I developed severe migraines about the same time my SD kicked in - but I didn't know it was SD at the time. I attributed my voice and migraine problems to stress and overuse of my voice. My neurologist who treats me for migraines had never heard of SD, but once I discovered what I had and began botox treatments, I brought her up to speed. Recently, she suggested botox for my migraines. I agreed since the botox for my voice was so successful.
I have to say, the botox is working very well! She injected 19 sites around my forehead, temples, jaw, neck and shoulders. Of course I also have to say that I am virtually wrinkle free - a wonderful side benefit!
But to answer your question - I don't think the botox for migraines helped my voice - just as the botox for SD didn't relieve my migraines or wrinkles! But we just started, so time will tell.