Chronic Daily Headache
Chronic daily headache (CDH) is a disorder that is distressing for patients and frustrating for clinicians. The reasons why some patients may be predisposed to having chronic daily headache are not entirely clear. We now know of certain predicting factors that may indicate the likelihood of chronicity for migraine patients. Although the etiology is still not clear, current theories suggest that trigeminal pathway and brainstem are highly involved in initiating and maintaining chronicity of headache. Several studies, using newer imaging technology, already show some interesting and promising results. It is very likely that CDH, like migraine headache, is a neurovascular disorder.
Since the mechanisms underlying CDH are still not well understood, the treatment choices are open to debate. There are both pharmacologic and non-pharmacologic treatment options available to patients. As more studies on CDH are conducted, eventually we will have a better understanding of CDH. At present, it is important for clinicians to keep in mind that CDH is a disabling disease, and that promptly recognizing and treating pa-tients with headache—as early as possible—can prevent chronicity in many cases.
What would you do for a 40-year-old patient complaining of 6 months of persistent headache? The patient reports he has had a headache almost everyday; he describes it as pulsating, unilateral, and aggravated by activity. What if his headache is unilateral without side-shifting but with ipsilateral lacrimation and ptosis? What if the headache is bilateral? What if his daily headache seems to occur without any preceding events and there is no past medical history of headache? Would the diagnosis be different? More importantly, would your option of treatment for this patient be different? Discussion on answers to some of these questions will be presented in this article.
Chronic headache is a common disorder even though it is still not well understood. The overall worldwide prevalence is approximately 4%, and the female to male ratio is close to two to one. A population-based survey from 1998 to 2000 showed that 4.1% of Americans, 4.35% of Greeks, 3.9% of elderly Chinese, and 4.7% of Spaniards had primary chronic daily headaches.1 There are two peaks of age-related prevalence: 20-24 years of age and those above the age of 64 (8% for both).2
The latest diagnostic criteria for CDH were published by the International Headache Society in 2004. According to these criteria, primary chronic daily headache (CDH) is defined as headache that occurs for more than 15 days a month and has no structural or infectious causes.
CDH is further divided into four subtypes3:
- Chronic tension-type headache (approximately in 2-3% of the population)
- Chronic migraine (~2%)
- New daily persistent headache (~0.2%)
- Hemicrania continua (very rare)
Figure 1 presents a diagnostic flow diagram for classifying chronic daily headache. The most common type of headache that a clinician encounters in practice is either chronic tension-type headache or chronic migraine. These patients usually have a history of previous episodic tension, migraine headaches, or both.
New daily persistent headache (NDPH) is a new subtype recently created to describe headaches that suddenly appear one day and the patient distinctly remembers the onset. These patients usually do not have a previous history of headache. To date, we still don’t know much about the epidemiology, pathogenesis, or treatment of NDPH. [Editor’s note: see Dr. Steven Singer’s article “New Daily Persistent Headache” in this issue for a discussion of NDPH and the latest findings.]
Hemicrania continua is a rare headache disorder that is now more frequently recognized and treated by headache clinics. It is a continuous one-sided headache (sometimes with autonomic features like tearing and rhinorrhea) that completely resolves with the administration of indomethacin. It is so perfectly treatable that this condition should be considered in every CDH patient. An adequate trial of oral indomethacin over several days should be given if a CDH patient has only one-sided symptoms and is not responding to other treatment. The dose can be increased from 25mg bid to a maximum of 300mg per day.4 A single IM shot of 50mg indomethacin (the so-called Indotest) can also be used effectively.5
Risk Factors and Chronicity
Epidemiological studies have shown that migraine has a higher prevalence in households with lower socio-economic status.6 This could either be a cause factor or an effect. Having many migraines could lead to poorer health status and lower academic and social achievement since they can be quite debilitating. Who therefore has a higher risk of having CDH? Although there are limited data on the natural course of CDH, a few risk factors for CDH have been identified.
The risk factors that have been found to be associated with CDH include female gender, white race, lower educational level, being previously married (e.g. divorced, widowed, or separated), and obesity.7 Conversely, the factors associated with remission are non-whites, higher education level, and being currently married. These risk factors were identified by Scher et al who surveyed 55,255 potential cases and controls in the Baltimore, Philadelphia, and Atlanta metropolitan areas between 1997 and 1999.7 Scher et al collected information on gender, age, height, weight, current marital status, highest educational level, and race—as well as duration of CDH, pre-CDH frequency, and the speed of onset of CDH. The authors followed up with 798 controls and 1134 cases of patients who were able to provide their headache frequency. The one-year incidence of new-onset CDH was reported at 3%.9 This study found that the likelihood of remission increased with age for women but not for men—suggesting that the natural history of CDH might be different in men and women.7 This likelihood may be explained by the fact that the majority of women stop having migraines after menopause.
Scher et al also found that controls with higher headache frequency, obesity, or arthritis were all more likely to have new-onset CDH at follow-up.7 Moreover, the risk of new-onset CDH was significantly higher in control subjects with more than two headaches per month.7 It is therefore important for clinicians to promptly treat patients with frequent headaches to prevent progression to CDH. Scher et al, also reported that 16% of CDH subjects reported continuous headaches.7 Patients who had continuous headaches were often older and had experienced CDH for a longer duration. The authors hypothesized that “if there is such a thing as a progressive headache syndrome, then continuous headache may represent a later stage of the disorder.”7