Ultrasonographic Findings of the Normal Ulnar Nerve in Adults

Objective: To provide a detailed description of the ultrasonographic findings along the entire length of the normative ulnar nerve.

Design: Volunteers were recruited to undergo ultrasonography of both upper extremities. Age, sex, height, weight, body mass index, arm length, and hand length were recorded, and cross-sectional measurements of the ulnar nerve were obtained at 7 predetermined sites.

Setting: The diagnostic neurology laboratory of a referral medical center.

Participants: Thirty volunteers (60 arms) were recruited. Volunteers were screened by history and physical examination, and those with evidence of peripheral nervous system disease were excluded.

Interventions: Not applicable.

Main Outcome Measure: The average cross-sectional area (CSA) of the ulnar nerve at 7 predetermined sites along the entire course of the nerve.

Results: The following average ulnar nerve CSAs were obtained: distal wrist crease, 5.9 mm2; arterial split, 6.3 mm2; 2 cm distal to tip of the medial epicondyle, 6.4 mm2; tip of the medial epicondyle, 6.5 mm2; 2cm proximal to tip of the medial epicondyle, 6.7 mm2; mid-humerus, 6.1 mm2; and axilla, 6.2 mm2. There was no statistical difference in nerve size when dominant and nondominant arms were compared, but women did have smaller nerves than men. Of all the variables measured, nerve size correlated most closely with weight, with a correlation coefficient of .59.

Conclusions: The ulnar nerve was easily visualized and measured along its entire course, and the CSA of the nerve was consistent at multiple sites. The reference values obtained in this study will facilitate the analysis of abnormal nerve conditions, and the information on side-to-side variation and sex-specific differences should be particularly helpful.