atypical absence seizure true behavior_ontology An atypical absence seizure has less abrupt onset and offset of loss of awareness than typical absence seizures. They are often associated with other features such as loss of muscle tone of the head, trunk or limbs (often a gradual slump) and subtle myoclonic jerks. Atypical absence seizures often occur in individuals with intellectual impairment.The loss of awareness may be minimal with the patient continuing an activity, but more slowly or with mistakes. George Gkoutos "An absence seizure not induced by hyperventilation." [NBO:GVG] 2011-05-28T11:59:31Z HP:0007270 generalized non-motor onset seizure