I'm doing this blog in a response to HunterRider4eva's question in my comments from my last blog entry.
Here is a link for a long winded version. Mine will be the short version!
My mare Squeaky was diagnosed a Roarer when she was younger around 5 years old. You see it in horses when they are put into work. She was taken to New Bolton to have the tie back surgery done. She also demolished the treadmill up there. I was not her owner at the time but they apparently put them on the treadmill to imitate being in work. She flipped out and busted out of it. This has led to a life long fear of loading and unloading on a straight load trailer. She will load like a pro on any side ramp trailer but ask her to load from the rear and its a fight not worth fighting.
She had the surgery but my guess is that it didn't tie it back all the way. I rode a showed her all through Pony Club from when she was about 9 to 13 then gave her away for a little while and got her back when she was about 16. She was always a little loud but when I got her back the second time it was worse. The lesson barn she was in used draw reins on everything... She just wants to put her nose to her chest and evade the bit. All that hard dressage work I had in her was gone. She just went around in this fake headset. I have tried many bits and exercises to get her back but the roaring is really noticeable when she goes in any sort of frame. If you let her keep her nose poked out as far as possible she doesn't roar as loud.
I don't really know what my plans are with her at this point. She is basically semi retired and we just do an occasional jot around the ring. If she was more fit she probably wouldn't make as much noise but it never did affect her performance. You just heard her coming! Hope the link above answers your question!