ladybirder...thank you for your full and informative and helpful reply, i fear that my answer may not be so helpful.
Steroids first: the response or lack of will depend upon the condition for which they are prescribed, but i intend to confine my answer to your particular problem.
" Two years ago he came to me and a sweeter more loving cat you couldn't find. But he was never able to groom his righthand side no matter how hard he tried. "
That is the key sentence to your post, indicating that we are not dealing with a recent neurological condition, although there might well have been an added recent event.The results of steroids, if at all would be dependent upon them being prescribed within 48 hours.....which clearly isn't the case here unless we are postulating a new incident. I don't like "new incidents" I prefer to tie all the symptoms into one diagnosis.
Only an MRI scan could determine the cause of your cat's long and persisting brain problem and I would presume that the steroids were given as a hopeful prophylactic measure rather than a therapeutic procedure and hence their effect will not be clearly seen, if at all.
As you know i am not a vet, but the picture is not one of a brain hemorrhage,but I stand to be corrected by experts in that field.
You have a cat with a long standing neurological disorder, now cannot stand and may be blind.....eating poorly...and a poor standard of life.