Well trying not to court controversy but I’m pretty convinced MAV involves the inner ear. The inner ear itself might have had an upset (e.g. in the case of trauma) or its something to do with one of the processes that influences the inner ear, including but not limited to arterial pressure, CPP etc. These drugs may be reducing pressure on the inner ear and that is why you see a reduction of symptoms. In addition, if the ear is even mildly hydropic (for whatever reason), it probably responds to these changes even more than an ear in a healthy state would (due to blood barrier permeability being higher in a ear that is at higher pressure).
In this situation, the electrical, sensory response of the ear changes more in response to fluctuations in external bodily functions because it is more ‘hooked up to’/influenced by them. That might cause secondary neurological issues as the brain tries to cope with the changing response of the ear. We can’t ‘hear’ the vestibular sense but if we could we might notice a change in characteristics over time. It’s this noise the brain has to deal with, adapt to, but initially the brain gets extremely confused and this puts it under so much stress it heads into migraine state.
This represents a benign, reversible situation but simply a situation where the ear is sending more unpredictable signals to the brain. The brain is very sophisticated though and over time, within a certain threshold, the brain may be able to work around the noise.
There are so many variables though!
There … said it.