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Pain on one side of the head

Migraine pain on one side of the head: An introduction

Although migraines may cause pain all over the head, often the pain starts or is concentrated on one side. Pain on one side of the head is called unilateral pain. (When the pain is on both sides it is referred to as bilateral pain). More than half – about 59 percent – of migraine suffers complain that pain is on one side of the head according to the American Migraine Study II of almost 4,000 migraine sufferers in 1999.

In fact, the term migraine came from the Latin word hemicrania, which meant pain on one side of the head, or cranium. Some sufferers say the migraine attacks always happen on the same side, in others it may occur on either side and still there are those whose pain covers the head.

Studies have shown that the presence of pain on one side of the head is about the same whether the migraine occurs with or without aura – 58.1 percent for those with aura, and 60.3 percent for those without aura. Most studies include pain on one side of the head in the definition of migraine.

What happens to your brain when you have a migraine?

The answer varies depending on the person and sometimes varies with each migraine episode.

Frequently, migraine sufferers who experience migraine aura, a vision change that occurs in some before migraine pain, have one-sided pain. This may come from the changes in blood flow in the brain on one side, which scientists blame for aura and pain.

Uneven dysfunction in the brain stem may also be blamed for the one-sided migraine pain, according to a 2005 study that scanned the brains of patients as they suffered from a migraine. Researchers said the location of the disruption in brain function determines what part of the head hurts with migraines. The study found increased activity in part of the brain stem called the dorsolateral pons. For example, those with pain only on the right side of the head had more activity in the right side of the dorsolateral pons. The same was seen for those who only had pain from migraine on the left side, more action was seen on the left side of the brain stem.


Written by: Otesa Miles | Last review date: November 2010
U.S. Dept. of Health and Human Services