What Causes Severe Leg Pain Along With Numbness On The Thumb?

My mother is suffering from sever pain in her feet accompanied by burning sensation near the thumb. She also gets frequent cramps in her leg. The orthopedic we consulted diagnosed it as sciatica pain and has prescribed Neucobal G-300mg and Levocarnitine tab.-500mg. I not convinced with the treatment given. Kindly help.