Pathophysiology of Migraine Page 1

Most of us have probably heard about changes in blood vessels associated with migraine headaches. Some people have gotten that backwards, though! It might seem that blood vessels constrict during a migraine—that would seem logical, wouldn't it? But actually, just the opposite happens. The blood vessels on the surface of your brain dilate, and with each heartbeat, the blood surging through throws the dilated blood vessel wall up against your skull, resulting in that throbbing pounding pain you are so familiar with.

But is that all that happens? Far from it.

Migraine mostly happens within your brain. Several things happen at the beginning of a migraine attack, and we are not yet sure exactly what happens first, or whether one leads to another.

We know that there are waves of electrical changes that go across the brain, starting at the back and moving slowly towards the front. First there is a wave of excitation, followed by what is called spreading cortical depression. This has been known since the 1940s, when it was discovered in rabbits by a Brazilian neurologist named Leao, although it wasn't immediately associated with migraine at that time. Interestingly, though, there was another neurologist at about that time (named Lashley) who tracked the spread of his own visual auras, and found that they moved at about 2-3 mm/minute. This is about the same speed as spreading cortical depression.

We have since made an association between cortical spreading depression and migraine aura. And, in fact, we have been able to demonstrate very slow changes moving across the brain during migraine aura on both blood oxygen level dependent (BOLD) MRI studies and magnetoencephalography. These changes move at a rate consistent with the speed of cortical spreading depression. Although most of these studies have been done in migraine with aura, there is one PET study done in a single patient who has migraine without aura showing slowing of blood flow in a similar pattern, suggesting that cortical spreading depression may occur in migraine without aura as well. Obviously, it is much harder to study in migraine without aura, as it is more difficult to determine when the beginning of the attack is in order to test it.

There is also evidence of brainstem activation at the beginning of a migraine. Areas of the brainstem show up as brightly active on PET scans in the beginning of a migraine attack. These studies have indicated that brainstem activation occurs in both migraine with and without aura.

Here's a good link with diagrams of the brainstem and other brain areas:

http://www.morphonix.com/software/education/science/brain/game/specimens/brainstem.html





	PATHOPHYSIOLOGY OF MIGRAINE Just what happens in your head during a migraine anyway? Most of us have probably heard about changes in blood vessels associated with migraine headaches. Some people have gotten that backwards, though! It might seem that blood vessels constrict during a migraine—that would seem logical, wouldn't it? But actually, just the opposite happens. The blood vessels on the surface of your brain dilate, and with each heartbeat, the blood surging through throws the dilated blood vessel wall up against your skull, resulting in that throbbing pounding pain you are so familiar with. But is that all that happens? Far from it. Migraine mostly happens within your brain. Several things happen at the beginning of a migraine attack, and we are not yet sure exactly what happens first, or whether one leads to another. We know that there are waves of electrical changes that go across the brain, starting at the back and moving slowly towards the front. First there is a wave of excitation, followed by what is called spreading cortical depression. This has been known since the 1940s, when it was discovered in rabbits by a Brazilian neurologist named Leao, although it wasn't immediately associated with migraine at that time. Interestingly, though, there was another neurologist at about that time (named Lashley) who tracked the spread of his own visual auras, and found that they moved at about 2-3 mm/minute. This is about the same speed as spreading cortical depression. We have since made an association between cortical spreading depression and migraine aura. And, in fact, we have been able to demonstrate very slow changes moving across the brain during migraine aura on both blood oxygen level dependent (BOLD) MRI studies and magnetoencephalography. These changes move at a rate consistent with the speed of cortical spreading depression. Although most of these studies have been done in migraine with aura, there is one PET study done in a single patient who has migraine without aura showing slowing of blood flow in a similar pattern, suggesting that cortical spreading depression may occur in migraine without aura as well. Obviously, it is much harder to study in migraine without aura, as it is more difficult to determine when the beginning of the attack is in order to test it. There is also evidence of brainstem activation at the beginning of a migraine. Areas of the brainstem show up as brightly active on PET scans in the beginning of a migraine attack. These studies have indicated that brainstem activation occurs in both migraine with and without aura. Here's a good link with diagrams of the brainstem and other brain areas: http://www.morphonix.com/software/education/science/brain/game/specimens/brainstem.html Copyright 2006 HEADquarters Migraine Management Inc. All Rights Reserved Headache Info: Headache Types Headache Causes Migraine Triggers Treatment Comorbid Conditions Migraine Quiz Pathophysiology Women and Headaches Men and Headaches