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Ann Clin Neurophysiol > Volume 19(1); 2017 > Article
Ann Clin Neurophysiol. 2017; 19(1): 13-19.
Published online January 26, 2017.
doi: https://doi.org/10.14253/acn.2017.19.1.13
Median and ulnar F-wave inversion as a supplementary criterion for diagnosis of carpal tunnel syndrome
Yoohwan Kim1,*, Jae-Hong Jang1, Charles S. Cho2, and Byung-Jo Kim1,3* 
1Department of Neurology, Korea University Anam Hospital, Korea University College of Medicine, Seoul, Korea
2Department of Neurology, Stanford University School of Medicine, Palo Alto, CA, USA
3Brain Convergence Research Center, Korea University Anam Hospital, Seoul, Korea
Corresponding Author: Byung-Jo Kim ,Tel: +82-2-920-6619, Fax: +82-2-925-2472, Email: nukbj@korea.ac.kr
Received July 15, 2016   Revised: October 14, 2016    Accepted November 9, 2016
Copyright © 2017 The Korean Society of Clinical Neurophysiology
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.
Background: Median F-wave latencies are physiologically shorter than ulnar latencies, but they are often longer relative to ulnar latencies in carpal tunnel syndrome (CTS). This study aimed to investigate the value of absolute F-waves and relative latency changes compared to ulnar latencies in the diagnosis of CTS.
Methods: F-wave latencies of median and ulnar nerves in 339 hands from 339 patients with CTS and 60 hands from 60 control subjects were investigated. Mean F-wave minimal latencies of median and ulnar nerves were compared between groups. Patients were further divided into subgroups based on Canterbury grading and then analyzed using F-wave latency differences (FWLD) and F-wave ratio (FWR).
Results: Of 339 hands in the CTS group, 236 hands exhibited F-wave inversion based on the FWLD criterion and 277 hands had F-wave inversion based on the FWR criterion. F-wave inversion had a sensitivity of 81.7% using the FWR criterion to diagnose CTS. The mean FWLD and FWR were significantly greater in all patient subgroups compared to the control group (p < 0.001). In addition, mean FWLD and FWR showed significant correlations (r = –0.683 and r = 0.674, respectively, p < 0.001) with disease severity.
Conclusions: F-wave studies are effective supplementary diagnostic tools comparing to other standard electrophysiologic criteria for screening patients with CTS.
Key words: Carpal tunnel syndrome; Diagnosis; Electrodiagnosis; Sensitivity and specificity; F-wave
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