Introduction
Epilepsy is characterized by unprovoked, recurring seizures that disrupt the nervous system and can cause mental and physical dysfunction. In the US, about two and a half million people are affected by epilespy and seizures. About 10% of the American population will experience at least one seizure during their lifetime.
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| The structures of the brain include: the brainstem, consisting of the spinal cord, the medulla oblongata, the pons and the midbrain; the cerebellum; the cerebrum (one half, or hemisphere shown), and the diencephalon . |
Epilepsy affects all age groups. Males have a slightly higher risk than females. The incidence is highest in children with another, but lesser, peak occurring after age 60. According to one estimate, 14% of epilepsy patients are under 15 years old and approximately a quarter are over age 64.
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Every year between 25,000 and 40,000 American children have a first seizure that is unrelated to a fever. Epilepsy is decreasing in childhood but increasing in the elderly, probably because of mild strokes and cardiac arrest.
Criteria for Classifying Epilepsies and Seizures
Epilepsy is not a single disorder but rather a wide spectrum of problems. What all types of epilepsy share are recurrent, unprovoked seizures caused by an uncontrolled electrical discharge from nerve cells in the cerebral cortex. This part of the brain controls higher mental functions, general movement, and the functions of the internal organs in the abdominal cavity, perception, and behavioral reactions.
Seizures are a symptom of epilepsy. At this time, epilepsy types are generally into two categories, which are based on the specific biologic mechanisms involved in the seizure and the anatomical location of the seizure. They two types are:
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Partial (also called focal or localized) seizures. These seizures are more common than generalized seizures and occur in one or more specific locations in the brain. In some cases, partial seizures can spread to wide regions of the brain. They are likely to develop from specific injuries, but in most cases the exact origins are unknown.
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Generalized seizures. These seizures typically occur in both sides of the brain. Many forms of these seizures are genetically based. There is usually normal neurologic function.
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