As you likely know already, there are a myriad of causes that manifest in migraine and vertigo. Makes for difficult diagnosis. A quick suggestion for you to try.
Type into your favorite search engine "ear crystals".
Obviously, I don't know if this will be relevant to your situation in any way or not, but it could spare you both a lot of time and undue suffering.
Ear crystals are well known in ear/nose/throat medical circles, but often ignored and left untreated. Shameful!