Visualization of radial nerve activity at the upper arm using magnetoneurography

Objective: To evaluate the function of the radial nerve in the upper arm using Magnetoneurography (MNG).

Methods: Eight asymptomatic male volunteers (age 25-63 years) and one 67-year-old female patient with radial nerve palsy were included. The radial nerve was electrically stimulated in the right wrist, and the evoked magnetic field was recorded using a 132-channel bio-magnetometer system with a superconducting quantum interference device positioned below the upper arm. The measurements were divided into distal and proximal sessions because of the extensive range of the nerve.

Results: MNG recorded the radial nerve's evoked magnetic field in all cases, and the neural activity of the radial nerve at the upper arm was visualized using reconstructed currents. The mean conduction velocity calculated from the peak latency of the inward currents was 43.9 m/s for distal measurements and 57.9 m/s for proximal measurements. A 67-year-old female patient with radial nerve palsy had a disappearance of the reconstructed inward current and conduction disturbance of the axonal current, facilitating the identification of the lesion site.

Conclusions: MNG allowed visualization of the radial nerve activity in the upper arm and facilitated the identification of the lesion site in a patient with radial nerve palsy.

Significance: This method could be a useful diagnostic tool for patients with radial nerve palsy.