Introduction:

The pain from a headache does not start from inside the brain. (The brain itself can not feel pain.) Instead, headache pain begins in one or more of the following locations:

• The tissues covering the brain
• The structures at the base of the brain
• Muscles and blood vessels around the scalp, face, and neck

Headache is generally categorized as primary or secondary.

Primary Headache. A headache is considered primary when a disease or other medical condition does not cause it.

• Tension headache is the most common primary headache and accounts for 90% of all headaches. [For more information, see In-Depth Report # 11: Tension headaches.]
• Neurovascular headaches are the second most common primary headaches. This type includes migraines and cluster headaches. [Fore more information, see In-Depth Report # 99: Cluster headaches.] Such headaches are caused by an interaction between blood vessel and nerve abnormalities.

Headaches are usually caused by muscle tension, vascular problems, or both. Migraines are vascular in origin, and may be preceded by visual disturbances, loss of peripheral vision, and fatigue. Over-the-counter pain medications can relieve most headaches.

Secondary Headache. Secondary headaches are caused by other medical conditions, such as sinusitis, neck injuries or abnormalities, and stroke. About 2% of headaches are secondary headaches caused by abnormalities or infections in the nasal or sinus passages.

It is not uncommon for someone to experience a combination of headache types.

Migraine Headaches

Migraine is the most common form of disabling headache that prompts patients to seek care from doctors. Migraines are sometimes classified as occurring with aura (previously called classic migraine) or without aura (previously called common migraine).

In general, there are four phases to a migraine (although they may not all occur in every patient): The prodrome phase, auras, the attack, and the postdrome phase.

Prodrome. The prodrome phase is a group of vague symptoms that may precede a migraine attack by several hours, or even a day or two. Prodrome symptoms include:

• Sensitivity to light or sound
• Changes in appetite, including decreased appetite or food cravings
• Thirst
• Fatigue and drowsiness
• Mood changes including depression, irritability, or restlessness

Auras. Auras are sensory disturbances that occur before the migraine attack in 1 in 5 patients. Visually, auras are referred to as being positive or negative:

• Positive auras include bright or shimmering light or shapes at the edge of their field of vision called scintillating scotoma. They can enlarge and fill the line of vision. Other positive aura experiences are zigzag lines or stars.
• Negative auras are dark holes, blind spots, or tunnel vision (inability to see to the side).
• Patients may have mixed positive and negative auras. This is a visual experience that is sometimes described as a fortress with sharp angles around a dark center.

Other neurologic symptoms may occur at the same time as the aura, although they are less common. They include:

• Speech disturbances
• Tingling, numbness, or weakness in an arm or leg
• Perceptual disturbances such as space or size distortions
• Confusion

Migraine Attack. If untreated, attacks usually last from 4 - 72 hours. A typical migraine attack produces the following symptoms:

• Throbbing pain on one side of the head. The word migraine, in fact, is derived from the Greek word hemikrania, meaning "half of the head" because the pain of migraine often occurs on one side. Pain also sometimes spreads to affect the entire head.
• Pain worsened by physical activity
• Nausea, sometimes with vomiting
• Visual symptoms
• Facial tingling or numbness
• Extreme sensitivity to light and noise
• Looking pale and feeling cold

Less common symptoms include tearing and redness in one eye, swelling of the eyelid, and nasal congestion, including runny nose. (Such symptoms are more common in certain other headaches, notably cluster headaches.)

Postdrome. After a migraine attack, there is usually a postdrome phase, in which patients may feel exhausted and mentally foggy for a while.

Chronic Migraines

In some cases, patients eventually experience on-going and chronic headaches. Some doctors believe that, unless otherwise demonstrated, any chronic headache consisting of episodes of disabling pain that recur regularly over years should be considered as a migraine.

Chronic migraines may occur from overuse of migraine medications (called a rebound headache) or may develop over time (called transformed migraine).

Rebound Headache. The most common cause of chronic migraine is the rebound effect, which is a cycle caused by overuse of migraine medications. The process involves the following:

• Patients typically have taken pain medication for more than 3 days a week on an ongoing basis.
• When the patients stop taking medication, they experience a rebound headache.
• They start taking the drugs again.
• Eventually the headache simply persists, and medications are no longer effective.

Medications implicated in rebound migraines include nonprescription painkillers (acetaminophen, aspirin, ibuprofen), barbiturates, sedatives, narcotics, and migraine medications, particularly those that also contain caffeine. (Heavy caffeine use can also cause this condition.)

Transformed Migraines. In some cases, migraines themselves evolve into chronic, daily headaches called transformed migraines. Such headaches resemble tension headaches but are more likely to be accompanied by gastrointestinal distress and mental or visual disturbances and, in women, to be affected by menstrual cycles. In one study, the risk for transformed migraines were associated with other factors, including allergies, asthma, hypothyroidism, hypertension, and a daily intake of caffeine.

Other Migraine Variations

Although migraine is considered to be a specific chronic illness, it has various presentations that occur in different individuals.

Menstrual Migraines. Migraines are often tied to a womanâ ' s menstrual cycle, typically in the first days preceding or beginning menstruation. Researchers think that estrogen plays a role. About half of women with migraines report an association with menstruation. Compared to migraines that occur at other times of the month, menstrual migraines tend to be more severe, last longer, and not have auras. Triptan drugs can provide relief and may also help prevent these types of migraines.

Ophthalmoplegic Migraine. This very rare headache tends to occur in younger adults. The pain centers around one eye and is usually less intense than in a standard migraine. It may be accompanied by vomiting, double vision, a droopy eyelid, and paralysis of eye muscles. Attacks can last from hours to months. A computed tomography (CT) or magnetic resonance imaging (MRI) scan may be needed to rule out an aneurysm (a rupture blood vessel) in the brain.

Retinal Migraine. Symptoms of retinal migraine are short-term blind spots or total blindness in one eye that lasts less than an hour. A headache may precede or occur with the eye symptoms. Sometimes retinal migraines develop without headache. Other eye and neurologic disorders must be ruled out.

Basilar Migraine. Considered a subtype of migraine with aura, this migraine starts in the basilar artery, which forms at the base of the skull. It occurs mainly in young people. Symptoms may include vertigo (the room spins), ringing in the ears, slurred speech, unsteadiness, possibly loss of consciousness, and severe headaches.

Familial Hemiplegic Migraine. This is a very rare inherited genetic migraine disease. It can cause temporary paralysis on one side of the body, vision problems, and vertigo. These symptoms occur about 10 - 90 minutes before the headache.

Status Migrainosus. This is a serious and rare migraine. It is so severe and lasts so long that it requires hospitalization.