Neurophysiological Diagnostic Methods

Neurography and electromyography (EMG) are used to diagnose nerve damage and muscle disorders. Neurography tests nerve function using a weak electrical current—electrodes are placed on the skin, through which a small current is passed to stimulate the nerves, and a computer records how the signal travels along the nerve. You may feel slight pain or tingling during the test. A neurography test usually lasts 20 to 40 minutes.

An EMG test measures a muscle’s electrical activity at rest and during contraction. This test is always performed in conjunction with a neurography. A very thin needle electrode is inserted through the skin into the muscle to record the muscle’s electrical activity. An EMG combined with a neurography can take between 40 and 60 minutes.

Before the test, you must provide information about all medications and dietary supplements you are taking; you will be asked questions about allergies and blood clotting disorders. You must not have any extensive skin infections. Avoid exposure to cold before the test; it is recommended that you wash without using lotions or creams, and you must not smoke or consume caffeine for several hours before the test.

These tests are used to diagnose polyneuropathies (such as those associated with diabetes), compression neuropathies (carpal or cubital tunnel syndrome), nerve injuries, brachial plexus injuries, as well as muscle diseases—myopathies, neuromuscular transmission disorders, motor neuron diseases, ALS, post-polio syndrome, spinal muscular atrophy, and Bell’s palsy.