Headache is one of the most common complaints encountered by physicians of all specialties. It is a complaint in more than fifty percent of all physician visits and is the seventh leading complaints at medical centers in the United States. Due to headaches five to ten percent of young adults report missing at least a part of a day's works each month. Consequently, the physician faces a major task in addressing
patient's headache complaint'. Headache accounts for over ten million outpatient visits per year in the United States. Most of the patients are often quite concerned that their headaches represent serious underlying illness^. Headache itself is a panful and often disabling disorder and it has troubled mankind fi-om the dawn of civilization. It is one of the most common symptoms in mankind (Scher, Stewart and Lipton, 1999). For these reason a systematic approach to headache classification and diagnosis is essential both for good clinical management and for useful research.
