In normal brain functioning, millions of tiny electrical signals are generated by the nerve cells of the brain and other parts of the body. When a seizure occurs, it indicates that something has gone wrong with the electrical system of the brain.
A seizure is like a brief, temporary disturbance within the electrical system of the brain. Seizure activity can occur in just one region of the brain (partial seizure) or it can affect many regions (generalized seizure). Seizures are categorized as generalized or partial.
About 60 percent of people with epilepsy have one of the different types of partial seizures. In a simple partial seizure, the person remains conscious but may experience unusual feelings or sensations. In a complex partial seizure, the person may have a change or loss of consciousness. The change in consciousness may be an altered or dreamlike experience.
Generalized seizures usually cause loss of consciousness, falls or massive muscles spasms. Generalized seizures are also broken down into different types. In absence or petit mal seizures the person may appear to be staring into space. With tonic seizures the muscles of the body stiffen, generally those in the back, legs, and arms. Clonic seizures cause repeated jerking movements of muscles on both sides of the body. Tonic-clonic seizures or grand mal seizures are a mixture of symptoms, including stiffening of the body and repeated jerks of the arms and/or legs, as well as loss of consciousness.
Epilepsy is diagnosed when a person has recurrent seizures. There are more than 20 different seizure disorders. The most easily recognized is the convulsion seizure that is characterized by shaking movements of the body and a period of decreased mental awareness. Other, less apparent forms of seizures may affect a person's awareness, muscle control or sensory perception.
This article was reviewed and updated June 2007.
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