Median Sensory Nerve - Recording the thumb (antidromic)

Last updated on Tuesday, October 6 2009 by blondarb

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

Recording Site: Thumb

Reference Site: Thumb

Ground: Palm or top of hand

Stimulation Site: Wrist

Procedure: The recording electrode is placed on the proximal phalanx of the thumb. The reference electrode is placed on the distal phalanx of the thumb. A distance of 10 cm is measured from G1 to the distal wrist crease between the flexor carpi radialis and palmaris longus tendons and then extended an additional 3 cm by drawing a straight line along the course of the median nerve. Stimulation occurs at the 13 cm wrist site. 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 should be placed over the wrist site, with the recording electrode distal. The finger electrodes should be connected to the stimulator with the former “G1” electrode acting as the cathode and the former “G2” electrode acting as the anode.

Useful for studying: Median nerve lesions, including CTS. 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 videos:

Digit 1 median-radial comparison study
A video showing the technique for the digit 1 median-radial sensory comparison study.

Related images:

Median Sensory Nerve – thumb (antidromic
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

Median Sensory Nerve Conduction Study - Recording the thumb (antidromic)
This photograph illustrates the technique for the median sensory study, recording from digit 1 (thumb). Sensation to digit 1, in most people, is split between the median and radial nerves, making this useful in a comparison study looking for a median mononeuropathy at the wrist (carpal tunnel syndrome).

For Comparison, Radial Sensory Nerve Conduction Study - Recording the thumb (antidromic)
Shown for comparison, this photograph illustrates the technique for the radial sensory study, recording from digit 1 (thumb). Sensation to digit 1, in most people, is split between the median and radial nerves, making this useful in a comparison study looking...