What Is Chronic Migraine?

Migraines are categorized as either episodic or chronic. The differentiating factor is the frequency of the migraine attacks. Episodic migraine (EM) involves headaches that occur 14 or fewer days a month. Chronic migraine (CM) involves at least 15 headache days per month for more than three months with at least eight of the 15 days including clinical features of migraine without aura.

Episodic migraine can eventually develop into chronic migraine. Signs that episodic migraine is becoming chronic include increasing migraine attacks per month and taking increased amounts of medication per month. Chronic migraine may also remit back to episodic migraine.

Chronic migraine affects 3-5% of the U.S. population.

Symptoms

Symptoms of chronic migraine include the following:

• Moderate to intense throbbing head pain, typically on one side of the head
• Sensitivity to light, sounds or smells
• Nausea or vomiting
• Pain that is made worse by movement or routine physical activity

Causes

In general, migraine headaches are thought to be caused by genetics, hormonal changes, and environmental factors. Chronic migraine may be caused by an overuse of medications used to treat episodic migraine. These medications include barbiturate-containing medications, such as amobarbital and butabarbital, narcotics, nonsteroidal anti-inflammatory medications (NSAIDs), and acetaminophen.

Risk factors

Factors that increase the risk of developing chronic migraine include the following:

• Obesity
• Snoring or sleep apnea
• Central nervous system disorders
• Mood disorders, such as anxiety and depression
• History of brain injury or infection, such as meningitis
• Brain tumors
• Intracranial pressure that is too low or too high