Electrodiagnostic Testing

Concord Orthopaedics offers electrodiagnostic testing, including electromyography (EMG) and nerve conduction study (NCS). Both of these diagnostic testing procedures test the electrical activity of muscles and nerves.


An electromyogram is a test of muscle. It is performed with a fine gauge needle electrode which is placed in the muscle. Several aspects of the muscle's function are tested. First, the muscle is tested at "rest". The patient holds the muscle still and relaxed while the needle is gently moved in the muscle. Next, the muscle is tested while it is contracting, first slightly, then maximally. Different aspects of muscle function are recorded. The muscle is not stimulated. All the measured electrical activity is generated by the muscle itself. An audio and visual signal is created and the patient will hear the audio signal generated by the muscle from the computer. The sound of each signal gives the physician important information about that muscle.


A nerve conduction study is a test designed to measure the function of a nerve. There are three major types of nerves: motor, sensory, and autonomic. Motor nerves carry information from the spinal cord to the muscle. Sensory nerves carry information from a sensory organ such as the skin or the eye to the spinal cord or brainstem. Autonomic nerves carry information from the spinal cord to an internal organ such as the heart, a blood vessel, or a sweat gland. Nerves are also described based on size and amount of insulation. Fast conducting fibers tend to be large and heavily insulated by a fatty material called "myelin". Slow conducting fibers tend to be narrow and minimally insulated.

Routine nerve conduction studies test large diameter motor and sensory fibers only. There are no well standardized tests, at this time, for smaller diameter fibers such as autonomic fibers and "c-fibers", which are the most important fibers for pain and temperature sensation.


EMG/NCS studies are generally used for any injury to peripheral nerves, such as:

  • pinched/stretched nerves (carpal tunnel syndrome, brachial plexopathy, cubital tunnel syndrome, cervical and lumbar radiculopathy, etc)
  • muscle diseases (myopathies, dystrophies), metabolic nerve diseases (neuropathy, amyotrophy), and motor neuron conditions of spinal origin (ALS, Guillain-Barre, etc).

EMG or NCS are not generally useful for spinal injury (spinal cord trauma, syrinx, multiple sclerosis) or brain injury (stroke, head injury, Parkinson's disease, etc.).

NCS is almost always a part of the study. Depending on the condition to be tested for, the EMG may or may not be included.

Click here to find out how an EMG or NCS is performed.

Click here to find out how to prepare for your EMG/NCS.