Have you lot tried migraine meds? Most people think "migraine = headache" which is WRONG, very wrong. You can in fact have CONSTANT dizziness (no spells or attacks whatsoever), without ever having a headache, and it could still be migraines. On the other side, you can have pretty much any kind of vertigo or dizziness, including (BADLY in my case) visual vertigo, i.e. feeling motion sick from watching ANY motion. I do mean ANY, I can't even WALK without feeling ill.
Here's a forum about MAV (Migraine Associated Vertigo):
http://www.mvertigo.org/ (seems to be down right now, hopefully temporarily!)
More info about MAV:
http://www.emedicine.com/ent/topic727.htm
Now, there are misconceptions about MAV, too. Here are a few quick facts:
* You can have spells/attacks, with true vertigo, and/or *constant* dizziness for months or YEARS. Some pages only talk about shorter attacks (hours to at most days), and only true spinning vertigo, which is not the case.
* You do NOT need to have headaches to qualify (migraine is a neurological disease; blood vessel problems cause the symptoms, and headache is only ONE symptom). In other words, if you're having undiagnosed dizziness, PLEASE check out migraines. I was very sceptical at first but now, after taking to diagnosed people and an expert on the subject, I'm 99% sure MAV is what I have.
If you've ruled out most other things, please look into MAV - it's becoming increasingly more "popular" as a diagnosis as doctors are learning about it.
Best docs to see would (in order) be a neuro-otologist, or a neurologist followed by ENTs, I'd think. Neuro-otologists are the best in this area, for sure.
Regular migraine medicines are used (it's after all a regular migraine, despite what people think about migraines).
Pizotifen, verapamil, topamax, depakote are a few examples of prophylactic drugs (= preventive meds).
In any case, good luck! I've had this crap for 8 months and I can't imagine having anything like this for 12 years!