Table 10.1

Clinical and EEG manifestations of typical absence seizures21

Typical absence seizures: clinical manifestations
The hallmark of the absence attack is a sudden onset, interruption of ongoing activities, a blank stare, possibly a brief upward rotation of the eyes. If the patient is speaking, speech is slowed or interrupted, if walking, he stands transfixed; if eating, the food will stop on his way to the mouth. Usually the patient will be unresponsive when spoken to. In some, attacks are aborted when the patient is spoken to. The attack lasts from a few seconds to half a minute and evaporates as rapidly as it commenced.
Clinical seizure type
  • Absence with impairment of consciousness only. The above description fits the description of absence simple in which no other activities take place during the attack.
  • Absence with mild clonic components. Here the onset of the attack is indistinguishable from the above, but clonic components may occur in the eyelids, at the corner of the mouth, or in other muscle groups, which may vary in severity from almost imperceptible movements to generalised myoclonic jerks. Objects held in the hand may be dropped.
  • Absence with atonic components. Here there may be a diminution in tone of muscles subserving posture as well as in the limbs leading to drooping of the head, occasionally slumping of the trunk, dropping of the arms, and relaxation of the grip. Rarely tone is sufficiently diminished to cause this person to fall.
  • Absence with tonic components. Here during the attack tonic muscular contraction may occur, leading to increase in muscle tone, which may affect the extensor muscles or the flexor muscles symmetrically or asymmetrically. If the patient is standing the head may be drawn backward and the trunk may arch. This may lead to retropulsion. The head may tonically draw to one or another side.
  • Absence with automatisms. Purposeful or quasipurposeful movements occurring in the absence of awareness during an absence attack are frequent and may range from lip licking and swallowing to clothes fumbling or aimless walking. If spoken to, the patient may grunt or to the spoken voice and when touched or tickled may rub the site. Automatisms are quite elaborate and may consist of combinations of the above described movements or may be so simple as to be missed by causal observation.
  • Absence with autonomic components. These may be pallor and less frequently flushing, sweating, dilatation of pupils and incontinence of urine.
Mixed forms of absence frequently occur.
Absence EEG manifestations
Ictal EEG
  • Usually regular and symmetrical 3Hz but may be 2–4 Hz spike-and-slow wave complexes and may have multiple spike-and-slow wave complexes.
    Abnormalities are bilateral.
EEG interictal expression
  • Background activity usually normal although paroxysmal activity (such as spikes or spike-and-slow wave complexes) may occur. This activity is usually regular and symmetrical.

From the Commission on Classification and Terminology of the ILAE21 with the permission of the Commission and the editor of Epilesia

From: Chapter 10, Idiopathic Generalised Epilepsies

Cover of The Epilepsies
The Epilepsies: Seizures, Syndromes and Management.
Panayiotopoulos CP.
Oxfordshire (UK): Bladon Medical Publishing; 2005.
Copyright © 2005, Bladon Medical Publishing, an imprint of Springer Science+Business Media.

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