Median Sensory Nerve - Recording the index finger (antidromic)

Last updated on Tuesday, October 6 2009 by blondarb

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.

Usefule for studying: Median nerve lesions, including CTS. Upper, middle trunk and lateral cord brachial plexus lesions. Cervical radiculopathies.

Normal values *:

Amp: >15 uV

Distal Latency: <3.6 mSec

Conduction Velocity: >50 m/s

Temperature >32.0 C

Related images:

Median Sensory Study to Index
This cartoon shows the placement for the recording and stimulating electrodes for this study.

Deep anatomy of the right hand
This image shows the deep median and ulnar nerve anatomy of the hand

Superfical anatomy of the right hand.
This image shows the superficial nerves of the hand

Diagram of segmental distribution of the cutaneous nerves of the right upper extremity. Anterior view.
Diagram of segmental distribution of the cutaneous nerves of the right upper extremity. Anterior view. From Gray's anatomy.

Median Sensory Nerve Conduction Study, recording the index finger (antidromic)
This photograph illustrates the technique for performing a median sensory nerve conduction study, recording the index finger. The recording electrode (G1, black) is placed on the proximal phalanx of the index finger. The reference electrode (G2, red) is...