Touching Lives - November 2006
Stars and stripes
Migraine is the most common neurological condition in the developed world, more widespread than diabetes, epilepsy and asthma combined. It affects more than 15 per cent of people in the UK, and, while some might only suffer one or two migraines in a year, others may have to deal with several migraine attacks a week, making everyday life and routine almost impossible. The World Health Organisation lists migraine among the top 20 most disabling lifetime conditions.
More than just a headache With figures like these, it is likely that we all know someone who experiences migraine, or indeed have the misfortune to suffer them ourselves. The list of rich and famous reported to have been susceptible to migraine is extensive, including Julius Caesar, Napoleon, Virginia Wolff, Elvis Presley and Princess Margaret, but what exactly is a migraine and how is it distinguished from a plain old headache?
Well, experts measure the symptoms against a number of criteria before confirming a migraine diagnosis. Firstly, unmedicated, the pain should last for more than four hours, and demonstrate at least two of the following characteristics: the pain should be throbbing or pulsating; it should be on one side of the head rather than all over; it should be intense enough to prevent you from carrying out normal activities, and may be exacerbated by activity even as basic as standing up or climbing stairs.
As if that weren’t bad enough, a migraine may also bring with it nausea, photophobia and phonophobia — intolerance to light and sounds that would ordinarily not be uncomfortable. In fact, a headache must be accompanied by either nausea or photo and phonophobia to be classified as a migraine.
Any plausible explanation for the headache — a fever, dehydration — will rule out a migraine diagnosis. It must literally appear out of the blue.
Seeing stars Alongside these ‘measurable’ attributes, some people experience additional neurological symptoms that are more transient and difficult to monitor, and are often connected to vision. These sensory disturbances are known as the ‘migraine aura’, and are for many sufferers the first dreaded indication that a migraine attack is on its way.
Stars, zigzag lines and shimmering dots are all commonly described by migraine patients who experience a visual aura, usually about 30 minutes before the migraine itself develops. Others report double vision, loss of vision, tunnel vision and even distortions where objects or people appear to grow, shrink or change shape, becoming disproportionate before their very eyes. This is known as the ‘Alice in Wonderland effect’ because it is thought to have been the inspiration for the classic children’s story written by Lewis Carroll, himself a migraine sufferer.
It was these intriguing symptoms that sparked Dr Alex Shepherd’s interest in this area of research. Dr Shepherd admits to “a basic interest in all things visual”, and the altered vision that is so commonly a part of the migraine aura certainly suggests that the visual system is involved.
Visual triggers Dr Shepherd is based at Birkbeck College in London and is a leading authority on migraine. The £26,863 grant from Action Medical Research, awarded in 2003, enabled Dr Shepherd and her colleague, Dr Marc Tibber, to compare the visual processes of people who suffer migraine with people who do not, leading to some interesting discoveries.
Dr Shepherd says,”Symptoms such as photophobia and the visual aura clearly show that during a migraine attack the visual system is involved. However, there are also signs that vision is disturbed in between migraine attacks as well. One clear indicator of this is the fact that visual patterns can actually trigger a migraine in up to 60 per cent of patients.
“Stripes, flickering lights, bright reflections — these are all the sorts of things that people report will set off their migraine. If you think for a moment about how many times you meet these things in your daily life, you get some idea of how precarious life can be for someone whose migraines can be triggered by visual patterns.”
Dr Shepherd was determined to find out how these visual triggers could actually result in a migraine. She and Dr Tibber recruited over 300 volunteers, some migraine sufferers and some non-sufferers to act as a control group.These volunteers undertook a number of visual exercises, designed to test particular stages of the visual processing system, which involved looking at a variety of displays containing elements of motion, stripes, colours and shapes.
The team measured various aspects of what the participants saw, both while they were studying the image in front of them and after the image had been taken away. They found that there were differences between people with and without migraine at every stage.
For example, when looking at repetitive striped patterns, people with migraine tended to see more, and more vivid, illusions.They also found them very unpleasant to view.Those who suffer visually-triggered migraine performed most differently of all the volunteers.The doctors also found that those who saw the most vivid illusions also performed the most differently on other visual tests that examined the ability to see feint stripes, colour, motion and flicker. These findings show that there are clearly widespread differences in the visual system in migraine, which are greatest in those whose migraines can be triggered visually.
Several of the tests revealed that if differences became more pronounced if more time had elapsed since the last attack. In particular, one visual illusion, the motion after-effect, lasted longer in those who suffer migraine, and longer still in those who had not had a recent attack.
Dr Shepherd comments,”The most interesting result is that on some of the tasks, performance depended on how long it had been since the last migraine, with those who hadn’t had one for a while performing most differently to the control group.This is consistent with the idea that there is a slow build up of changes that result in a migraine.”
Averting attack Dr Shepherd’s ultimate intention is to be able to help migraine sufferers predict when an attack may be imminent, and thus avoid it.To this end, and with knowledge gained from this research, she is now planning to study individuals over a period of time, known as a ‘longitudinal’ study, to monitor this ‘build up’ and look at the possibility of developing tests that could predict migraine.
She says,”Once we have the results of this longitudinal study, and have established whether there are systematic changes in relation to migraine proximity (i.e. when the last migraine occurred), we should be in a position to produce a test that patients can use at home to see whether an attack is due.We also plan to put together some guidelines advising on what preventative measures they should take to stop that migraine taking hold. These might include getting an early night, avoiding stress, or, for those whose migraines respond to visual stimuli, tailoring their environment so that they don’t encounter stripes, bright lights, flicker and so on.”
Dr Shepherd needs to recruit 20 or more volunteers to the longitudinal study, but once this is done, it could be only a matter of months before the selfassessment tests and guidelines are developed. She concludes, “This could transform the lives of the millions of people who live in constant fear of their next migraine.” TL
We express our thanks to Dixons Foundation, John Lewis Partnership and SEARCH for generously donating towards this research.