Ann Rehabil Med.  2017 Apr;41(2):290-298. 10.5535/arm.2017.41.2.290.

Optimal Radial Motor Nerve Conduction Study Using Ultrasound in Healthy Adults

• Yeo J
• Kim Y
• Kim S
• Oh K
• Kang H

• KMID: 2389488
• DOI: http://doi.org/10.5535/arm.2017.41.2.290

Abstract

OBJECTIVE
To obtain reference values, to suggest optimal recording and stimulation site for radial motor nerve conduction study (RmNCS), and to analyze the correlation among RmNCS parameters, demographics and ultrasonography (US) findings.
METHODS
A total of 55 volunteers participated in this study. We hypothesized that "˜lateral edge of spiral groove (A)' was the optimal stimulation site, and the "˜largest cross-sectional area (CSA) of extensor indicis proprius (EIP) muscle (B)' was the optimal recording site. The surface distance between "˜A' and the lateral epicondyle of the humerus divided by upper arm length, was named the spiral groove ratio. The surface distance between "˜B' and the ulnar styloid process divided by forearm length, was named the EIP ratio. Using US, we identified these sites, and further conducted RmNCS.
RESULTS
Data was collected from 100 arms of the 55 volunteers. Mean amplitude and latency were 5.7±1.1 mV and 5.7±0.5 ms, respectively, at the spiral groove, and velocity between elbow and spiral groove was 73.7±7.0 m/s. RmNCS parameters correlated significantly with height, weight, arm length, and CSA of the EIP muscle. Spiral groove ratio and EIP ratio were 0.338±0.03 and 0.201±0.03, respectively; both values were almost the same, regardless of age, sex and handedness.
CONCLUSION
We established a reference value and standardized method of RmNCS using US. Optimal RmNCS can be conducted by placing the recording electrode 20% (about one-fifth) of forearm length from the ulnar styloid process, and stimulating at 34% (about one-third) of the humeral length from the lateral epicondyle.

Keyword

Ultrasonography; Electromyography; Radial nerve

MeSH Terms

Adult*
Arm
Demography
Elbow
Electrodes
Electromyography
Forearm
Functional Laterality
Humans
Humerus
Methods
Neural Conduction*
Radial Nerve
Reference Values
Ultrasonography*
Volunteers

Figure

• 

  Fig. 1 Ultrasonographic evaluation of radial nerve at the spiral groove. (A) The probe was placed along the straight line between lateral epicondyle of humerus and most lateral point of acromion process of scapula. The probe was then tracked in the proximal and distal directions, until the radial nerve was located at its most superficial level above the humerus. (B) Ultrasonographic evaluation of radial nerve which placed most superficially between TB and BR at the lateral edge of spiral groove (arrow, radial nerve with brachial artery). H, humerus; TB, triceps brachii; BR, brachialis.

• 

  Fig. 2 Ultrasonographic evaluation of EIP muscle. (A) The probe was placed along the straight line between styloid process of ulna and lateral epicondyle of humerus. The probe was then tracked in the proximal and distal direction to find the thickest site of EIP muscle. On the basis of that site, the largest cross-sectional area (CSA) of EIP muscle was measured. To reduce error, CSA was measured twice, and the average value was calculated. (B) Ultrasonographic evaluation of EIP muscle to find largest CSA site (dotted line, CSA of EIP). EIP, extensor indicis proprius; U, ulna.

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