Rhizotomy

Last Jan. I had a tumor removed. Doctors were hopeful this would end my pain. However, no such luck. My neurosurgeon wants to try a rhizotomy. He says I'm an ideal candidate since the risks of this surgery are facial numbness, and I'm already completely numb. Looking for advice and/or knowledge.

If you are already completely numb, how come u feel the pain, can the neurosurgeon reason this?