@GriffinsMom, my girl Lady had a suspected brain tumour when she had a seizure at 13 years of age. My vet put her on Prednisone, and things improved. She was on and off the drug for the next few years until she really started to get worse at just short of 16 years old. My vet said that for some, Prednisone seems to shrink the tumour. Of course, it would depend on size and location. I don't want to give false hope, but you might inquire about it.
