I Have Been To A Specialist For My Carpal Tunnel

I have been to a specialist for my carpal tunnel and had injections twice. They helped at first, but now the numbness has returned and I am also experiencing a throbbing pain in my right thumb (at the base). My hand hurts terribly when writing also. My doctor wants to schedule a myelogram, but I forgot to ask what is involved with this procedure. Can you tell me what to expect? Also, do you know how long the recovery time is for the surgery?

Thanks