Seizure Disorders

Classification of Seizures and Epilepsy

A seizure is a set of clinical symptoms due to abnormal electrical activity of the brain. Epilepsy is a syndrome where there have been recurrent unprovoked seizures or a single unprovoked seizure with findings to indicate that there is a comparable risk of subsequent seizure as would be seen in a patient with two unprovoked seizures. Therefore, all patients with epilepsy have seizures, whereas not all patients with seizures have epilepsy.

Seizures come in a variety of types with different clinical features. The classification scheme has evolved, and some authors and practitioners adhere to now-obsolete schemes. Because of this, neurologists need to be aware of the new accepted schemes and the parallels in prior terminology.

Seizures are first classified into generalized or focal onset. Generalized seizures are those that have a generalized onset, that is, the seizures did not start in a specific focus and then spread. These are subdivided into motor onset and nonmotor onset. Motor onset seizures would include the generalized tonic-clonic (GTC) seizures. Nonmotor onset seizures would include absence seizures.

Classification of epilepsies is complex, but for the purposes of localization and diagnosis it is appropriate to introduce it here. The seizure classification is first and most important.

Epilepsies are classified as focal, generalized, combination of focal and generalized, and unknown. This classification is based on the origin of the discharges that comprise the seizures. There are also classification strata based on whether the seizures are structural, genetic, metabolic, infectious, immune, or unknown, which are not pivotal for localization.

Classification of seizures is as follows:

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  Focal onset

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    Awareness

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      Aware

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      Impaired awareness

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    Onset

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      Motor onset

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      Nonmotor onset

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    Focal to bilateral tonic-clonic seizures

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  Generalized

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    Motor onset

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    Nonmotor onset (absence)

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  Unknown onset

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    Motor onset

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      Tonic-clonic

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      Epileptic spasms

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    Nonmotor onset

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    Unclassified

Classification of epilepsies is as follows:

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  Epilepsy types

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    Focal

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    Generalized

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    Combination of focal and generalized

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    Unknown

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  Etiologies

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    Structural

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    Genetic

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    Infectious

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    Metabolic

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    Immune

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    Unknown

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  Epilepsy syndromes

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    Idiopathic generalized epilepsies

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      Childhood absence

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      Juvenile absence

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      Juvenile myoclonic

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      Generalized tonic-clonic

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    Self-limited focal epilepsies

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      With centrotemporal spikes

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      Self-limited occipital epilepsies

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      Other self-limited frontal, temporal, or parietal epilepsies

Clinical Features of Seizure Types