What Causes Tremors In The Body After A Spinal Fracture?

My mother who is 81 years old had surgery to remove a benign tumor over 40years ago. Her pituitary gland was removed and she has been on the following medications: Cortisone, Synthroid, DDAVP and Phenobarbital. She recently fell and fractured her spine. After that she has been having hand tremors and feeling weak, and a loss of appetite , probably due to the pain medications she was on oxycodone etc. she has seen a neurologist and MIR brain scans show no sign of tumor present nor do they think it is parkinsons. My question what is causing the hand shaking. She has been seeing an endocrinologist since the surgery who monitors her blood work every 6 months. Thank you, Dominick