High-frequency headaches of long duration include chronic migraine, chronic tension-type headache, new daily persistent headache, and hemicrania continua. Medication overuse is common, being present in more than 80% of chronic migraine patients in subspecialty clinics but in only 30% of chronic headache sufferers in population studies (Evers and Marziniak 2010). Patients with chronic migraine seek care when they have a superimposed full-blown migraine (exacerbation). When a clear history is obtained, investigation is not required.
New daily persistent headache is characterized by the abrupt onset of a chronic daily headache. It is classified as a primary headache disorder, although a viral prodrome may precede the onset, suggesting that some syndromes may actually be secondary despite the lack of an obvious demonstrable cause. When patients with acute headache first seek care with this syndrome, thorough investigation is necessary to exclude secondary disorders (Mack 2009).
Hemicrania continua is commonly mistaken for chronic migraine (Peres et al 2009). Both disorders are characterized by chronic unilateral pain with superimposed painful exacerbations. In hemicrania continua, the exacerbations are often associated with ipsilateral autonomic features, such as conjunctival injection, lacrimation, and ptosis. In chronic migraine, exacerbations are more typically accompanied by nausea, photophobia, and phonophobia. In addition, patients with hemicrania continua usually do not have an antecedent history of episodic migraine. Chronic migraine attacks increase in frequency over time. If the headaches are longstanding, the patient may not remember how they began. Though pain fluctuates in hemicrania continua, it does not usually have the morning and end-of-dosing-interval pattern of exacerbations typical of chronic migraine. It is advisable to offer patients with unilateral chronic daily headache a therapeutic trial with indomethacin (doses of up to 225 mg/day for 3 to 4 days) prior to other intervention.