Can neurophathy emg test in lower back tell you if you have upper body or hand nerve damage as well?

No : An emg/ncv study of the lumbar spine is used to evaluate nerve issues related to the lower extremties and lumbar spine in order to evaluate the upper extremities or possible nerve issues in your hands or arms, you will need an emg/ncv of the upper extremities.

No: Emg of muscles in your low back and legs looks only at the lumbar roots, while nerve conduction studies (ncs) check nerves in your legs & feet. To check the cervical nerve roots in your neck you would need EMG of the muscles in your arms and hands, and possibly muscles in your neck. To check nerves in your arms and hands (carpal tunnel), you would need ncs of the arms and hands.