The focus is on the fluid-filled microcavities that surround blood vessels in the brain and which appear altered in severe migraine sufferers. They may become the target of new therapies.
148 million people in the world suffer from chronic migraine, a type of headache featuring recurring crises, nausea, light sensitivity or light phobia, dizziness and intense pain, triggered by a multitude of stimuli. This condition is often debilitating and, up to now, treatment has always been unsatisfactory, partly due to a lack of understanding of the phenomenon.
Now, however, a new study - presented at the annual meeting of the Radiological Society of North America by neurologists from the Keck School of Medicine at the University of Southern California in Los Angeles - could allow major progress to be made. For the first time this study sheds light on some never-before-described features, offering an explanation of what happens during a migraine.
Chronic migraine: does the cause lie in perivascular spaces?
To study changes when a migraine occurs, researchers used a particularly powerful and sensitive MRI, called 7T, to analyse a very specific part of the brain’s anatomy: perivascular spaces.
These are tiny fluid-filled areas located around the blood vessels, especially near the basal ganglia (as it is known in technical terms), white matter and optic nerves. These areas can present abnormalities, especially when the cells of the vessels themselves are inflamed, or where there is a defect (like permeability), i.e. when a small vessel or capillary pathology is present. As the vessels and the perivascular spaces have a very close relationship, and as it is known that a headache is caused by abnormalities of the vessels (and not of the nerve cells - the brain has no pain terminals), the idea was to study the phenomenon indirectly, with a detailed analysis of changes in the spaces and the fluid they contain.
This is why researchers studied ten chronic migraine suffers, ten people with sporadic migraines with auras and five healthy control people (all aged between 25 and 60, with no neurological or psychiatric pathologies that could affect or confuse the results) under the 7T MRI. They measured specific parameters, like the size of the perivascular spaces, any micro-bleeding from the vessels, and areas with a high signal intensity. They then compared the data with each participant’s clinical history and circumstances, and with the migraine features, like whether or not there is an aura, migraine duration, intensity and triggers (the stimuli that cause the migraine) as well as the exact location of the pain.
Larger and more widespread spaces
Finally, it emerged that migraine sufferers have more numerous and larger perivascular spaces than non-sufferers, with areas of radiological hyper-intensity in their white matter (which, in turn, signal micro-lesions).
The 7T MRI of migraine suffers is therefore very characteristic. The general MRI picture is that of a damaged glymphatic system, i.e. the complex system of interchange between the blood vessels and their external spaces, which drains cellular waste (whole or fragments of proteins, and other substances to be eliminated), which should not accumulate.
Valuable MRI maps
Something is not working properly in migraine sufferers, and both damage to the vessels and excess fluid can be seen, although it is not clear what the relationship is between the two phenomena, i.e. what is the cause and what is the effect.
However, if nothing else, a specific MRI map is now available (which will have to be confirmed on a larger number of patients), from which researchers can begin to investigate everything that remains to be understood, which may include the effect of targeted therapies, and the distinct features of different types of migraine.