Emsy and Kurry,
I used to own (or be owned by) a cat who in the end had the same problem...Plus he would sh!t everywhere in the house (I even banned him from sleeping on my bed for that reason) - plus he was an epileptic too (nothing wrong with being owned buy an epileptic cat).
He ended up being put down at one of the local vet surgeries who a few days later sent us a really cute sympathy card (I wish I still had it too).
I was in tears for days.
I later found out that when Taffy (that was his name) was on the table to be euthanased, he just lied there, licked his nose and knew it was time to go to Kitty Heaven.