A Chronic Headache

A “Chronic Headache” is a headache that occurs 15 or more days in a month [3]. Chronic headaches may not be fully cured but can be well managed and controlled using various clinical and non-clinical methods [39]. Different types of headaches [64] have different symptomatic characteristics [3]. Individuals may have single or multiple types of chronic headaches at the same time. A headache attack occurs due to changes in the headache patient’s “internal” and/or “external” environment [31]. An example of internal change can be the abrupt decline in estrogen (a hormone) levels occurring with menstruations, whereas example of an external change can be the effect of weather changes. “Headache trigger” is a commonly used term to label any such “internal”