Electromyogram (EMG)

The needle electromyogram (EMG) uses a very small, thin needle that is inserted into muscles of the limbs and torso. This needle functions like a recording antenna to evaluate the electrical activity within the muscle, which gives information about the muscle itself as well as the nerve that services that muscle. The electrical waveforms displayed on the electrodiagnostic instrument have characteristic appearances and sounds, which determine whether or not the nerves are functioning normally or whether there has been injury. The wave forms can also indicate whether the nerve injury is old or new or if the nerve injury is recovering, which helps with prognosis. The number of muscles studied with the EMG depends on the distribution of the abnormalities found.

Nerve Conduction Study (NCS)

The nerve conduction study (NCS) records how effectively electrical signals travel in nerves. A small shock is applied to a nerve and the electrical response is recorded from another location in that same nerve or from a muscle serviced by that nerve. The electrical recordings provide information about the health of the different parts of the nerve cells (neurons).

Several nerves are tested to allow for proper interpretation. When you prepare for your nerve conduction study it is important that you not apply skin cream the day of your NCS because doing so will make it very difficult for the recording electrodes to stick to your skin.