Nerve Block Injections & Insurance Denial

I've been dealing with severe and chronic migraines for about seven years (up until then, they were episodic). In the fall of 2013 I went to the Cleveland Clinic's IMATCH program and it helped significantly. I find that among other things, stress is a huge trigger and when I started a new job in 2015 - especially one that required a lot of computer work - my migraines became worse again. My neurologist and headache specialist devised a regime of Botox injections every 3 months and nerve block injections every two weeks. I also use Topamax as a preventive and sumatriptan injection as an abortive. This helped keep the migraines manageable. In the summer of 2016, my insurance company suddenly decided to stop covering the nerve block injections. Their reasoning was that they weren't a proven and effective treatment for migraines. I guess Botox is because it's FDA approved. I don't know what I'm going to do - this past week I had to deal with a 5-day status migrainous for which I needed a 3 day taper of steroids to break and I missed a day of work.

Has anyone had the experience of a treatment they were receiving suddenly being denied by their insurance company? Was anyone able to fight and get the treatment covered? Thanks.