Origin:  C8-T1 roots, lower trunk and medial cord of the brachial plexus, median nerve.

Recording Site:  Abductor Pollicis Brevis muscle (APB)

Reference Site:  Base of thumb

Ground:  Palm or top of hand

Stimulation Sites:  Wrist and elbow

Procedure:  The recording electrode is placed over the belly of the APB. The reference electrode is placed at the proximal phalanx of the thumb.  Stimulation occurs at the wrist, above the distal wrist crease and at the elbow, just above the elbow crease, medial to the pulse or the biceps tendon.  The distance between G1 and the distal stimulating site at the wrist is 4-6 cm.  Additional stimulation sites include the axilla and Erb’s Point.