Which physical findings are characteristic of absence seizures?

Updated: Sep 25, 2018
  • Author: Scott Segan, MD; Chief Editor: Selim R Benbadis, MD  more...
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Physical and neurologic findings are normal in children with idiopathic generalized epilepsies. Having the child hyperventilate for 3-5 minutes can often provoke absence seizures. This procedure can easily be performed in the clinic or office, and the result is diagnostic.

On clinical examination, typical absence seizures appear as brief staring spells. Patients have no warning or postictal phase, and if engaged in gross motor activity, such as walking, they may stop and stand motionless or they may continue to walk. Children are not responsive during the seizure and have no memory of what happened during the attack; they are generally unaware that a seizure has occurred. (See Table 1, below.)

Atypical absence seizures, which occur in patients with symptomatic generalized epilepsies, are usually longer than typical absences and often have more gradual onset and resolution.

In symptomatic generalized epilepsies, physical and neurologic findings may be abnormal, reflecting the underlying disorder. Physical examination may reveal stigmata of a genetic disease, such as a neurocutaneous disorder (eg, tuberous sclerosis) or an inborn error of metabolism. Neurologic examination may show signs of developmental delay or more specific signs, such as spastic paresis in cerebral palsy.

Table 1. Clinical and EEG Findings in Typical and Atypical Absence Seizures* (Open Table in a new window)

Type of Clinical Seizure

EEG Findings

Typical absence

Impairment of consciousness only

Usually regular and symmetrical 3 Hz, possible 2- to 4-Hz spike-and-slow-wave complexes, and possible multiple spike-and-slow-wave complexes

Mild clonic components

Atonic components

Tonic component


Autonomic components

Atypical absence

Changes in tone more pronounced than those of typical absence seizure

EEG more heterogeneous than in typical absence; may include irregular spike-and-slow-wave complexes, fast activity, or other paroxysmal activity; abnormalities bilateral but often irregular and asymmetrical

Nonabrupt onset or cessation abrupt

*May be seen alone or in combination.

Adapted from Dreifuss FE. Classification of epileptic seizures. In: Engel J Jr, Pedley TA, eds. Epilepsy: A Comprehensive Textbook. Philadelphia, PA: Lippincott-Raven;1997.

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