What causes migraines?
The specific cause of migraines is not known, but there may be fluctuations in certain neurotransmitters, chemicals that send messages between brain cells. These changes may predispose some people to develop migraine headaches.
What are the risk factors for migraine?
Up to 25% of people experience a migraine headache at some point in their life. Most migraine sufferers are female. It is estimated that after adolescence, the ratio of female to male patients who experience migraines is about 3:1. There seems to be a genetic predisposition to migraine, as there is often a strong family history of migraine in patients with this disorder.
What are the signs and symptoms of migraines?
The most common symptoms of migraine are:
- Severe, often "pounding," pain, usually on one side of the head
- Nausea and/or vomiting
- Sensitivity to light
- Sensitivity to sound
- Eye pain
The International Headache Society defines episodic migraine as being unilateral, pulsing discomfort of moderate-to-severe intensity, which is aggravated by physical activity and associated with nausea and/or vomiting as well as photophobia and/or phonophobia (sensitivity to light and sound). A migraine headache typically lasts for several hours up to several days.
Many patients describe their headache as a one-sided, pounding type of pain, with symptoms of nausea and sensitivity to light, sound, or smells (known as photophobia, phonophobia, and osmophobia). In some cases, the discomfort may be bilateral. The pain of a migraine is often graded as moderate to severe in intensity. Physical activity or exertion (walking up stairs, rushing to catch a bus or train) will worsen the symptoms.
Up to one-third of patients with migraines experience an aura, or a specific neurologic symptom, before their headache begins. Frequently, the aura is a visual disturbance described as a temporary blind spot which obscures part of the visual field. Flashing lights in one or both eyes, sometimes surrounding a blind spot, have also been described. Other symptoms, including numbness or weakness along one side, or speech disturbances, occur rarely.
Eye pain which is different from sensitivity to light is not a common component of migraine. If eye pain is a persistent symptom, or if eye pain is present and accompanied by blurred vision orloss of vision, then prompt evaluation is recommended.
In comparison, a tension headache is described as being bilateral and the pain is not pulsating, but feels like pressure or tightness. While severity can be mild-to-moderate, the headache is not disabling and there is no worsening of the pain with routine physical activity; additionally, there is no associated nausea, vomiting, photophobia, or phonophobia.
No specific physical findings are found when patients are experiencing a routine migraine headache. If an abnormality is identified on physical examination, there should be suspicion of another cause for the headache.
How are migraines diagnosed?
According to the International Classification of Headache Disorders II (ICHD-II) criteria for migraine without aura, a patient must have had at least five headache attacks fulfilling the following criteria:
- Headache attacks lasting 4 to 72 hours (untreated or unsuccessfully treated)
- The headache has at least two of the following characteristics:
- Unilateral location
- Pulsating quality
- Moderate or severe pain intensity
- Aggravation by or causing avoidance of routine physical activity (for example, walking or climbing stairs)
- During the headache, at least one of the following characteristics:
- Nausea and/or vomiting
- Photophobia and/or phonophobia
- The headache cannot be attributed to another disorder
Imaging the brain with an MRI and CT scans or performing a brain wave test (electroencephalogram [EEG]) is not necessary if the patient's physical examination is normal.
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