Ultrasound Evaluation of the Normal Ulnar Nerve in Guyon's Tunnel: Cross-sectional Area and Anthropometric Measurements

Abstract

Background: Ulnar nerve (UN) entrapment is an infrequent disorder, but is often seen in long-distance cyclists. Electrodiagnosis and imaging modalities, including ultrasound, are used for diagnosis. The goal of this study was to obtain sonographic normative data of the UN in Guyon's tunnel, to establish the diagnosis of Guyon's tunnel syndrome in future studies. Anthropometric measures were also obtained. Methods: A total of 46 healthy volunteers (30 men) were recruited (mean age, 24.7 ± 3.1 years), and a total of 83 wrists were examined. The examinations included anthropometric measurements (wrist width, wrist depth, wrist circumference, palm length, and hand width) and ultrasound measurement of the cross-sectional area (CSA) of the UN in Guyon's tunnel. B-mode sonography and power Doppler were employed. Results: The UN CSA in Guyon's tunnel for male volunteers was 6.0 ± 2.0 mm2, and 5.0 ± 1.0 mm2 for female volunteers. There was a significant difference between female and male volunteers in the measurements of wrist width, wrist depth, wrist circumference, palm length, hand width, and UN CSA (p < 0.001). The UN CSA was correlated with wrist width, wrist depth, wrist circumference, palm length and hand width (p < 0.01). Differences were noted within and between gender groups of UN CSA within Guyon's tunnel. Conclusion: Nerve CSA may differ by gender and this may be related to body size. Therefore, the contralateral side is more useful as a reference standard than the gender mean.