Neurology February 2009 Volume 72 Issue 5

Migraine attacks sometimes increase in frequency over time. Headache experts conceptualize this process with a model that envisions transition into and out of four distinct states: no migraine, low-frequency episodic migraine (<10 headaches per month), high-frequency episodic migraine (10-14 headaches per month), and chronic migraine (CM, >=15 headaches per month). Transitions may be in the direction of increasing or decreasing headache frequency and are influenced by specific risk factors. Overall, population studies estimate that patients who have low-frequency episodic migraine or high-frequency episodic migraine will transition to CM at the rate of about 2.5% per year. Two longitudinal population studies, the Frequent Headache Epidemiology study and the ongoing American Migraine Prevalence and Prevention (AMPP) study provide longitudinal population data that has defined the rates of and risk factors for transition. Launched in 2004, the AMPP study has followed a sample of >10,000 migraine sufferers annually for 4 years. Cross-sectional data from the Frequent Headache Epidemiology study and the AMPP study show that patients with chronic daily headaches have lower levels of education and household income. In addition, epidemiologic profiles show that CM sufferers tend to be older and have higher body mass indexes. These studies have also assessed a number of potential risk factors associated with the transition to CM. These include baseline high attack frequency, obesity, stressful life events, snoring, and overuse of certain classes of medication. In particular, opiate and barbiturate combination products contribute to migraine progression, and nonsteroidal anti-inflammatory agents are protective in patients with <10 headache days per month. The influence of medication is modified by both headache attack frequency and frequency of medication use. Although depression and anxiety are associated with an increased risk of new-onset CM, the influence of depression is accounted for by migraine disability assessment scale score, whereas the effect of anxiety may be independent of migraine disability assessment scale score. Emerging data on the longitudinal risk of CM suggest that, in a population at risk, CM may be a preventable disorder.(C)2009AAN Enterprises, Inc.

Comparator studies that assess treatment effects in a clinical setting have improved the understanding of the efficacy and tolerability of prophylactic treatments for chronic migraine (CM). It is premature to recommend device-based treatments, such as occipital nerve stimulation, vagal nerve stimulation, and patent foramen ovale closure for CM, because clinical trials are in the preliminary stages. Physical therapy techniques, like applying heat or cold packs, ultrasonography, and electrical stimulation, have been shown to lessen pain. Nonpharmacologic treatments, including cognitive behavioral therapy, stress management, and biofeedback, have been investigated and proved effective in some areas of pain management, including migraine. However, pharmacologic interventions may be necessary for effective, long-term prophylaxis. Several medications under investigation, including topiramate, gabapentin, tizanidine, and amitriptyline, have proved efficacious in reducing the number of migraine episodes and the pain associated with migraine, although adverse events may prevent continued use of some agents. Evidence supports the use of botulinum toxin type A (BoNT-A) for CM, with or without medication overuse, to achieve a significant reduction in headache episodes. Efficacy of BoNT-A for CM is comparable with or better than that of valproate and topiramate, with better tolerability. Predictors of response to BoNT-A for CM appear to include predominantly unilateral location of the headache and the presence of cutaneous or muscle allodynia. BoNT-A has been demonstrated to be safe and well tolerated, with rare discontinuations due to adverse events. Recent clinical trials indicate that rational combination therapy may have a place in treating refractory CM. Well-controlled multicenter trials are awaited.(C)2009AAN Enterprises, Inc.