What Are the Different Kinds 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 Onset Seizures

Focal seizures occur when just one part of the brain has abnormal electrical activity. About 60 percent of people with epilepsy have focal seizures. These seizures are usually given a name based on the area of the brain in which they take place. For example, someone might be diagnosed with focal frontal lobe seizures.

Focal seizures are further separated into 2 categories:

  • In “simple” focal seizures, the individual remains conscious but experiences unusual feelings or sensations. The person may have 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 loss of consciousness. He or she may report having a dreamlike experience. People having a complex focal seizure may also have strange, repeating behaviors such as blinks, twitches, mouth movements or even walking in circles. These movements are called automatisms.

Sometimes, during a focal seizure, a person will perform more complicated actions, without meaning to do them. Patients may also continue to do the 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 focal seizures, may experience auras – unusual sensations that warn of an impending seizure. These auras are actually simple focal seizures in which the person stays conscious. How these symptoms appear and how they progress tend to be stereotyped, which means they are similar every time.

The symptoms of focal seizures can easily be confused with other disorders. For instance, the dreamlike quality of a complex focal seizure may be wrongly diagnosed as migraine headaches, which also may cause a dreamlike state. The strange behavior and sensations caused by focal seizures also can be mistaken for symptoms of narcolepsy (a sleep disorder), fainting or even mental illness. It may take evaluation by an experienced physician to tell the difference between epilepsy and other disorders.

Some focal seizures secondarily generalize. This means that the seizure in one place of the brain but as the seizure proceeds, it ultimately involves both sides of the brain resulting in a generalized seizure.

Generalized Seizures

Generalized seizures are caused by abnormal nerve cell activity that starts on both sides of the brain. These seizures may cause loss of consciousness. Some generalized seizures are “convulsive” meaning they have generalized motor movements. Other generalized seizures are “non-convulsive” meaning that the seizure occurs without generalized motor movements.

Types of generalized seizures:

  • Absence seizures are “non-convulsive” 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.
  • 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.
  • Seizures are sometimes referred to by an older term, grand mal seizures.
  • 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.

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Resources:

Epilepsy Foundation
Diagnosing Epilepsy