A few evenings ago, I got up from my bed and the room swirled around me so violently that I had to grab a chair to prevent myself from falling over. The next morning and following few days showed no improvement, so I asked a friend to drive me to the doctor.
After taking my blood pressure, the doctor held my head in his hands and performed a few brusque manoevres, pushing me onto the bed on the right, lifting me upright, then throwing me to the left, pausing to peer intently into my eyes between moves. He then sent me home and said that I was OK, but that if the effects continued another few days that he would send me to an ear/nose/throat specialist.
Mystified I came home and did some research on the Internet. I had Benign Paroxysmal Positional Vertigo (BPPV), an inner ear disorder caused by calcium crystals, or ear rocks, floating into areas that interfere with one's sense of equilibrium. YouTube had some short videos on the Epley Manoevre, which should set me right after a few days. Whew.
Keep this mind if you have this experience. It's not necessarily the dreaded brain t–––r.