An atypical absence seizure is a type of generalized non-motor (absence) seizure characterized by interruption of ongoing activities and reduced responsiveness. In comparison to a typical absence seizure, changes in tone may be more pronounced, onset and/or cessation may be less abrupt, and the duration of the ictus and post-ictal recovery may be longer. Although not always available, an EEG often demonstrates slow (<3 Hz), irregular, generalized spike-wave activity. The phenotype is Atypical absence seizure (HP_0007270). Also known as: Atypical absence, Atypical absence seizures, Atypical petit mal seizures.