People are going to get REALLY BORED of me saying this, but IMHO, 24/7 chronic dizziness IS NOT caused by migraine. There is some absolutely counter-productive dogma in the medical community right now that this condition is caused by migraine. As far as I'm concerned it is ABSOLUTELY NOT.
There appears to be no proof either way, but far more compelling an explanation to me is that inner ear issues cause migraines and some people are more susceptible to migraines than others, but DON'T BLAME THE BRAIN, a migraine is almost certainly a completely natural response to a mess of sensory signals that no longer make sense and confuse the brain.
I'm in a particularly interesting position because my 'MAV' came a few months after an initial 5 week spell of dizziness and imbalance caused by me pointing my shower into my ear. I am CONVINCED mine has a physical pathology and cause, yet I have all the same symptoms that make up MAV.
I think its FAR MORE likely that MAV is simply a form of inner ear 'upset' or 'injury' that isn't as extreme as, say Meniere's, but nonetheless causes enough upset to give the sufferer regular migraines. Even Dr. Hain documents that BPPV, fistula's and Menieres can give the sufferer migraines, so why not some other inner ear issue?
I'd go further and speculate that one day it may turn out that many migraine sufferers probably have some issue with their eyes or ears, however slight.
MRI scans are woefully inadequate to resolve the kind of detail we are talking about in the inner ear. They can rule out tumours on the nerve, but cannot resolve blood or air in the labyrinth, for example, both of which would probably upset the smooth working of the sense. A cone beam CT scan is probably better, but even then I don't think there has been any medical literature that sheds additional light on what's going on in the inner ear during dizziness and vertigo attacks. And lets not get started on how you accurately measure fluid pressure in the ear ...
The diet is still a good idea as it can decrease the chance of a migraine reaction to the sensory upset, and "migraine prophylaxis" with meds seems to dampen the dizziness feelings as well as the attacks.
Hope you feel better.