Headache associated with visceral disorders is "parasympathetic referred pain"

Referred pain from visceral organs tends to be expressed on the specific area of body surface, called as Head's zone. Although it is well known that sympathetic referred pains of viscera appear on the body trunk, the fact that parasympathetic referred pains exist and are expressed on the head, sacrum and posterior thigh is not appreciated properly. Functional gastrointestinal diseases accompany frequently headache, and cyclic vomiting and recurrent abdominal pains in childhood progress to migraine later. Such clinical observations on relationship between headache and viscera suggest that longstanding disease processes of viscera could induce central sensitization of trigeminocervical nuclear complex, and express "parasympathetic referred pain" on the head, like sympathetic referred pain on the body trunk, that is headache.