What is electromyography used for?

Nerve & muscle test. Electromyography (EMG) is typically performed along with nerve conduction studies. When performed by a skilled physician (who also does a history & physical exam), these tests can identify nerve & muscle conditions at any point in the 'circuit' from part of the spinal cord, nerve root (exiting your spinal column), through the plexus, peripheral nerve, neuromuscular junction, and muscle.
Electromyography. Is used to assess for nerve and muscle diseases. Typical symptoms evaluated for include: weakness, numbness, tingling. The test involves 2 parts, nerve conduction studies which involve surface electrodes and small electrical stimulations and electromyography/EMG which involves placing small needle electrodes into the muscles.