I've had migraines for four years and ringing in my ears (tinnitus)for over two of those. It is constant; less when the headache's gone away for a spell, extrmely loud at the onset of migraine and ususally lasting throughout the episode.
An ENT performed an extensive battery of tests, and he diagnosed it as basal arterial migraine. He says the cure is worse than the symtom, so don't even try. I didn't pursue the issue and have just put up with the noise.
I've been on Topomax before, and it really had neither a positive or negative effect on the ringing.
Sometimes I think the local fire department will be rushing to their cars and off to the station in response to the ringing and am incredulous that none of my family can hear it. They politely smile and nod.
I freuqently have to sleep on the couch with the TV blaring just to get to sleep, the ringing becomes the focus of my attention and prohibits merely "dropping off'" into dreamland.
Of all the things that could befall me, I feel this is one I can live with relatively easily...one does become accustomed to it after a while, trust me.
Try the Tinnitus Association for more info
Keep the faith