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Definition: seizure from The Macquarie Dictionary
1.

the act of seizing.

Plural: seizures

2.

a taking possession, legally or by force.

Plural: seizures

3.

Pathology a convulsion.

Plural: seizures


Summary Article: SEIZURES
from Epilepsy A to Z: A Concise Encyclopedia

A seizure is an electrographic or behavioral change resulting from a sudden excessive, hypersynchronous discharge of cerebral neurons. A seizure is a symptom and not a disease. The behavioral changes of a seizure are stereotyped associated with variable impairment of consciousness, in addition to sensory, motor, cognitive, or autonomic changes. Epileptic seizures are a more common neurologic problem than Parkinson's disease or multiple sclerosis 1. The importance of understanding seizures in PWE stems from their common occurrence and lack of understanding about those affected by the condition. The two major categories of seizures are localization-related and generalized seizures. Seizures that originate from focal brain regions are associated with localizationrelated epilepsy, and generalized seizures are associated with generalized epilepsy and characterized by diffuse, bilateral cerebral involvement at onset 2. The types of seizures are listed in Table 1, though the semiologic spectrum of “focal” and generalized seizures is often appreciated with clinical overlap.

Table 1 Seizure Types

Seizures depicted in bold may be associated with IGE or SGE; those in italics are associated with SGE.

Localization-related (partial-onset, focal)

Generalized

Simple partial, complex partial, and secondarily generalized

Convulsive

Generalized tonic-clonic, tonic, myoclonic

Nonconvulsive atonic, absence (typical and atypical)

The diagnosis of the appropriate seizure type is crucial so that iatrogenic exacerbation of generalized seizures or incomplete treatment of partial seizures does not occur. Classification systems attempt to categorize seizures for the purpose of defining the epilepsy syndrome (e.g., myoclonic and generalized tonicclonic seizures of juvenile myoclonic epilepsy syndrome). EEG has been used as an extension of the semiology as an integral part of the classification system. However, separate classification systems based upon semiology alone have also been employed successfully in the clinical management of patients of various age ranges 3. A proposal to adopt a five-axis classification system (see Classification) as well as revised terminology 4 has been put forth. Seizures that reflect an idiopathic (or “primary”) origin are associated with a genetic predisposition and by definition have no structural basis. In adulthood, generalized (clonic) tonic-clonic, absence (typical), and myoclonic seizures are best represented by IGE. Seizures associated with diffuse structural brain injury reflect a SGE that is typically manifested by multiple mixed seizure types, including tonic/atonic (“drop attacks”) and atypical absence seizures (absences with <3 Hz spike-and-waves on EEG). Those with symptomatic causes bear a known structural cause, while those with a cryptogenic origin have a suspected symptomatic but unidentified cause. Partial seizures may be idiopathic (e.g., benign partial epilepsies of childhood). Some generalized seizures may manifest “focal” or lateralized features 2. Some partial-onset seizures may appear with bilateral motor involvement from rapid secondary generalization. The key features of the seizure types are listed in Table 2.

Table 2 Seizure Types and Key Features of Clinical Expression

Seizure type

Key features

Simple partial (SPS)

Consciousness is unimpaired (“aura”)

Complex partial (CPS)

Consciousness is impaired/nonconvulsive

Secondarily generalized

Convulsion that may begin first as a SPS or CPS

Generalized tonic-clonic

Convulsion of nonfocal origin (“grand mal”)

Myoclonic

Single lightning-like jerks, often in clusters

Typical absence

Very brief staring episodes usually in children (“petit mal”)

Tonic/atonic

Abrupt generalized rigidity/loss of tone (“drop attacks”)

Atypical absence

Staring; longer and more “complex” than typical absence

1

  • Theodore W H; Spencer S S; Wiebe S et al. ILAE Report. Epilepsy in North America: a report prepared under the auspices of the global campaign against epilepsy, the interntional bureau for epilepsy, the international league against epilepsy, and the world health organization. Epilepsia. (2006); vol. 47 (iss. 10): p. 1700-1722.
2

  • Holmes M D; Brown M; Tucker, D M. Are “generalized” seizures truly generalized? Evidence of localized mesial frontal and frontopolar discharges in absence. Epilepsia. (2004); vol. 45 (iss. 12): p. 1568-1579.
3

  • Luders H; Acharya J; Baumgartner C et al. A new epileptic seizure classification based exclusively on ictal semiolgy. Acta Neurol Scand. (1999); vol. 99 (iss. 3): p. 137-141.
4

  • Fisher R; Boas W; Blume W et al. Epileptic seizures and epilepsy: definitions proposed by the International League Against Epilepsy (ILAE) and the International Bureau for Epilepsy (IE). Epilepsia. (2005); vol. 46 : p. 470-472.
Copyright © 2009 Springer Publishing Company

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