Nerve length measurement method in a radial motor nerve conduction study

Jae-Gyum Kim; Yoohwan Kim; Hung Youl Seok; Byung-Jo Kim

doi:10.14253/acn.2017.19.1.28

Journal List > Ann Clin Neurophysiol > v.19(1) > 1099497

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Kim, Kim, Seok, and Kim: Nerve length measurement method in a radial motor nerve conduction study

Original Article

Ann Clin Neurophysiol 2017;19(1):28-33.

Published online: 5 January 2017

DOI: https://doi.org/10.14253/acn.2017.19.1.28

Nerve length measurement method in a radial motor nerve conduction study

Jae-Gyum Kim¹, Yoohwan Kim¹, Hung Youl Seok¹, Byung-Jo Kim^1,²

¹Department of Neurology, Korea University Anam Hospital, Korea University College of Medicine, Seoul, Korea

²Brain Convergence Research Center, Korea University Anam Hospital, Seoul, Korea

Correspondence to Byung-Jo Kim Department of Neurology, Korea University Anam Hospital, Korea University College of Medicine, 73 Inchon-ro, Seongbuk-gu, Seoul 02841, Korea Tel: +82-2-920-6619 Fax: +82-2-925-2472 E-mail: nukbj@korea.ac.kr

Received 11 August 201616 November 2016 Accepted 21 November 2016

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

초록

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.

Keywords: Radial nerve, Nerve conduction study, Length measurement, Conduction velocity

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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.

Table 1.

Summary of previous radial nerve motor conduction studies involving a segment across the elbow

Author	Age range of subjects (mean age)	Stimulation site	Recording muscle	Measurement tool	Velocity
Jebsen et al.¹⁰	14-62 years (33 years)	(1) 3-4 cm proximal to the needle; (2) 5-6 cm proximal to the LE, groove between the BC and BR	EI	Not mentioned	58.4 ± 6.7 m/s
Trojaborg and Sindrup¹⁶	16-28 years (not mentioned)	-(1) 8 cm proximal to ulnar styloid; (2) 6 cm proximal to the LE, between the BR and BB	EI (TB, BR, EDC, EPL)	Obstetric caliper	62 ± 5.1 m/s
Humphries and Currier¹⁴	20-30 years (22 years)	(1) lateral surface of the brachium 6 to 10 cm proximal to the LE; (2) middle third of the forearm between the BR and extensor	APL, EPB	Steel tape measure	69.8 ± 12.90 m/s
Ma and Liveson¹⁷	Not mentioned	(1) forearm (several centimeters proximal to the recording electrodes); (2) Lateral brachium (6-10 cm proximal to the LE)	EI	Not mentioned	62.3 ± 6.4 m/s
Date et al.¹⁵	27-52 years (36.4 years)	(1) 8 cm proximal to the recording site; (2) 8-10 cm proximal to the LE, over the radial groove	EI	Flexible tape measure (across the antecubital fossa, just lateral to the BB tendon)	71.7 ± 4.7 m/s

LE, lateral epicondyle of the humerus; BC, brachialis; BR, brachioradialis; EI, extensor indicis; BB, biceps brachii; TB, triceps brachii; EDC, extensor digitorum communis; EPL, extensor pollicis longus; APL, abductor pollicis longus; EPB, extensor pollicis brevis.

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