Migraine Clue Found in Gene Variant

Our understanding of what causes migraines has moved a step closer with the publication of a large European study.

The study is the first genome wide association study of migraine risk factors, and is published online in this week's issue of Nature Genetics.

Migraine is a neurological disorder affecting 8 percent of males and 17 percent of females and is characterized by recurrent attacks of severe headache. There are approximately 300 million people worldwide who experience a migraine attack daily.

Existing treatments can help control the symptoms, but don't cure the condition.

It's thought that people who experience migraines may have an inherited abnormality in the nerves and blood vessels in the brain.

The headache associated with migraines may be caused by blood vessels dilating abnormally, and the aura -- blind spots, flashes of light and abnormal sensations experienced before the headache -- may be caused by slow electrical waves spreading out across the brain from where the migraine originates.

Unlike other neurological conditions such as epilepsy, very little is known about what predisposes a person to migraines, although genetic factors are known to play a part.

Researchers at the International Headache Genetics Consortium scanned the genomes of approximately 5000 European people who had been diagnosed with various forms of migraines, and compared them with a control group of non-migraine sufferers.

They found those who suffered from migraines were much more likely to have a genetic variant known as a single nucleotide polymorphism (SNP).

The SNP -- called rs1835740 -- is thought to be significant because it is located between two normally-occurring genes known to be strongly associated with the production of the neurotransmitter glutamate.

Glutamate has in turn been strongly associated with migraine and is thought to be the neurotransmitter involved in the electrical waves that cause the aura.

The researchers say further work is to needed to prove their hypothesis. But they hope genetic variants such as rs1835740 could in the future be used to identify people prone to migraines.

Once the underlying pathways are better understood, they can be given specific treatments to correct the underlying abnormality, the researchers say.

Natalie Colson, who was not involved in the study, is a specialist in migraine gene studies at the School of Medical Science at Griffith University in Brisbane.

She says rs1835740 itself probably isn't part of the abnormalities causing migraines, but is simply a marker for them.

Colston believes it's likely there are several abnormal genes involved in causing migraines.

"Some people may have certain genes that make them susceptible to migraine and others will have other genes that make them susceptible, which would explain why migraine varies so much in different people," she said.

Colson says although a genetic predisposition is important, there are many environmental factors that may trigger migraines, such as certain foods, alcohol or flashing lights.

Ultimately, discovering what causes migraines may involve more than just decoding abnormal genes.