I wonder about endothelial dysfunction in relation to the dizziness that some patients experience. I know most patients with dizziness report it in conjunction with OI and low blood pressure, but, for the first several years of ME, my dizziness was constant regardless of position. I could be lying in bed and still feel a rocking motion.
The degree of my impairment was objectively confirmed at an otological center, but its cause was undetermined. I was told, however, that they sometimes saw this kind of dizziness in patients with "vascular insufficiency to the balance center of the inner ear." They suggested that I try niacin to dilate the tiny blood vessels of the inner ear.
Unfortunately, niacin didn't help me at all - although it did give me severe flushing more often than not.
Anyway, I wonder if endothelial dysfunction could explain some of the dizziness seen in ME/CFS. My doctors suspected that the blood vessels of my inner ear were constricted 30+ years ago. Even in patients who link their dizziness to low blood pressure, I'd imagine that "vascular insufficiency" in the inner ear could make them even more than usually sensitive to changes in blood pressure.