Less common varieties of migraine are the so-called migraine equivalents and unusual varieties of complicated migraine. "Migraine equivalent" is a term used to denote conditions or symptomatology believed to be migrainous in origin but without the typical history of either classic or common migraine headache. The most well-recognized type of migraine equivalent is abdominal migraine, in which cyclical vomiting, periodic attacks of nausea, or abdominal pain occur (usually in children or in adolescents). These patients experience more typical attacks of migraine in later life. If the past history of migraine patients is investigated, a history of cyclical vomiting is far more commonly found than in a control headache population. Very rarely true abdominal migraine occurs in adult life. In this situation there may be sudden severe abdominal pain with vomiting and even abdominal rigidity. The usual brevity of the attack or previous similar benign episodes or strong history of migraine help confirm the diagnosis. Other migraine equivalents include periodic diarrhea, fever, mood changes, and possibly attacks of chest pain known as precordial migraine. Acute confusional states have been attributed to migraine in juveniles.