Dr Nazia Karsan
Headache Clinical Research Fellow at King’s College London
Prof Peter Goadsby
NIHR-Wellcome Trust King’s Clinical Research Facility, King’s College London
Some migraine sufferers consider they can trigger a migraine. Some have symptoms before headache, which can be mistaken for triggers. How much control over whether you have an attack or not do you really hold?
Many people with migraine identify factors, such as foods and bright lights, that they consider as triggers for their migraine attacks. Some feel a change in pattern of regular behaviour, such as altered sleep and food and drink intake, can be triggers.
We know that the brain of someone with migraine likes balance; such as regular sleep and meal patterns, and we also know that migraine can be triggered by alcohol and the menstrual cycle. The evidence for other triggers is less impressive. When researchers have tried to trigger migraine in experiments using measures such as exercise, chocolate ingestion and bright light, they have largely been unsuccessful.
Many sufferers, when prompted, can identify painless symptoms of a migraine attack starting hours to days before headache, that act as a warning of its onset. These are called premonitory symptoms. A range of symptoms have been reported including mood and cognitive change, light and sound sensitivity and food cravings.
The brain is already behaving abnormally before headache, which we know from studies of electrical activity and imaging. Given the brain areas involved during this time include those that can generate food cravings, then, for example, sweet cravings could occur before you know the attack has started. If you then eat some chocolate, and soon after develop a migraine headache, you may think that the chocolate has triggered the migraine. However, the attack had already started. In this situation, it is conceivable that the chocolate was correctly associated with the attack, but incorrectly attributed as a trigger. The same could be true for other triggers like bright light perceived as a trigger and light sensitivity in the premonitory phase, and strong smells as a perceived trigger and smell sensitivity in the premonitory phase, among others.
What causes premonitory symptoms?
While we have some understanding of the pain-generating pathways in the brain, we do not really know how the migraine attack starts in the brain and causes premonitory symptoms. We know that the brain behaves abnormally during this time, in areas that could feasibly be causing the symptoms, like mood and memory areas and the part of the brain responsible for regulation of food and water intake and sleep cycles (the hypothalamus).
The similarlity in premonitory symptoms with some reported trigger factors, the involvement of corresponding brain areas during premonitory symptoms and the general difficulty in triggering migraine experimentally, have made us think that perhaps many triggers are misperceived as early migraine attack symptoms and that avoidance of lifestyle and environmental factors may be unnecessary and unhelpful.
How much control do you have?
This leads to the question: how much control do you have over your migraine? The associated question being, is ‘trigger avoidance’ a useful treatment strategy? We would suggest detailed diary documentation of attacks, with symptoms and perceived triggers before pain, and pain onset relative to these, so that a sufferer can evaluate the reliability of a particular trigger factor, or indeed assess if it is actually associated with the corresponding premonitory symptom.
Systematic symptom capture in this way could help shape migraine therapeutics going forwards, enabling assessment of early treatment, trigger modification and attack prediction. No doubt many migraineurs can identify triggers; however, if you cannot, perhaps reflecting on early premonitory symptoms will provide understanding and new answers.