Chronic Migraine

Chronic migraine is defined as headache on more than 15 days per month in patients with migraine. Chronic migraine is difficult to treat and requires a multidisciplinary approach. Only two pharmacological treatments have been shown to be effective in placebo-controlled randomized trials: topiramate and local injection of botulinum toxin.

The International Headache Society separates primary headaches into episodic and chronic headache. Chronic headache is defined as more than 15 headache days per month for a time period of more than 3 months. Chronic migraine may be complicated by the frequent or regular use of symptomatic treatment with analgesics including opioids or specific migraine drugs (eg, ergots or triptans). This condition is termed chronic migraine with medication overuse. Medication overuse is defined as intake of simple analgesics (eg, aspirin, acetaminophen, or ibuprofen) on more than 15 days per month or the intake of combination analgesics, opioids, ergots, or triptans on more than 10 days per month.

Epidemiology

It has been estimated that chronic migraine may affect 1.3% to 5.1% of the global population. Chronic migraine is a disabling, underdiagnosed, under-recognized, and undertreated disorder; data demonstrate that it is significantly more disabling than episodic migraine. Compared to episodic migraine, patients from chronic migraine are significantly more likely to be female, disabled from employment, depressed, anxious, suffering with other forms of chronic pain, and overusing acute pain medications. Acute pain medication overuse or overuse of specific migraine medication is reported in about 66% to 75% of adults with chronic migraine.

Pathophysiology

The pathophysiology of chronic migraine is not clear. Sensitization of central trigeminothalamic pathways is considered one possibility. Dysmodulation from impaired descending inhibition or enhanced descending facilitation of nociception are possibilities. The frequent overuse of acute pain medications also may play a major role in the development of chronic migraine. Both acute pain medication overuse and migraine headache often are accompanied by cutaneous allodynia, which begins on the side of the head ipsilateral to the headache and may spread to involve the contralateral side of the head, upper torso, and extremities.

Management of chronic migraines

The management of chronic migraine requires identifying and managing risk factors (eg, sleep apnea, caffeine consumption), establishing limits on acute pain medications to less than 10 days per month, initiating nonpharmacologic treatment if appropriate, initiating preventive treatment, and assessing and treating neuropsychiatric disorders and other comorbid conditions that could contribute to increased attack frequency (eg, obesity).

Preventative treatment

The primary goals of preventive migraine therapy are to reduce the frequency and severity of attacks, to reduce reliance upon acute medications, and to improve the migraine patients’ quality of life. Reduction of attack frequency and reliance on acute medications may be particularly important in reducing the risk of the development of chronic migraine. Preventive treatment, even in the presence of acute pain medication overuse, has been shown to effectively reduce migraine frequency and disability. Drug selection should be individualized based on comorbid or coexistent illness/disorders, specifically avoiding drugs that may exacerbate another underlying condition. The choice of preventive drug should be based on evidence, though few clinical trials have investigated preventive medications over the long term or specifically for patients with chronic migraine.

Several recent randomized controlled trials evaluating the efficacy of topiramate and onabotulinumtoxin A have confirmed efficacy of these treatments for the prophylaxis of headaches in patients with CM.

Topiramate

Preventive treatment with topiramate in patients with episodic migraine may reduce the risk of developing chronic forms of headache. Low-dose topiramate may be effective in reducing headache frequency in patients experiencing chronic migraines with acute medication overuse.

Botulinum toxin injections

Boulinumtoxin A has been reported to relieve pain associated with a variety of conditions, including migraine headache. Unlike its function at the neuromuscular junction, the mechanism of action of boulinumtoxin A in nociception and migraine relief is not clear. It is postulated that boulinumtoxin A inhibits the sensitization of peripheral trigeminal sensory fibers, which modulate the activity of central trigeminal neurons, and thus, indirectly leads to the inhibition of migraine headache.

The PREEMPT trial confirmed botulinumtoxin A as an effective, safe, and well-tolerated headache prophylaxis treatment of adults with chronic migraines.

Other treatment options in chronic migraine

  • Gabapentin
  • Pregabalin
  • Amitriptyline

Summary

Chronic migraines is a highly disabling disease and treatment options are limited. Up to now, only topiramate and local injection of botulinum toxin have shown efficacy in large placebo controlled randomized trials. Both therapies are effective in patients with chronic migraines with and without medication overuse. In many patients, treatment results are unsatisfactory and other prophylactic drugs are needed.

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