Managing constant pain was described to me as being like keeping a bath warm. You can keep it warm by adding a bit of how water regularly. If you let it go cold, it needs a heap of hot water and its uncomfortable while the temperature settles. To take that metaphor to pain relief, it means keeping the pain relief up and not waiting until the pain returns at the end of the 4 hours. We use a baseline of paracetamol, titrated with various combinations of oxycontin etc. Hopefully none of this is new to you.

It may be related to the chemo particularly around the ears, but I'm inclined to think its more related to surgery. I don't have any direct experience of it other than dental surgery, but it seems like nerve pain to me. Neuralgia, neuritis, something like that. I don't think an MO is the right specialty for this, but a doctor would be the best person to answer that. Has the MO suggested referring to someone else?

Keep going with the massages. It prevents Lymphedema, opens a physical connection for your mother, and its something practical you can do to help her. I know its enormously difficult for you. If you can, try to focus on separating the pain from the distress of the pain. Remaining calm and positive will help you focus on the practicalities you need to carry on, and the benefits will flow on to your mother. God be with you both.