Different Types of Seizures
According to the Merck Index, a seizure is a periodic disturbance in the brain's electrical activity that results in some degree of temporary brain dysfunction. There are several different types of seizures with the distinguishing factors being the point of origin and the severity of the symptoms.
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Major Categories
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All seizures fall into one of two major categories: primary generalized seizures and secondary generalized seizures. Primary generalized seizures are widespread throughout the brain. Secondary generalized seizures, or partial seizures, start in an isolated area of the brain and can either remain isolated or eventually spread throughout the brain.
Tonic, Clonic and Tonic-Clonic Seizures
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A tonic-clonic, or grand mal seizure, is a type of primary generalized seizure characterized mostly by unconsciousness, muscle stiffness and convulsions. Because of the nature of the convulsions combined with loss of consciousness, there is a significant chance for injury.
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Absence Seizure
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The primary characterization of an absence seizure is a brief loss of consciousness that typically lasts only a few seconds. Although categorized as a primary generalized seizure, the individual experiencing the seizure typically does not even realize it is occurring and only experiences a sensation of lost time.
Myoclonic, Clonic and Tonic Seizures
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Other types of primary generalized seizures include myoclonic, clonic and tonic seizures. Myoclonic seizures consist of sporadic jerking movements. Less severe are clonic seizures, in which there is repetitive muscle contractions, and tonic seizures, in which there is simply muscle stiffening.
Simple Seizures
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One classification of partial seizures, or secondary generalized seizures, is the simple class, which consists of simple, simple motor, simple sensory and simple psychological. During simple seizures, awareness is retained but the outward symptoms can range from muscle rigidity to unusual sensory experiences to emotional disturbances depending upon the type.
Complex Seizure
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A complex seizure is a type of partial seizure that is characterized by the repeated and involuntary occurrence of specific movements, or automatisms, such as fidgeting, lip smacking or chewing. These events occur most frequently in people with head injuries.
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