Origin:  C6-C7 roots, upper and middle trunk and lateral cord of the brachial plexus, median nerve

Recording Site:  Index finger

Reference Site:  Index finger

Ground:  Palm or top of hand

Stimulation Site:  Wrist

Procedure:  The recording electrode is placed on the proximal phalanx of the index finger.  The reference electrode is placed on the middle phalanx of the index finger.  A distance of 13 cm is measured from G1 to the distal wrist crease over the median nerve.  The nerve is stimulated at the wrist, proximal to the wrist crease and between the flexor carpi radialis and palmaris longus tendons.  The nerve can also be stimulated at the elbow (above the elbow crease, medial to the brachial artery pulse or biceps tendon).

This study can also be performed orthodromically.  A bar electrode is placed over the wrist site, with the recording electrode distal.  The finger electrodes is connected to the stimulator with the former “G1” electrode acting as the cathode and the former “G2” electrode acting as the anode.