"Vasovagal syncope is a common cause of dizziness, lightheadedness, and fainting. The vagus nerve is overstimulated and causes the body's blood vessels to dilate and the heart to slow down. This anti-adrenaline effect decreases the ability of the heart to pump blood upward to the brain. Without blood flow, the brain turns off. In Victorian England, when this happened because young ladies' sensibilities were easily offended, this was called a swoon."
From what I understand, irritation of the vagus nerve can cause fainting, which I have actually experienced pre-Nissen...I was eating at a restaurant and ended up fainting dead-away and my blood pressure wouldn't go back up, so I was transported to the ER...no decision regarding what happened.
I did have a time when my inner-ear was disturbed and I had a lot of dizziness and even walked crooked at times. You might check into that as well.
Good luck finding answers!