (ACTH or corticotropin) since traditional antiepileptic drugs generally cannot adequately control seizure activity. Vigabatrin is also used in many countries, and is particularly effective when tuberous sclerosis is the cause of seizures. These patients have recurrent absence seizures that can occur hundreds of times a day. A subset of these patients will also develop generalized tonic-clonic seizures. First line treatment for pure absence seizures is ethosuximide. If patients do not respond or have mixed seizures along with their absence seizures, then valproic acid can be used. Benign focal epilepsy of childhood (Benign Rolandic epilepsy) begins in children between the ages of 4 and 13 years. Apart from their seizure disorder, these patients are otherwise normal. Seizures occur at night and sleep promotes secondary generalization. As such, parents only report generalized seizures because focal manifestations are often subtle and go unnoticed. Between seizures, patients have a stereotyped EEG pattern that includes di- or triphasic sharp waves over the central-midtemporal (Rolandic) regions. Prognosis is uniformly good with seizures disappearing by adolescence. The seizures are morning myoclonic jerks often with generalized tonic-clonic seizures that occur just after waking. 'Petit mal' or absence seizures are less common in cases of JME, but are known to occur more often in young girls. Interestingly, these patients are often first diagnosed when they have their first generalized tonic-clonic seizure later in life when they experience sleep deprivation (e.g., freshman year in college after staying up late to study for exams). This condition is lifelong, thus patients must be taught appropriate sleep hygiene to prevent generalized tonic-clonic seizures. The severity of JME varies from person to person - some will experience full blown tonic-clonic seizures regularly, others will suffer only under sufficient stress from lack of sleep and intoxication. Temporal lobe epilepsy is the most common epilepsy of adults. Seizures begin in late childhood and adolescence. There is an association with febrile seizures in childhood, and some studies have shown herpes simplex virus (HSV) DNA in these regions, suggesting that perhaps this epilepsy has an infectious etiology. Most of these patients have complex partial seizures sometimes preceded by an aura. Frontal lobe epilepsy Lennox-Gastaut syndrome Occipital lobe epilepsyTreatment
Epilepsy is usually treated with medication prescribed by a physician; primary caregivers, neurologists, and neurosurgeons all frequently care for people with epilepsy. Neurosurgical operations for epilepsy can be palliative, reducing the frequency or severity of seizures;
Responding to a seizure
In most cases, the proper emergency response to a generalized tonic-clonic epileptic seizure is simply to prevent the patient from self-injury by moving him or her away from sharp edges, placing something soft beneath the head, and carefully rolling the person into the recovery position to avoid asphyxiation. In some cases the person may seem to start snoring loudly following a seizure, before coming to. If a seizure lasts longer than 5 minutes, or if the seizures begin coming in 'waves' one after the other - then Emergency Medical Services should be contacted immediately. Prolonged seizures may develop into status epilepticus, a dangerous condition requiring hospitalization and emergency treatment.
Objects should never be placed in a person's mouth by anybody - including paramedics - during a seizure as this could result in serious injury to either party. Despite common folklore, it is not possible for a person to swallow their own tongue during a seizure.
After a seizure, it is typical for a person to be exhausted and confused. Often the person is not immediately aware that they have just had a seizure. Many patients will sleep deeply for a few hours after a seizure - this is common for those having just experienced a more violent type of seizure such as a tonic-clonic. In about 50% of people with epilepsy, headaches may occur after a seizure.
It is helpful if those present at the time of a seizure make note of how long and how severe the seizure was. It is also helpful to note any mannerisms displayed during the seizure. Any observed behaviors, when relayed to a neurologist, may be of help in diagnosing the type of seizure which occured.
Pharmacologic treatment
Some medications can be taken daily in order to prevent seizures altogether or reduce the frequency of their occurrence.
Some people with epilepsy will experience a complete remission when treated with an anticonvulsant medication. The general strategy is to increase the medication dose until either the seizures are controlled, or until dose-limiting side effects appear; For example, therapeutic doses (the dose at which seizures are controlled and side effects are minimal and tolerable) may vary widely from among patients. The therapeutic ranges provided by pharmaceutical companies are only ranges and by using blood serum levels and seizures diaries, better seizure control can sometimes be reached. In some cases (such as a seizure flurry) serum levels can be useful to know if the level is very high or very low.
If a person's epilepsy cannot be brought under control after adequate trials of two or three (experts vary here)different drugs, that person's epilepsy is generally said to be 'medically refractory.'
Various drugs may prevent seizures or reduce seizure frequency: these include carbamazepine (common brand name Tegretol), clobazam (Frisium), clonazepam (Klonopin), ethosuximide (Zarontin), felbamate (Felbatol), fosphenytoin (Cerebyx), flurazepam (Dalmane), gabapentin (Neurontin), lamotrigine (Lamictal), levetiracetam (Keppra), oxcarbazepine (Trileptal), mephenytoin (Mesantoin), phenobarbital (Luminal), phenytoin (Dilantin), pregabalin (Lyrica), primidone (Mysoline), sodium valproate (Epilim), tiagabine (Gabitril), topiramate (Topamax), valproate semisodium (Depakote), valproic acid (Depakene, Convulex), and vigabatrin (Sabril).
Other drugs are commonly used to abort an active seizure or interrupt a seizure flurry;
Surgical treatment
Surgical treatment can be an option for epilepsy when an underlying brain abnormality, such as a benign tumor or an area of scar tissue (e.g.
Surgery is usually only offered to patients when their epilepsy has not been controlled by adequate attempts with multiple medications. Resective surgery, as opposed to palliative, successfully eliminates or significantly reduces seizures in about 50-90% of the patients who undergo it (the exact percentage depends on the particulars of the case and surgeon in question.) Many patients decide not to undergo surgery owing to fear or the uncertainty of having a brain operation.
The most common form of resective surgical treatment for epilepsy is to remove the front part of either the right or left temporal lobe. Of the 48 patients, 21 had had no seizures that caused loss of consciousness since the operation. Three others had been free of seizures for at least 19 years. The rest had either never been completely free of seizures or had died between the time of the surgery and commencement of the study.
Palliative surgery for epilepsy is intended to reduce the frequency or severity of seizures. Examples are callosotomy or commissurotomy to prevent seizures from generalizing (spreading to involve the entire brain), which results in a loss of consciousness. It is performed only when the seizures cannot be controlled by other means. Resective surgery can be considered palliative if it is undertaken with the expectation that it will reduce but not eliminate seizures. It is reserved for people suffering from the most catastrophic epilepsies, such as those due to Rasmussen syndrome.
Other treatment
Ketogenic diets may occasionally be effective in controlling some types of epilepsy;
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. Treatment studies have shown that approximately 50% of those treated in this fashion will show significant seizure reduction. The leads attached to the device are implanted either on the brain surface or in the brain area itself and are located close to the area where the seizures are believed to start. When a seizure begins, an electrical shock is delivered to suppress it. The RNS system responds to detected signs that a seizures is about to begin and can record events and allow customized response patterns which may provide a greater degree of seizure control.
A seizure response dog is a form of service dog that is trained to summon help or ensure personal safety when a seizure occurs. Rarely, a dog may develop the ability to sense a seizure before it occurs.
A number of systematic reviews by the Cochrane Collaboration into treatments for epilepsy looked at acupuncture, psychological interventions, vitamins and yoga and found there is no reliable evidence to support the use of these as treatments for epilepsy.
Pathophysiology
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.
One interesting finding in animals is that repeated low-level electrical stimulation to some brain sites can lead to permanent increases in seizure susceptibility: in other words, a permanent decrease in seizure "threshold." Chemical stimulation can also induce seizures; repeated exposures to some pesticides have been shown to induce seizures in both humans and animals.
History and stigma
The word epilepsy is derived from the Greek epilepsia, which in turn can be broken in to epi- (upon) and lepsis (to take hold of, or seizure) In the past, epilepsy was associated with religious experiences and even demonic possession. In ancient times, epilepsy was known as the "Sacred Disease" because people thought that epileptic seizures were a form of attack by demons, or that the visions experienced by persons with epilepsy were sent by the gods. However, in many cultures, persons with epilepsy have been stigmatized, shunned, or even imprisoned; in the Salpêtrière, the birthplace of modern neurology, Jean-Martin Charcot found people with epilepsy side-by-side with the mentally retarded, those with chronic syphilis, and the criminally insane. In Tanzania to this day, as with other parts of Africa epilepsy is associated with possession by evil spirits, witchcraft, or poisoning, and is believed by many to be contagious.
Legal implications
Most people diagnosed with epilepsy are forbidden by their local laws from operating vehicles. Those few whose seizures do not cause impairment of consciousness, or whose seizures only arise from sleep, may be exempt from such restrictions, depending on local laws. There is an ongoing debate in bioethics over who should bear the burden of ensuring that an epilepsy patient does not drive a car or fly an airplane.
In the U.S., people with epilepsy can drive if their seizures are controlled with treatment and they meet the licensing requirements in their state. How long they have to be free of seizures varies in different states, but it is most likely to be between three months and a year.
In the UK, it is the responsibility of the patient to inform the Driver and Vehicle Licensing Agency (DVLA) if they have epilepsy. The DVLA rules are quite complex , but in summary , those continuing to have seizures or who are within 6 months of medication change may have their license revoked. A doctor who becomes aware that a patient with uncontrolled epilepsy is continuing to drive has, after reminding the patient of their responsibility, a duty to break confidentiality and inform the DVLA.
Important investigators of epilepsy
Galen Jean-Martin Charcot John Hughlings Jackson Hans Berger Herbert Jasper Wilder Penfield H. LennoxNotes and references
^ Commission on Epidemiology and Prognosis, International League Against Epilepsy (1993). "Epileptic seizures and epilepsy: definitions proposed by the International League Against Epilepsy (ILAE) and the International Bureau for Epilepsy (IBE).". ^ (2005-09-21) Atlas: Epilepsy care in the world 2005 (PDF), World Health Organization, 3. ^ (1981) "Proposal for revised clinical and electroencephalographic classification of epileptic seizures. (1989) "Proposal for revised classification of epilepsies and epileptic syndromes. A Proposed Diagnostic Scheme For People With Epileptic Seizures And With Epilepsy: Report Of The Ilae Task Force On Classification And Terminology. Seizure Disorders in Dogs and Cats. ^ Morbus sacer in Africa: some religious aspects of epilepsy in traditional cultures. ^ Hippocrates quotes ^ Epilepsy Foundation Driving and You - Can you drive an automobile if you have epilepsy?. ^ Epilepsy Foundation Driver Information by State ^ UK Epilepsy Action: Driving and Epilepsy, I've had a seizure. Information for drivers can be found in Medical Rules - Group 1 Licence Holders ^ UK Epilepsy Action: booklet with further details about driving PDFPatient resources
Epilepsy information and advice from Epilepsy Action. Epilepsy Information Page from the National Institute of Neurological Disorders and Stroke. Information on epilepsy from the National Society for Epilepsy. Pregnancy and Epilepsy and Epilepsy Info from the North Pacific Epilepsy ResearchProfessional resources
International League Against Epilepsy. Seizures and Epilepsy from eMedicine.Lists of organizations
Many organisations provide regional support for those with epilepsy, their families and professionals in the field. International Bureau for Epilepsy (IBE) An umbrella group for various national and regional epilepsy support organisations. The International League Against Epilepsy (ILAE). The Joint Epilepsy Council of the UK and Ireland - The JEC is an umbrella organisation which exists to represent the united voice of a number of UK and Irish based epilepsy charities.
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