Friday, February 5, 2010

Migraines: Dilation/Constriction of Blood Vessels

A migraine begins when, for some reason, blood vessels in the brain constrict temporarily. When that happens, the amount of blood and oxygen flowing to the brain drops. So the brain sends a message: "Hey guys, we need some more blood and oxygen here!"

That causes other blood vessels to dilate. When those blood vessels expand, they become inflamed, throb, and cause the pounding pain. Because it involves changes in blood vessels, a migraine is a referred to as a vascular headache.

Vascular theory

Cortical_spreading_depression Migraines begin when blood vessels in the brain contract and expand inappropriately. This may start in the occipital lobe, in the back of the brain, as arteries spasm. The reduced flow of blood from the occipital lobe triggers the aura that some individuals who have migraines experience because the visual cortex is in the occipital area.

When the constriction stops and the blood vessels dilate, they become too wide. The once solid walls of the blood vessels become permeable and some fluid leaks out. This leakage is recognized by pain receptors in the blood vessels of surrounding tissue. In response, the body supplies the area with chemicals which cause inflammation. With each heart beat, blood passes through this sensitive area causing a throb of pain.

The vascular theory of migraines is now seen as secondary to brain dysfunction.

Serotonin and Blood Vessels

Serotonin is a type of neurotransmitter, or "communication chemical" which passes messages between nerve cells. It helps to control mood, pain sensation, sexual behavior, sleep, as well as dilation and constriction of the blood vessels among other things.

Low serotonin levels in the brain may lead to a process of constriction and dilation of the blood vessels which trigger a migraine. Triptans activate serotonin receptors to stop a migraine attack.

Neural theory

When certain nerves or an area in the brain stem become irritated, a migraine begins. In response to the irritation, the body releases chemicals which cause inflammation of the blood vessels.

These chemicals cause further irritation of the nerves and blood vessels and results in pain. Substance P is one of the substances released with first irritation. Pain then increases because substance P aids in sending pain signals to the brain.

Unifying theory

Both vascular and neural influences cause migraines.

  1. stress triggers changes in the brain
  2. these changes cause serotonin to be released
  3. blood vessels constrict and dilate
  4. chemicals including substance P irritate nerves and blood vessels causing pain

Magnesium is a dietary mineral that helps regulate blood vessel size, serotonin function, and nerve activity in the brain, among other functions.

Magnesium deficiency is thought to be at least one important factor in migraine attacks. Many studies suggest that magnesium might be a common denominator in both the vascular and the neural theories of migraine.

  • In support of the vascular theory, magnesium deficiency results in blood vessel constriction and adding magnesium to the diet leads to the opening (dilation) of blood vessels.
  • In support of the neural theory, magnesium deficiency has been linked with the production and release of substance P12-a biochemical that contributes to the inflammation of nerves and headache pain.

Recent studies indicate that having lower than normal levels of the mineral magnesium can influence serotonin and nitric oxide release, blood vessel size, and inflammation. It’s also thought that people with mitral valve prolaspe have lower than normal levels of magnesium.

Several studies have shown that magnesium depletion plays a critical role in blood vessel size. It seems not only to cause blood vessel constriction but to make blood vessels more sensitive to other chemicals that cause constriction and less sensitive to substances that cause blood vessels to dilate.

Studies have also shown that magnesium depletion seems to help release serotonin from its storage sites. It also helps make blood vessels in the brain more receptive to serotonin and thus clears the way for serotonin to cause constriction of blood vessels.

Replacing magnesium has been shown to have a very positive effect on migraine symptoms in some people.

So, it’s good to know the causes of your migraines (keep a migraine journal ! ), and find natural ways to deal with those issues. 

Making Migraines a Thing of the Past
Migraine and Headache Relief with Shiatsu


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Anonymous said...

Why would ginkgo biloba be recommended for migraine relief when it expands the blood vessels, and expansion of the vessels is what caused the migraine in the first place?

Anonymous said...

this article states that the constriction THEN dilation of blood vessels cause migraine. So is one to believe that keeping the blood vessels at a constant size would help avoid migraines?

Patrick Judge said...

anonymous said expansion of the vessels is what caused the migraine in the first place?

wrong, theres a constricted area that happens first, when that stops the theres a rush of chemicals in response to that area and other areas

its all explained in the first paragraph,