Index of Seizure Types
While there are over 40 types of seizures; the following are the most common (or so we have been told):
There have been many attempts to categorize seizures, based on both the causes of seizures as well as the different seizure subtypes. A well-recognized classification system is the International Classification of Epileptic Seizure. This divides seizure types by the location in the brain that they originate from.
The two main categories of seizures include partial seizures
and generalized seizures
are those that begin in a focal or discreet area of the brain. This type can be further subdivided into:
- Simple partial: No change in consciousness occurs. Patients may experience weakness, numbness, and unusual smells or tastes. Twitching of the muscles or limbs, turning the head to the side, paralysis, visual changes, or vertigo may occur. When motor symptoms spread slowly from one part of the body to another, this "epileptic march" has been termed jacksonian epilepsy (first described by Hughlings Jackson).
- Complex partial seizures(temporal lobe): Consciousness is altered during the event. Patients may have some symptoms similar to those in simple partial seizures but have some change in their ability to interact with the environment. Patients may exhibit automatisms (automatic repetitive behavior) such as walking in a circle, sitting and standing, or smacking their lips together. Often accompanying these symptoms are the presence of unusual thoughts, such as the feeling of deja vu (having been someplace before), uncontrollable laughing, fear, visual hallucinations, and experiencing unusual unpleasant odors. These interesting symptoms are thought to be caused by abnormal discharges in the temporal lobe.
involve larger areas of the brain, often both hemispheres (sides), from the onset. They are further divided into many subtypes. The more common include:
- Tonic-clonic (grand mal): This subtype is what most people associate with seizures. Specific movements of the arms and legs and/or the face may occur with loss of consciousness. A yell or cry often precedes the loss of consciousness. Prior to this, patients may have an aura (an unusual feeling that often warns the patient that they are about to have a seizure). The person will abruptly fall and begin to have jerking movements of their body and head. Drooling, biting of the tongue, and incontinence of urine may occur. When the jerking movements stop, the patient may remain unconscious for a period of time. The seizure usually lasts 5 to 20 minutes. They often awaken confused and may sleep for a period of time. The patients may experience prolonged weakness after the event; this is termed Todds paralysis.
- Absence (petit mal): Loss of consciousness only occurs, without associated motor symptoms. Usually there is no aura, or warning. The loss of consciousness is brief; the patient may appear to be involved with the environment and briefly stop what they are doing, stare for 5 to 10 seconds, and then continue their activity. No memory of the event exits. Subtle motor movements may accompany the alteration in consciousness.
- Myoclonic: Myoclonic seizures are characterized by a brief jerking movement that arises from the central nervous system, usually involving both sides of the body. The movement may be very subtle or very dramatic. There are many different syndromes associated with myoclonic seizures, including juvenile myoclonic epilepsy, West syndrome and Lennox-Gastaut syndrome. Most cases of myoclonic epilepsy occur during the first 5 years of life.
West syndrome involves a group of symptoms including infantile spasms, retardation of psychomotor development, and a particular abnormality on the electroencephalogram (EEG) known as hypsarrhythmia. Infantile spasms are characterized by a particular posturing of the infant’s body, in which the child assumes a jack-knife, or folded, position. These spasms may occur frequently in the course of the day or may be continuous. Neurological problems are ultimately found in most of these children. The hypsarrhythmia pattern seen on the EEG is a grossly disorganized pattern of electrical brain activity. It is often difficult to control the seizures in this syndrome because they usually respond poorly to most anticonvulsant medications.
Lennox- Gastaut Syndrome
Lennox-Gastaut syndrome is characterized by the early onset of a common seizure type called minor motor seizures. These seizures include the aforementioned myoclonic seizures, atypical absence seizures, and atonic seizures. Atypical absence seizures may involve staring and brief episodes of unconsciousness. They may occur in cycles and are associated with EEG findings different from those seen in typical absence seizures. Atonic seizures may be associated with sudden loss of muscle tone.
Status epilepticus is prolonged, repetitive seizure activity that lasts more than 20 to 30 minutes, during time which the patient is unconscious. Status epilepticus is a medical emergency with a significantly poor outcome; it can result in death if not treated aggressively. Its causes include improper use of certain medications, stroke, infection, trauma, cardiac arrest, drug overdose, and brain tumor.