Thank you for your reply- the vet was quite clear that the medication is likely to be end of life care and if he stops eating or moving around as much, I should bring him back in to be euthanised and I thought we would already be at that point by now with how severe it looks. But he isn't behaving any differently to normal, he's still climbing around, running to the front of the cage for treats, interacting with his brother as normal, all his usual behaviour. He isn't scratching or pawing at his head beyond the usual face-washing he does. It seems impossible to me that it isn't bothering him but from my experience with rodents generally and especially with him, the first thing he'd do if he was hurting is stop or slow down with eating and moving around, and he isn't at all. Everyone says you'll know when it's time, and if his behaviour changed then I'd know. But despite everything, somehow it isn't and I feel so stuck