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Epilepsy is generally classified into two main categories based on seizure type:
- 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 (idiopathic).
- 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 between episodes.
Partial Seizures (also called Focal Seizures)
These seizures are subcategorized as "simple" or "complex partial."
- Simple Partial Seizures. A person with a simple partial seizure (sometimes known as Jacksonian epilepsy) does not lose consciousness, but may experience confusion, jerking movements, tingling, or odd mental and emotional events. Such events may include deja vu, mild hallucinations, or extreme responses to smell and taste. After the seizure, the patient usually has temporary weakness in certain muscles. These seizures typically last about 90 seconds.
- Complex Partial Seizures. Slightly over half of seizures in adults are complex partial type. About 80% of these seizures originate in the temporal lobe, the part of the brain located close to the ear. Disturbances there can result in loss of judgment, involuntary or uncontrolled behavior, or even loss of consciousness. Patients may lose consciousness briefly and appear to others as motionless with a vacant stare. Emotions can be exaggerated; some patients even appear to be drunk. After a few seconds, a patient may begin to perform repetitive movements, such as chewing or smacking of lips. Episodes usually last no more than 2 minutes. They may occur infrequently, or as often as every day. A throbbing headache may follow a complex partial seizure.
In some cases, simple or complex partial seizures evolve into what are known as secondarily generalized seizures. The progress may be so rapid that the partial stage is not even noticed.
Generalized Seizures
Generalized seizures are caused by nerve cell disturbances that occur in more widespread areas of the brain than do partial seizures. Therefore, they have a more serious effect on the patient. They are further subcategorized as tonic-clonic (or grand mal), absence (petit mal), myoclonic, or atonic seizures.
Tonic-Clonic (Grand Mal) Seizures. The first stage of a grand mal seizure is called the tonic phase, in which the muscles suddenly contract, causing the patient to fall and lie stiffly for about 10 - 30 seconds. Some people experience a premonition or aura before a grand mal seizure. Most, however, lose consciousness without warning. If the throat or larynx is affected, there may be a high-pitched musical sound (stridor) when the patient inhales. Spasms occur for about 30 seconds to 1 minute. Then the seizure enters the second phase, called the clonic phase. The muscles begin to alternate between relaxation and rigidity. After this phase, the patient may lose bowel or urinary control. The seizure usually lasts a total of 2 - 3 minutes, after which the patient remains unconscious for a while and then awakens to confusion and extreme fatigue. A severe throbbing headache similar to migraine may also follow the tonic-clonic phases.
Absence (Petit Mal) Seizures. Absence or petit mal seizures are brief losses of consciousness that occur for 3 - 30 seconds. Physical activity and loss of attention may pause for only a moment. Such seizures may pass unnoticed by others. Young children may simply appear to be staring or walking distractedly. Petit mal may be confused with simple or complex partial seizures, or even with attention deficit disorder. [For more information, see In-Depth Report #30: Attention deficit hyperactivity disorder.] In petit mal, however, a person may experience attacks as often as 50 - 100 times a day.
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Review Date: 01/28/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine,
Harvard Medical School; Physician, Massachusetts General Hospital.
Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M.,
Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
