Headache as an initial manifestation of systemic disease

While headache frequently arises from local dysfunction, there are many systemic diseases in which headache may be the initial or sole manifestation of the underlying process. These include infectious disease, vascular disease, drug or heavy metal intoxication, metabolic abnormalities, migraine, cluster headache, headache associated with ENT disease and cranial neuralgias (these disease entities are described in detail in the International Headache Society Classification). The work up of a patient with headache must include a consideration of these entities.