Epilepsy Seizure Types

A seizure is the result of abnormal activity of the neurons in the brain. Neurons are cells in the brain that communicate information by sending electrochemical impulses. A seizure occurs when neurons fire off abnormal signals, usually sent simultaneously and much more rapidly than normal. Unsure of what to do with these jumbled signals, the body responds with a seizure.

During a seizure, an individual may experience involuntary muscle contractions or lose consciousness altogether. Epilepsy seizures usually last no longer than a few minutes.

Seizure Types

Epilepsy is a complicated brain disorder, and the seizures it produces are accordingly complex. There are many different kinds of seizures. Types of seizures are categorized based on where they occur in the brain, and how much of the brain is affected during the seizure. All epilepsy seizures fall into one of two basic categories:

  • Partial (focal) onset seizures
  • Generalized seizures.

Partial Seizures

Partial (focal) onset seizures are the result of abnormal neurological activity in just one hemisphere or lobe of the brain. This category can be further subdivided into seizures that occur without loss of consciousness and those with loss of consciousness, or “simple” and “complex” partial seizures:

  • During complex partial seizures, the individual loses consciousness temporarily. She may wander around or stare blankly at nothing in particular, or carry out repetitive actions such as picking at clothing, lip smacking or hand rubbing.
  • During simple partial seizures, the individual does not lose consciousness. He may experience unusual sensory phenomena (strange sights, smells, tastes, sounds and feelings) depending on which part of the brain is affected. He may also experience involuntary jerking of the limbs.

Partial seizures can lead to generalized seizures. In this case, the partial seizure is known as a “secondarily generalized seizure” or a “bilateral convulsive seizure.”

Generalized Seizures

Generalized seizures affect both hemispheres of the brain. All generalized seizures result in a loss of consciousness. There are four main seizure types that fall under this category:

  • Absence seizures (also called “petit mal seizures”) are brief lapses of consciousness, sometimes accompanied by staring. Each lapse may only be a few seconds long.
  • Atonic seizures (also called “drop attacks”) result in a sudden loss of muscle tone. The resulting collapse may cause the individual to sustain injuries.
  • Myoclonic seizures occur as quick, short muscle contractions.
  • Tonic-clonic seizures (also called “grand mal seizures”) result in a loss of consciousness and a stiffening of the body, followed by involuntary jerking of the limbs and face. This is the most common type of seizure.

A patient does not necessarily experience only one type of seizure. Seizures may change over time, depending on factors associated with the maturing of the brain. A patient may also experience a combination of different seizure types. This can make it very difficult to diagnose types of epilepsy seizures. A consultation from a neurologist or epileptologist may aid in diagnosis and treatment.

Resources

Berg, A. T. et al. (2009). Revised terminology and concepts for organization of the epilepsies: Report of the Commission on Classification and Terminology. Retrieved March 10, 2010, from http://www.ilae-epilepsy.org/Visitors/Centre/ctf/ctfoverview.cfm

Dekker, P.A. (2002). Epilepsy: A manual for medical and clinical officers in Africa. Retrieved March 10, 2010, from http://www.who.int/mental_health/media/en/639.pdf

Mayo Foundation for Medical Education and Research Staff. (2009). Epilepsy symptoms. Retrieved March 10, 2010, from http://www.mayoclinic.com/health/epilepsy/DS00342/DSECTION=symptoms

The Epilepsy Foundation of America®Staff. (n.d.) Types of seizures. Retrieved March 10, 2010 from http://www.epilepsyfoundation.org/about/types/types/index.cfm