Doctors have described more than 30 different types of seizures.
Seizures are divided into two major categories — focal seizures and generalized seizures. However, there are many different types of seizures in each of these categories.
Focal seizures, also called partial seizures, occur in just one part of the brain. About 60 percent of people with epilepsy have focal seizures. These are frequently described by the area of the brain in which they originate — for example, someone might be diagnosed with focal frontal lobe seizures.
In a simple focal seizure, the person will remain conscious but experience unusual feelings or sensations that can take many forms. The person may experience sudden and unexplainable feelings of joy, anger, sadness, or nausea. He or she also may hear, smell, taste, see, or feel things that are not real.
In a complex focal seizure, the person has a change in or loss of consciousness. His or her consciousness may be altered, producing a dreamlike experience. People having a complex focal seizure may display strange, repetitious behaviors such as blinks, twitches, mouth movements, or even walking in a circle. These repetitious movements are called automatisms.
More complicated actions, which may seem purposeful, can also occur involuntarily. Patients may also continue activities they started before the seizure began, such as washing dishes in a repetitive, unproductive fashion. These seizures usually last just a few seconds.
Some people with focal seizures, especially complex ones, may experience auras — unusual sensations that warn of an impending seizure. These auras are actually simple focal seizures in which the person maintains consciousness. The symptoms an individual person has, and the progression of those symptoms, tend to be stereotyped, or similar every time.
The symptoms of focal seizures can easily be confused with other disorders. For instance, the dreamlike perceptions associated with a complex focal seizure may be misdiagnosed as migraine headaches, which also may cause a dreamlike state. The strange behavior and sensations caused can also be mistaken for symptoms of narcolepsy, fainting, or even mental illness. It may take many tests and careful monitoring by an experienced physician to tell the difference between epilepsy and other disorders.
Generalized seizures are a result of abnormal neuronal activity on both sides of the brain, and may cause loss of consciousness, falls, or massive muscle spasms.
There are many kinds of generalized seizures:
In absence seizures, the person may appear to be staring into space and/or have jerking or twitching muscles. These seizures are sometimes referred to as petit mal seizures, which is an older term.
Tonic seizures cause stiffening of muscles of the body, generally those in the back, legs, and arms.
Clonic seizures cause repeated jerking movements of muscles on both sides of the body.
Myoclonic seizures cause jerks or twitches of the upper body, arms, or legs.
Atonic seizures cause a loss of normal muscle tone. The affected person will fall down or may drop his or her head involuntarily.
Tonic-clonic seizures cause a mixture of symptoms, including stiffening of the body and repeated jerks of the arms and/or legs as well as loss of consciousness. Tonic-clonic seizures are sometimes referred to by an older term: grand mal seizures.
Not all seizures can be easily defined as either focal or generalized. Some people have seizures that begin as focal seizures, but then spread to the entire brain. Other people may have both types of seizures but with no clear pattern.
Society’s lack of understanding about the many different types of seizures is one of the biggest problems for people with epilepsy. People who witness a non-convulsive seizure often find it difficult to understand that behavior which looks deliberate is not under the person’s control. In some cases, this has led to the affected person being arrested or admitted to a psychiatric hospital. To combat these problems, people everywhere need to understand the many different types of seizures and how they may appear.