My Greyhound bitch suffered a massive fit/seizure 5 weeks ago and the vet said it was a miracle she survived, but fortunately she is now on the mend and would put her at 95% back to her old self. She is still on Antbiotics and Predisolene (steroids) and vet says we must be careful about how long she is on the steroids, and mentioned Cushings to me as a possible side effect of steroid medication, cannot be cured apparently but is controlable, sorry to hear about this and hope your dog is ok in the future.
Plenty of info, but found this link for you, hope this helps
www.2ndchance.info/cushings.htm