I too had vertigo once, so bad I could not open my eyes without the room spinning so much I had immediate vomiting.. Wife too me to ER, also got meclizine as well as diazepam. Didn't help much. Got in to my primary care a few days later....in short, google the "Epley Maneuver". My primary did it to me and INSTANT relief. I had spent those few das gorked out on meclizine and valium for nothing. What happens when you get seen by a resident who doesn't have years of experience, or maybe isn't well read. I did a few visits of physical therapy to get my balance back but the vertigo was gone and never came back. This works for vertigo caused by the little bones in the semi-circular canals of the inner ear getting out of place. The maneuver sort of "swings" them back in place. I wouldn't wish it on my worst enemy (well maybe) but especially not to a fellow cyclist.
Hope this helps and you are better soon.