New theory on cause of migraine
New study suggests that we have been misunderstanding the cause of migraine headaches for decades.
Danish researchers have taken a crucial step toward a new explanation of where and why it hurts when we have a migraine.
This throbbing pain in the head, which is usually accompanied by other symptoms such as nausea and sensitivity to light and sound, has been puzzling scientists for centuries.
The new discovery represents a break with the prevailing theory in recent decades:
“This turns on the head our existing ideas of the mechanisms behinds migraines. For many years it was thought that the pain was caused by expanded blood vessels outside the skull,” says Professor Jes Olesen, of The Danish Headache Center (DHC), Glostrup Hospital, Denmark, who co-authored the new study, published in The Lancet Neurology.
When scans show that the blood vessels do not expand, there must be another reason why the patients get headaches.
“When scans show that the blood vessels do not expand, there must be another reason why the patients get headaches.”
Less arterial expansion than expected
The article is based on experiments designed to identify which arteries expanded during a migraine attack, headed by Faisal Mohammad Amin, a doctor and a PhD student at the DHC.
Using the latest MRI scan technology, Amin examined the inside and outside of the brain and looked at small arteries during natural attacks.
- A total of 19 healthy women with migraine took part in the experiment.
- Their brains were scanned while they suffered a severe migraine headache without aura, headaches that are limited to one side of the head.
- The scans enabled the researchers to compare the expansions of the blood vessels on the side where the pain was felt with the side where no pain was felt.
Migraine sufferers usually experience a severe headache, which feels like a throbbing pain at the front or on one side of the head. This pain is usually accompanied by several autonomic nervous system symptoms.
Migraine pain is further aggravated by movement, for instance if you bend your head forward or climb stairs.
It is therefore not uncommon to hear complaints from migraine patients who worry that their head is about to explode. The new study shows that such worries are unfounded.
“Contrary to what has previously been believed, we found that the arteries on the outside of the skull did not expand during migraine attacks,” says Amin.
“Arteries inside the skull were only slightly expanded on the side where the headache was felt, compared to the other side where no pain was felt.”
Migraine drugs don’t work like we thought they did
The pain-ridden women were then given a popular migraine drug to determine how it affected the arteries.
“We treated the attacks with sumatriptan, which is the most popular migraine drug on the market. And then we made another MRI scan of the brain,” explains Amin.
The word ‘migraine’ derives from the Greek ἡμικρανία (hemikrania), ‘pain on one side of the head’, from ἡμι- (hemi-), ‘half’, and κρανίον (kranion), ‘skull’.
“Here we observed that the arteries inside the brain remained expanded even after the migraine headache had passed.”
This suggests that the old theory that sumatriptan works by narrowing the arteries may not be right after all. The new findings prepare the ground for studies into why sumatriptan still works even though the beneficial effect does not appear to be linked to the narrowing of arteries.
New theory: pain caused by extra-sensitive nerve fibres
The new discovery has paved the way for a new theory: migraine pain occurs because the nerve fibres around the blood vessels become extra sensitive.
This means that the blood’s normal pulsation in an artery feels like an intense, throbbing pain. If this is the case, it is as yet uncertain why it is so.
“Our findings are of great importance to our understanding of migraine headaches and future research on migraines,” says Amin.
“At the same time, the findings can also be used to reassure migraine sufferers who worry that their arteries are about to explode during an attack. They’re not.”
Colleagues are impressed
Helge Kasch, a headache researcher Aarhus University’s Department of Clinical Medicine – Department of Neurology, sees great potential in the new study:
“The findings indicate that a change occurs in the nervous control of the blood vessels locally in the brain, and at the same time there is a change in the pain regulation,” he says.
”Future medical treatment should also seek to ensure that the drug will function inside the central nervous system/the brain and must be able to pass the blood-brain barrier.
“Non-medical treatments may eventually manage to modulate these systems from other angles.”
Read the Danish version of this article at videnskab.dk
Translated by: Dann Vinther
- 'Magnetic resonance angiography of intracranial and extracranial arteries in patients with spontaneous migraine without aura: a cross-sectional study,' The Lancet Neurology, 9 April 2013. doi:10.1016/S1474-4422(13)70067-X