My husband has severe back pain and had an mri done which shows nothing wrong. why is pain mgmt sending him for nerve testing and what is happening?

Guessing that: Doctor is evaluating peripheral sciatica or a pyriformis syndrome and could tie together the diagnosis

EMG/NCS: can be very helpful in determining issues that may still be from the spine if MRI is not that conclusive. Also it could be a peripheral nerve injury or neuropathy that could cause his pain and the EMG will be helpful in determining this.