Chronic daily headache (CDH) refers to a broad range of headache disorders occurring greater than 15 days a month - in many cases daily - for a period of at least 3 months. The primary variety of chronic daily headache is further subdivided into two distinct categories: headaches lasting more than 4 hours and headaches lasting less than 4 hours. There may be as many as 5% of the population encountering severe headaches on a daily or near-daily basis, and these individuals make up the majority of consultations to specialists.
Patients with CDH often over-use pain relief medication, which can precipitate or sustain the frequency patterns seen with CDH. Medication categories for which overuse can be a causative factor for CDH include triptans, analgesics, and ergotamines.
The primary types of CDH with average duration of greater than 4 hours include:
- chronic migraine or transformed migraine
- chronic tension type headache
- new daily persistent headache
- hemicrania continua
The primary types of CDH with duration of less than 4 hours include:
- chronic cluster headache
- chronic paroxysmal hemicrania
- SUNCT (short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing)
Current classification systems make it difficult to correctly diagnose CDH patients. In many cases, those with CDH are incorrectly given the chronic tension type headache diagnosis. A retrospective review of headache clinic patients with CDH indicated that most had CDH evolving from migraine (transformed migraine), some were of new onset, and a few had CDH that had evolved from episodic tension type headache. Most patients had CDH associated with medication overuse.
Different preventive treatment options exist for CDH, depending on the type of CDH. Most importantly is to limit analgesic use and avoid the other type of daily headache – Medication Overuse Headache.