Related Experiment Video
Updated: Apr 3, 2026
Screening of Axonal Degeneration in Carpal Tunnel Syndrome Using Ultrasonography and Nerve Conduction Studies
Published on: January 11, 2019
Identification of optimal site of G1 placement for median orthodromic palmar nerve conduction study
Irisa M Devine1, Devon I Rubin1
1Department of Neurology, Mayo Clinic, 4500 San Pablo Road, Jacksonville, Florida, 32224, USA.
Introduction:
G1 electrode placement at the distal wrist crease during the median orthodromic palmar nerve conduction study (NCS) could result in a false negative study if compression is more proximal.
Methods:
In this study we aimed to determine the effect of median G1 electrode placement on distal latencies and amplitudes. Methods Median orthodromic palmar NCS was performed with the G1 electrode at the wrist crease and 2 cm proximal, stimulating 8 cm distal to G1. The difference in the distal latencies and amplitudes between the 2 recording sites was calculated.
Results:
In 26 controls and 25 carpal tunnel syndrome (CTS) patients, the mean proximal-distal latency difference and percent amplitude decrease (distal vs. proximal) was -0.085 ms/53% (controls) and -0.072 ms/45% (CTS).
Conclusion:
Distal latency is not significantly affected by G1 placement in the median orthodromic palmar NCS, but the amplitudes are nearly twice as high when G1 is placed 2 cm proximal to the wrist crease.
More Related Videos
Related Concept Videos
01:11Pulse Assessment Sites
01:22Spinal Nerves: Plexus I
The Cervical Plexus
The cervical plexus, formed by the anterior rami of the first four...
01:27Assessment of the Cardiovascular System III: Palpation
Jugular Venous Pressure (JVP) Measurement
Position the patient at a thirty- to forty-five-degree angle or in a semi-fowler's position. Look for the highest point of pulsation in the internal jugular vein and measure the vertical distance to the angle of Loius or sternal angle. A normal JVP is 3-4 cm above...
01:11Assessment of radial pulse
The radial pulse, located at the wrist, is often the preferred site for assessing peripheral pulse because of its accessibility and dependability. The process of determining the radial pulse involves several steps:
01:25Assessment of apical radial pulse
The A-R pulse assessment involves simultaneous evaluation of the apical and radial pulses. When the apical and radial pulse rates vary, this assessment helps identify a pulse deficit.
Pre-Procedural Preparation