What are absence seizures?

Updated: Sep 25, 2018
  • Author: Scott Segan, MD; Chief Editor: Selim R Benbadis, MD  more...
  • Print
Answer

Answer

Absence seizures are a type of generalized non-motor seizures. [1] They were first described by Poupart in 1705, and later by Tissot in 1770, who used the term petit access. In 1824, Calmeil used the term absence. [2] In 1935, Gibbs, Davis, and Lennox described the association of impaired consciousness and 3-Hz spike-and-slow-wave complexes on electroencephalograms (EEGs). [3]

Absence seizures occur in idiopathic and symptomatic generalized epilepsies. [4] Among the idiopathic generalized epilepsies, absence seizures are seen in childhood absence epilepsy (pyknolepsy), juvenile absence epilepsy, and juvenile myoclonic epilepsy (impulsive petit mal). [5] The seizures in these conditions are called typical absence seizures and are usually associated with generalized 3-4 Hz spike-and-slow-wave complexes on EEG. [6]

In childhood absence epilepsy, seizures are frequent and brief, lasting just a few seconds (pyknoleptic). Some children can have many such seizures per day. In other epilepsies, particularly those with an older age of onset, the seizures can last several seconds to minutes and may occur only a few times a day; these are called nonpyknoleptic or spanioleptic absence seizures.

Myoclonic and tonic-clonic seizures may also be present, especially in syndromes with an older age of onset.

In the cryptogenic or symptomatic generalized epilepsies, absence seizures are often associated with slow spike-wave complexes of 1.5-2.5 Hz [5] ; these are also called sharp-and-slow-wave complexes. These seizures may be associated with loss of axial tone and head nodding; a fall may occur. Increased tone, autonomic features, and automatisms may also be seen. Absence seizures associated with slow spike-wave complexes are called atypical absence seizures. [7]

See Epilepsy and Seizures for a general overview of these topics.


Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!