Damn, Don, I'm really sorry to hear this. I know how much Dizzy meant to you, and though we never got to meet, I know how great any of the Greyhound derivatives are as companions. Gentle, sweet, and very sensitive to their humans.
If you recall, Shug, my adotpted Greyhound, went through a similar decline. Suddenly, and nobody ever figured out what was wrong with him.
Dizzy...rest in peace.
I did a lot of homework the last 2 1/2 months trying to figure out what was going on when the local vets or regional specialists couldn't nail it down. Was weird that her first day she went from seeming entirely normal to being almost totally down in a span of 12 hours.
Prior to that I'd noticed very light tremors in her jowels over the prior couple days. Mine, then the vet's, first thought was these were petite mal seizures. Either some developed epilipsy on its own or brought along consequent to a stroke or brain tumor. Anti-seizure meds made no difference though. Different meds were tried. Closer and extended observation made me believe it wasn't seizures though. Have dealt with that before and this just wasn't quite that.
The vet then thought it was the activation of some long simmering tick borne illness. There are several. No definitive results from any tests to support this. Diagnosis was entirely inferential.
Diz just kept getting weaker and weaker though. Pronounced lack of signs of pain or other discomfort seemed odd (at least to me). Though she looked like a people might in the throes of a significant MS episode. Vets kept saying there's no canine analog though. So what do I know....
More blood tests than seemed fair and a host of other things checked for over the three months never produced any definitive answer. No course of meds ever made any change at all. As I kept digging I think she developed a slightly atypical (because of the sudden nature of the presentation, even though it could have been brewing for a long time) case of either degenerative myelopathy (
http://en.wikipedia.org/wiki/Canine_degenerative_myelopathy ) Depending on sources this is the same thing or something very similar to canine degenerative neuropathy.
Of everything I could find the pathogenesis of the disease states track with Dizzy's decline and presentation even including the lack of pain. Without a necropsy won't ever know for sure. And it won't have made a bit of difference as there is no treatment. This is what I think got her though.
I remember when your big Greyhound got sick Terry. Thought about that more than once during Dizzy's illness. Glad they're both through their tough times but wish it hadn't happened to them.