It has long been known that migraine sufferers experience increased, or extreme, sensitivity to light and sound, and a new study from the Universities of Birmingham and Lancaster could finally explain why.
Migraines are a neurological condition characterised by intense, debilitating and persistent headaches. An estimated 6 million people suffer from migraines in the UK, approximately 11 per cent of the total population.
The study found that people who suffer from migraine headaches appear to have a hyper-excitable visual cortex.
“Most migraineurs also report experiencing abnormal visual sensations in their everyday life, for example, elementary hallucinations, visual discomforts and extra light sensitivity,” said lead author Dr Terence Chun Yuen Fong.
Although much is still to be understood about the exact cause of these headaches, this study has, for the first time, provided evidence that migraines are linked with abnormalities in the visual cortex, the part of the brain that receives, integrates and processes visual information from the retinas.
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An experiment was carried out on a group of 60 volunteers, half of whom regularly suffered from migraines. The study examined responses from visual stimuli, where participants rated a striped grating pattern according to whether it was uncomfortable to look at, or any associated visual phenomena they had.
The researchers carried out an electroencephalogram (EEG) to measure the electrical activity of the brain, allowing them to track and record specific brain response patterns.
Results from both tests agreed. A larger response was found in the visual cortex among the group or migraine sufferers when compared to the group of non-migraine sufferers. However, the study also found hyper-excitability in the visual cortex in a subgroup of non-migraineurs; those who had reported additional visual disturbances but did not experience migraines.
“Our study provides evidence there are likely specific anomalies present in the way the visual cortex of migraine sufferers processes information from the outside world,” said senior author Dr Ali Mazaheri.
“However, we suspect it’s only part of the picture since the same patterns of activity can also be seen in non-migraineurs who are sensitive to certain visual stimuli.”
Reader Q&A: Why do some people get migraines?
Asked by: Rachel Carmichael, Leicester
Amazingly, the precise cause of migraines is still unknown. These intense headaches, often on one side and accompanied by nausea and sometimes visions of zigzag lines and extreme sensitivity to light and noise, must be caused by abnormal brain activity. But we just don’t know what kind or whether there are many different causes.
Hormonal fluctuations, especially in oestrogen, can trigger migraines. So some women suffer more during menstruation, pregnancy or menopause. Certain foods and additives can cause migraines and people who diet, skip meals or consume a lot of caffeine can suffer. Disturbed sleep and jetlag can also cause them.
One rare inherited type called familial hemiplegic migraine is caused by four specific gene mutations. More common types are also associated with many different genes that affect brain function. The simplest answer lies in the family. Up to 90 per cent of sufferers have a family history of migraines.