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What is a seizure disorder? – The party line in 2017

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In answering the question – what is a seizure disorder – it is proper to point out the nuances of the meaning of the term.  They are the general, scientific and practical definitions. The general meaning is one that the public embraces and understands.  It is also one that many in the healthcare community that don’t specialize in the treatment of the problem grasp. The theoretical definition is the one endorsed by the foremost scientific body that heads research into the problem.  The practical definition is the one that doctors employ to diagnose and treat the condition.  

What is a seizure disorder?

A seizure disorder is a synonym for epilepsy.  The public tends to prefer the term seizure disorder because it what is a seizure disorderis softer and does not carry the stigma attached to the term epilepsy.  The medical community, though, prefers the term epilepsy. In simple terms, a seizure disorder is a condition in which a person has recurring seizures or is at risk for such.   

The scientific definition of epilepsy is the one endorsed by The International League Against Epilepsy (ILAE) – the world’s main scientific body devoted to the study of epilepsy.  It explains: where the problem is; how it presents; its effects; and the requirements for diagnosis.

In 2005 an ILAE task force published a document officially defining epilepsy.  That definition verbatim is the following:  

what is a seizure disorder

An epileptic seizure is the short-lived occurrence of signs and/or symptoms that correlate with excessive epileptic seizureelectrical discharge by brain cells. 

The preceding definition of epilepsy is a bit much for public consumption and is not hands-on. But when translated for practical use; epilepsy is two or more unprovoked (or reflex) seizures more than 24 hours apart.  This has been the practical definition for many years until some recent changes to it under the auspices of ILAE.  Those changes broadened it; the purpose was to make it more real-world.

An unprovoked seizure is one that meets either of the following criteria.

  1. It occurs in the absence of an insult to the CNS that has the potential of triggering a seizure.
  1. It occurs following a brain insult with the potential to trigger a seizure, but outside of the estimated time interval.  In other words, it occurs too far out from the time of the insult to link the two events. 

An insult that triggers a seizure is commonly macroscopic structural injury to the brain.  But it might also be disruption of brain tissue at the molecular level or a biochemical disturbance. Unprovoked seizures are thus, ones in which the immediate cause (trigger) of the acute event is unknown.    

Reflex seizures are included in the definition because they are artificially provoked and are not the result of a reflex seizuretrue physical insult to the brain.  A reflex seizure is one provoked by flashing light shone in the eyes.  In fact, photic stimulation – shining flashing light into the eyes during an EEG – often helps diagnose a seizure disorder. 

Some of the more common brain insults that can provoke seizures are the following:

  • head trauma
  • stroke
  • a brain tumor
  • brain surgery
  • brain hypoxia
  • CNS infection  
  • sleep deprivation  
  • alcohol consumption or withdrawal
  • certain drugs
  • the active phase of multiple sclerosis or other autoimmune diseases 
  • metabolic derangements (chemical imbalances) such as hypoglycemia
  • fever in children

 A person might have a single unprovoked seizure well after a structural insult to the brain such as a stroke, tumor infection, trauma, etc., yet has a risk of experiencing a second unprovoked seizure at some point in the future which is comparable to that of a person who has had two unprovoked episodes more than 24 hours apart.  To allow for this nuance ILAE added a provision to the definition of epilepsy in 2013. It is a statement to the effect that epilepsy is one unprovoked seizure if the risk of another one occurring over the next ten years is > 60%.  The > 60% is comparable to the risk after two unprovoked seizures.

At the same time in 2013 ILAE also endorsed another change to the definition of epilepsy. The purpose of it was to recognize certain individuals as having outgrown the disease, and no longer having it. That change was the addition of epilepsy syndrome to the definition. It applies to persons with an age-dependent epilepsy syndrome who are past the usual age when it ceases to exist (if applicable), or who have been seizure-free for the last ten years and who have been off seizure medication the last five years.  

An epilepsy syndrome is a cluster of data about a person’s seizure disorder.  Its purpose is to help doctors provide better treatment of the problem; predict whether or not a person will outgrow it; and to know if it will be resistant to treatment.  Depending on the syndrome, the features comprising it might be a combination of any of the following:

  • Type of seizure(s)
  • The age of onset
  • The age of resolution (if applicable)
  • The cause
  • If it is inherited
  • The presence of certain EEG patterns during and in between seizures
  • Factors that provoke the seizures
  • The part of the brain involved
  • Seizure frequency and severity
  • Genetic information
  • Findings on brain imaging studies, such as an MRI scan or CT scan
  • The prospects of recovery
  • Other associated disorders

With the recent changes considered, the current official definition of epilepsy in its original wording is the following: 

what is a seizure disorder

ILAE along with the International Bureau for Epilepsy, made one other change to broaden the definition of epilepsy. That was the designation of it as a disease rather than a disorder.  The reason as stated was to stress the seriousness of the problem to the public.  After all, sudden unexpected death is the leading cause of epilepsy-related death in young adults in whom the disease is uncontrolled.

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Seizure Types by Name in the ILAE 2017 Classification System

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