Hi Karen,
Being pretty OCD myself ;-), I surely understand your search for some definitive answers. However, I'm afraid that Cushing's is about as far as you can get from being a cookie-cutter type of disorder. It's labeled as being a "syndrome," meaning there's a whole big basket of *possible* symptoms or complications. But as far as predicting the actual road map for any individual dog -- that's pretty much impossible.
In my own personal opinion, probably the most difficult possibilities are these. First, for dogs suffering from pituitary tumors, I think the possibility of enlargement into macrotumors is one of the most unwanted outcomes. If the tumors enlarge enough, they can invade brain tissue and create neurological changes that can seriously jeopardize quality of life and even become life-threatening. As you probably know, that's what happened to my own Cushpup, Barkis. So I'm especially sensitive re: that risk. However, it's a minority of pituitary tumors that enlarge to that extent.
The development of the skin disorder, Calcinosis cutis, can also seriously affect quality of life. A couple of the other most serious complications from Cushing's would include high blood pressure (with the associated risk to vision, kidney function, etc.), and also an increased risk of creating/throwing blood clots. The article that I linked to in my previous reply noted that therapeutic trilostane treatment does appear to help lower liver enzymes and cholesterol levels, reduce proteinuria, normalize specific gravity of the urine, and ease calcinosis cutis. However, apparently it does not necessarily lower blood pressure or reduce the risk of clots. Whether or not Lysodren treatment is more successful in this regard, I do not know. But I'm thinking the general take-away is that some aspects of Cushing's indeed benefit from treatment, but some risks do remain since the disease is not actually curable. However, it is highly variable as to exactly how problematic those risks become for any given dog.
So I'm afraid I can't provide the specific roadmap that you're seeking. From my experience here throughout the years, every dog's path is different. Some take dramatic twists as did my Barkis. But for other dogs, Cushing's proceeds as more of a back-burner type of issue. Once the overt symptoms come under control, life goes on pretty much as normal and it may be some other unrelated health condition, or just old age, that ends up being the over-arching issue. In Annie's case, for instance, it may be the diabetes that provides more challenges than the Cushing's. So in honesty, I don't think there's any way to prepare in advance for what a new day may bring. The best any of us can do, whether dealing with Cushing's or not, is to rejoice in the good days, and then on the not-so-good days, bring any worrisome changes to the attention of our vets.
If you're born to worry -- like you and me -- Cushing's is just one more thing to worry about! I don't say that to be flip, but I've actually had just as much to worry about with my non-Cush dogs as I did with Barkis, and no better ability to predict what the next challenge was going to be. I would love to tell you what you can and cannot ignore, but in reality, worriers like us will never be able to ignore *anything.* The trick, I think, is just to go ahead and ask about anything that is bothering you, rather than fretting all alone and letting your worry overtake you.
I'm sure this was not the answer you were hoping for...but I'm trying to be as honest as I can. That's what we're here for, and we intend to stay right by your side ;-).
Marianne