Ann Clin Neurophysiol.  2017 Jan;19(1):28-33. 10.14253/acn.2017.19.1.28.

Nerve length measurement method in a radial motor nerve conduction study

Affiliations
  • 1Department of Neurology, Korea University Anam Hospital, Korea University College of Medicine, Seoul, Korea. nukbj@korea.ac.kr
  • 2Brain Convergence Research Center, Korea University Anam Hospital, Seoul, Korea.

Abstract

BACKGROUND
Previous studies of radial nerve conduction study (NCS) did not present how to measure the length of the radial nerve across the elbow, and did not even mention how to manage the spiral course of the nerve. This study aimed to applicate the most reliable method to measure the length of the radial nerve during NCS.
METHODS
Three points (A, B, and C) were determined along the relatively straight course of the radial nerve. The distance was measured using three different methods: L1) straight distance corresponding to the A-C distance, L2) sum of the distances corresponding to the A-B-C distance, L3) based on the L2, but the elbow is flexed at a 45° angle. We compared the three methods of distance measurement and the calculated nerve conduction velocities (V1, V2, and V3) in normal healthy subjects.
RESULTS
19 normal participants were enrolled. The mean value for method L1, L2 and L3 were 22.5 ± 1.8 cm, 24.0 ± 2.1 cm, and 23.2 ± 2.1 cm (p < 0.001). Calculated conduction velocities using those distance measurement methods as follows (p < 0.001): V1 (60.9 ± 2.7 m/s), V2 (64.6 ± 3.3 m/s), and V3 (63.4 ± 3.9 m/s). V2 was significantly greater than V1 and V3 (p < 0.001, p = 0.010, respectively).
CONCLUSIONS
The distance measurement using a stopover point near the lateral epicondyle between two stimulus points in position of a fully extended elbow with forearm pronation is the most appropriate posture for radial motor NCS.

Keyword

Radial nerve; Nerve conduction study; Length measurement; Conduction velocity

MeSH Terms

Elbow
Forearm
Healthy Volunteers
Methods*
Neural Conduction*
Posture
Pronation
Radial Nerve

Figure

  • Fig. 1. Illustration of the measurement of L1, L2, and L3. (A) Measurement L1 based on the A-C distance represents a linear measurement between the proximal and distal stimulation point. The elbow is extended fully. (B) Measurement L2 based on the A-B-C distance has a segmented course as contrasted to the single segment of L1. Point B is added on the elbow crease between the biceps brachii tendon and the lateral epicondyle. The elbow angle is the same as that of L1. (C) Measurement L3 is also based on the A-B-C distance, but the elbow is flexed at a 45° angle.


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