Scientists believe people suffering from migraines may be experiencing brain damage, which could account for the higher instances of stroke among migraine sufferers.

Researchers at the University of Rochester Medical Centre have found that the debilitating headaches cause swelling in parts of the brain, leaving them starved for oxygen.

Scientists studied the wave of changes in the brain cells of mice during the onset of a migraine using imaging technology.

"In mice, the damage from these episodes looks exactly like the damage that occurs to the brain from repeated TIAs, or transient ischemic attacks," Takahiro Takano, one of the authors of the paper, said in a statement.

During a migraine, the brain uses copious amounts of energy as it attempts to restore the chemical imbalance brought on by the initial wave of cell change known as cortical spreading depression.

The CSD change occurs in the brain during migraines, stroke and head trauma.

Even though the brain's arteries expand to make more oxygen-rich blood available to meet the demand for energy, some parts of the brain still experience a severe oxygen shortage.

The shortage causes the nerve cells in the brain to become damaged, similar to someone who has suffered a head injury or who has lost blood flow to the brain because of a heart attack or a mini-stroke.

"It's long been known that patients having a migraine attack are functionally impaired from the pain. It's also been shown recently that with repeated migraines, a person's cognitive abilities decrease. But actually doing damage to the brain -- that is a surprise," Takahiro said.

For this reason, scientists say it is imperative for migraine sufferers to take their preventative medication and to avoid triggers, such as stress or lack of sleep, in an effort to prevent further headaches.

"It's astounding just how many migraine sufferers do not see a doctor and are not on a medication to prevent a recurrence," Deborah Friedman, professor of ophthalmology and neurology who was involved in the study said.

"It's estimated that less than 20 per cent of people who should be on preventive treatment receive such treatment. Doctors and patients need to be diligent and rigorous about using preventive medications for migraine."

Migraines are usually preceded by "auras," which manifest themselves in either flashes of light or black floating spots.

Scientists report that one quarter of people who suffer from migraines experience auras.

One study reported women who experience auras before a migraine have a 50 to 70 per cent higher risk of stroke compared to other women.

Doctors involved with the study noted that once someone experiences pain, the damage to the brain may well be underway.

Migraine Canada estimates nearly 3 million Canadians suffer from migraines annually.

Statistics Canada reported in 2001 that migraines are most prevalent among 25 to 54-year-olds and individuals in low-income households.