Epilepsy (from the Ancient Greek ἐπιληψία epilēpsía) is a common chronic neurological disorder characterized by recurrent unprovoked seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or synchronous neuronal activity in the brain. About 50 million people worldwide have epilepsy, with almost 90% of these people being in developing countries. Epilepsy is more likely to occur in young children, or people over the age of 65 years, however it can occur at any time. Epilepsy is usually controlled, but not cured, with medication, although surgery may be considered in difficult cases. However, over 30% of people with epilepsy do not have seizure control even with the best available medications. Not all epilepsy syndromes are lifelong – some forms are confined to particular stages of childhood. Epilepsy should not be understood as a single disorder, but rather as syndromic with vastly divergent symptoms but all involving episodic abnormal electrical activity in the brain.
There are over 40 different types of epilepsy, including: Absence seizures, atonic seizures, benign Rolandic epilepsy, childhood absence, clonic seizures, complex partial seizures, frontal lobe epilepsy, Febrile seizures, Infantile spasms, Juvenile Myoclonic Epilepsy, Juvenile Absence Epilepsy, lennox-gastaut syndrom, Landau-Kleffner Syndrome , myoclonic seizures, Mitochondrial Disorders, Progressive Myoclonic Epilepsies, Psychogenic Seizures , Reflex Epilepsy, Rasmussen's Syndrome, Simple Partial seizures, Secondarily Generalized Seizures, Temporal Lobe Epilepsy, Toni-clonic seizures, Tonic seizures, Psychomotor Seizures, Limbic Epilepsy, Partial-Onset Seizures, generalised-onset seizures, Status Epilepticus, Abdominal Epilepsy, Akinetic Seizures, Auto-nomic seizures, Massive Bilateral Myoclonus, Catamenial Epilepsy, Drop seizures, Emotional seizures, Focal seizures, Gelastic seizures, Jacksonian March, Lafora Disease, Motor seizures, Multifocal seizures, Neonatal seizures, Nocturnal seizures, Photosensitive seizure, Pseudo seizures, Sensory seizures, Subtle seizures, Sylvan Seizures, Withdrawal seizures, Visual Reflex Seizures amongst others. Each type presents with its own unique combination of seizure type, typical age of onset, EEG findings, treatment, and prognosis. The most widespread classification of the epilepsies divides epilepsy syndromes by location or distribution of seizures (as revealed by the appearance of the seizures and by EEG) and by cause. Syndromes are divided into localization-related epilepsies, generalized epilepsies, or epilepsies of unknown localization.
Localization-related epilepsies, sometimes termed partial or focal epilepsies, arise from an epileptic focus, a small portion of the brain that serves as the irritant driving the epileptic response. Generalized epilepsies, in contrast, arise from many independent foci (multifocal epilepsies) or from epileptic circuits that involve the whole brain. Epilepsies of unknown localization remain unclear whether they arise from a portion of the brain or from more widespread circuits.
Epilepsy syndromes are further divided by presumptive cause: idiopathic, symptomatic, and cryptogenic. Idiopathic epilepsies are generally thought to arise from genetic abnormalities that lead to alteration of basic neuronal regulation. Symptomatic epilepsies arise from the effects of an epileptic lesion, whether that lesion is focal, such as a tumor, or a defect in metabolism causing widespread injury to the brain. Cryptogenic epilepsies involve a presumptive lesion that is otherwise difficult or impossible to uncover during evaluation.
Some epileptic syndromes are difficult to fit within this classification scheme and fall in the unknown localization/etiology category. People who only have had a single seizure, or those with seizures that occur only after specific precipitants ("provoked seizures"), have "epilepsies" that fall into this category. Febrile convulsions are an example of seizures bound to a particular precipitant. Landau-Kleffner syndrome is another epilepsy which, because of its variety of EEG distributions, falls uneasily in clear categories. More confusingly, certain syndromes like West syndrome featuring seizures such as Infantile spasms can be classified as idiopathic, syndromic, or cryptogenic depending on cause and can arise from both focal or generalized epileptic lesions.
Epilepsy is usually treated with medication prescribed by a physician; primary caregivers, neurologists, and neurosurgeons all frequently care for people with epilepsy. In some cases the implantation of a stimulator of the vagus nerve, or a special diet can be helpful. Neurosurgical operations for epilepsy can be palliative, reducing the frequency or severity of seizures; or, in some patients, an operation can be curative.
Many notable people, past and present, have carried the diagnosis of epilepsy. In many cases, their epilepsy is a footnote to their accomplishments; for some, it played an integral role in their fame. Historical diagnoses of epilepsy are not always certain; there is controversy about what is considered an acceptable amount of evidence in support of such a diagnosis.