Classification of Epileptic seizures

Epileptic seizures and epilepsies are classified separately.

Classifi cation systems are evolving under the auspices of the

International League against Epilepsy.

Epileptic seizures

The fi rst division is into generalized or focal.

Generalized epileptic seizures

A generalized epileptic seizure is one in which abnormal activity

occurs in both cerebral hemispheres from the onset of the seizure.

Different subtypes include:

Tonic-clonic seizures (GTCS): involuntary muscle contractions

occur which may be sustained (tonic) or interrupted (clonic).

Synonyms include ‘convulsion’ and ‘grand-mal seizure’ (a term

best avoided). Tonic or clonic seizures may occur, as well as

tonic-clonic.

Absence seizures: a brief, 10–30 s loss of consciousness with

staring and unresponsiveness but no loss of posture.

Myoclonic seizures: brief, muscular contractions that occur

singly or are repeated a few times. Consciousness is not

altered.

Astatic (atonic) seizures,‘drop attacks’: a sudden brief reduction

in muscle tone causing loss of posture.

Focal epileptic seizures

A focal seizure is one in which abnormal activity is initially confi

ned to one part of the brain. ‘Partial’, ‘local’, or ‘localized’ are

synonyms. Classifi cation is into simple, in which consciousness is

preserved, and complex, in which consciousness is impaired:

Simple focal seizures:

with motor activity: ‘Jacksonian’ seizures

with sensory symptoms: somatosensory, numbness

with autonomic features: pupillary or skin colour changes

with psychic symptoms: feelings of fear, rage, déjà vu. There

may be visual, auditory or olfactory hallucinations.

Complex focal seizures:

impaired consciousness: may occur alone and may be

present from onset or supervene in an initially simple focal

seizure

automatisms: semi-purposeful activities during which the

patient is vague and unresponsive, may occur.

Seizures occur which do not fi t neatly into the above categories.

It may be diffi cult to determine whether a seizure type is truly

focal or generalized. Examples include:

Focal seizures with rapid secondary generalization

Infantile spasms: widespread muscular contractions.

Epilepsies and epilepsy syndromes

Epilepsies are classifi ed by the type of epileptic seizure occurring

into generalized epilepsies and focal epilepsies. A further

subdivision is made according to aetiology into:

Idiopathic (primary): no identifi able cause apart from genetic

Symptomatic: in which the cause is identifi able or presumed.

Epilepsy syndromes are also defi ned by age of onset, EEG

fi ndings, and additional clinical or pathological features.

The classification continues to evolve in the light of new

research, but a simplifi ed version is as follows:

Generalized epilepsies and syndromes

Idiopathic generalized epilepsy (IGE):

juvenile myoclonic epilepsy (JME)

childhood absence epilepsy (CAE)

juvenile absence epilepsy (JAE)

generalized epilepsy with febrile seizures+ (GEFS+)

benign familial neonatal seizures (BFNS)

benign familial infantile seizures (BFIS)

benign myoclonic epilepsy of infancy

epilepsy with GTCS on awakening

Symptomatic generalized epilepsy:

cerebral malformations

inborn errors of metabolism.

Focal epilepsies and syndromes

Idiopathic focal epilepsy:

benign childhood epilepsy with centrotemporal spikes

autosomal dominant nocturnal frontal lobe epilepsy

Symptomatic focal epilepsy:

temporal lobe epilepsy with hippocampal sclerosis

Rasmussen’s encephalitis

hemiconvulsion–hemiplegia syndrome.

In addition to the above, there are three further categories

which do not fi t easily into the above classifi cation:

Refl ex epilepsies:

idiopathic photosensitive occipital lobe epilepsy

Epileptic encephalopathies:

myoclonic-astatic epilepsy

West syndrome

Dravet syndrome: severe myoclonic epilepsy of infancy

Lennox–Gastaut syndrome

Progressive myoclonic epilepsies:

Unverricht–Lundborg disease or Baltic myoclonus

neuronal ceroid lipofuscinosis

myoclonic epilepsy with ragged red fi bres (MERRF).

Febrile seizures occurring alone are not classifi ed as epilepsy

but also occur, together with afebrile seizures in several epilepsy

syndromes such as childhood absence epilepsy and generalized

epilepsy with febrile seizures plus (GEFS+).