Epilepsy Seizure Types and Symptoms
Based on the type of behavior and brain activity, seizures are divided into two broad categories: generalized and partial (also called local or focal). Classifying the type of seizure helps doctors diagnose whether or not a patient has epilepsy.
Generalized seizures are produced by electrical impulses from throughout the entire brain; partial seizures are produced (at least initially) by electrical impulses in a relatively small part of the brain. The part of the brain generating the seizures is sometimes called the focus. The most common types of seizures are listed below:
(Produced by the entire brain)
|1. "Grand Mal" or Generalized tonic-clonic||Unconsciousness, convulsions, muscle rigidity|
|2. Absence||Brief loss of consciousness|
|3. Myoclonic||Sporadic (isolated), jerking movements|
|4. Clonic||Repetitive, jerking movements|
|5. Tonic||Muscle stiffness, rigidity|
|6. Atonic||Loss of muscle tone|
There are six types of generalized seizures. The most common and dramatic, and therefore the most well known, is the generalized convulsion, also called the grand-mal seizure. In this type of seizure, the patient loses consciousness and usually collapses. The loss of consciousness is followed by generalized body stiffening (called the "tonic" phase of the seizure) for 30 to 60 seconds, then by violent jerking (the "clonic" phase) for 30 to 60 seconds, after which the patient goes into a deep sleep (the "postictal" or after-seizure phase). During grand-mal seizures, injuries and accidents may occur, such as tongue biting and urinary incontinence.
Absence seizures cause a short loss of consciousness (just a few seconds) with few or no symptoms. The patient, most often a child, typically interrupts an activity and stares blankly. These seizures begin and end abruptly and may occur several times a day. Patients are usually not aware that they are having a seizure, except that they may be aware of "losing time."
Myoclonic seizures consist of sporadic jerks, usually on both sides of the body. Patients sometimes describe the jerks as brief electrical shocks. When violent, these seizures may result in dropping or involuntarily throwing objects.
Clonic seizures are repetitive, rhythmic jerks that involve both sides of the body at the same time.
Tonic seizures are characterized by stiffening of the muscles.
Atonic seizures consist of a sudden and general loss of muscle tone, particularly in the arms and legs, which often results in a fall.