could someone explain to me why we get visual disturbance in migraine?

I have read about the different stages, but am not quite sure what is happening to our eyes and why, has anyone that has had acess to migraine aura books got a good explanation? The only one I found was in doctor speak and I havn't a clue what it was talking about.

regards

Di

it has to do with blood vessels narrowing and the created disturbances

http://headaches.about.com/od/migrainediseas1/a/aura_ache.htm

Risa

There was an excellent article in either Scientific American or Discover a few years ago about migraine auras. I get both mags and I can't remember which one it was in.

Here is a brief synopsis of what they found. THhy had a test subject who always got a migraine with excercise so they had him play basketball until he had an episode and then took a PET scan ( I think) and took pictures of his brain function during the aura stage. They found that his visual cortex developed a "dead" area that then spread like a wave through the visual cortex in the same pattern as his visual aura.

After about 20 minutes or so, the wave pattern reached the edge of the visual cortex and the aura disappated. Pretty wild. huh? The reason for the dead area and wave pattern all has to do with brain wave activity which is controlled by neurotransmitters. As your neurotransmitters stop working or decrease their function below your own brain's ability to function, by whatever mechanism, a part of your brain has a reaction which is just the start of the migraine episode.

So they concluded that the aura is a physical manifestation on decreased brain activity in that area. My conclusion is that depending on where in your brain the activity is being affected, you get some sort of aura whether visual, auditory, olfactory, taste, numbness, etc.

Now this is just a brief description of a pretty long article so any errors are mine. I will try to find the original article as it was really interesting and gave me a great insight into auras.

Alli

That was a good discription of why. I had not put a connection with Migraines and smell. I often smell things that are not there. One of the most disgusting smells is stale nicotene. I hate it when that one comes around. Would you believe that I can smell the cigar in the car behind me going down the highway at 70 mph with the windows closed?

Hal

GREAT explanation ... and that was a fascinating study. the guy who could bring on a migraine at will was a perfect test subject.

the way I understand migraine episode oddities (and wow do Iget all the oddities) is this. Imagine brain cell (neuron) A. It is right next to, tangled up with Neuron B, Neuron C, and lots of others. Neuron A wants to send a message to Neuron B. So Neuron A releases chemicals to communicate with Neuron B. but when we migraine, Neuron A's message ends up at Neuron C ... and all heck breaks out. We get sights and smells and sounds and confusion that others simply have to take hallucinogenic drugs to experience. But we get all this fun for free.

It is like Alice wants to send a secret email to Barbara. But the Internet goes screwy and Christine gets the email message instead of Barbara. Christine goes ballistic (the secret was about her). So she forwards the original email with a blistering response to Donna. However instead of Donna, Elizabeth gets the message. Now Elizabeth is best friends with Alice, so she gets ticked off and blasts off an email to Flora and Alice ... except Barbara and Georgene get the email. And so on and so on until the entire community is all in an uproar and saying and doing things they do not normally do!

That's the way I understand what is happening with aura's and other symptoms.

Great analogy Richard and thank you Allli. I always sort of wondered what went on...and explains the weird symptoms. I don't get a classic aura, but lately when an M is escalating I get double vision. I can force it to converge but the wiring keeps misfiring. I've also gotten dog hearing on occasion - I know why dogs howl at some things, ouch! And why it gets better/worse.

This isn't the article I was referring to, it is a later one but it includes the information from the first article.

http://en.wikipedia.org/wiki/Cortical_spreading_depression - go to the bottom of the page and click on the "why migraines Strike" and you can get to the article that way. The previous link required a subscription.

Here is a brief excerpt from the original article.

http://discovermagazine.com/2000/mar/featpain

I had my one and only migraine scotoma a few weeks ago. It filled my field-of-view and made me blind for 30 minutes or so.

What was really interesting was that even if I closed my eyes I still saw the scotoma. Also, I could not form an image in my imagination because the scotoma was there. From that I realized two things:

1) The scotoma was in some part of my visual cortex, not my eyes or optic nerves; and
2) You need your visual cortex to even imagine images.

I never knew either of these things before. Experimental science is cool.

That's a cool observation...I never knew that. It does make some sense though...

I am all for scientific experimentation but not sure I wanted to be the subject.

Thankyou for such a full explanation of what is going on. I also loved the analgy too that sound very much like my own sort of of understanding.

If it creates a dead space where stuff isn't happening is that why sometimes I don't notice things then they are suddenly there? like a car when I'm crossing the road if over tired? I know our eyes can continue using existing information so we think we can still see fine and only renew the new stuff, so if our migraine blocks out the new stuff for a bit it could be dangerous.

Makes me wonder how safe I am when I drag myself out of the house even on public transport.

Di

I love Richard's analogy. Almost gives me a migraine reading it.