Evaluation of the ulnar nerve with shear-wave elastography: a potential sonographic method for the diagnosis of ulnar neuropathy

Abstract

Purpose: This study was designed to verify whether shear-wave elastography (SWE) can be used to differentiate ulnar neuropathy at the cubital tunnel from asymptomatic ulnar nerve or medial epicondylitis. An additional aim was to determine a cut-off value to identify patients with ulnar neuropathy.

Methods: This study included 10 patients with ulnar neuropathy at the cubital tunnel as confirmed with electromyography (three women and seven men; mean age, 51.9 years), 10 patients with medial epicondylitis (nine women and one man; mean age, 56.1 years), and 37 patients with asymptomatic ulnar nerve and lateral epicondylitis (21 women and 16 men; mean age, 54.0 years). Each patient underwent SWE of the ulnar nerve at the cubital tunnel, distal upper arm, and proximal forearm.

Results: Patients with ulnar neuropathy at the cubital tunnel exhibited significantly greater mean ulnar nerve stiffness at the cubital tunnel (66.8 kPa) than controls with medial epicondylitis (21.2 kPa, P=0.015) or lateral epicondylitis (33.9 kPa, P=0.040). No significant differences were observed between patients and controls with regard to ulnar nerve stiffness at the distal upper arm or the proximal forearm. A stiffness of 31.0 kPa provided 100% specificity, 80.0% sensitivity, 100% positive predictive value, and 83.3% negative predictive value for the differentiation between ulnar neuropathy and medial epicondylitis.

Conclusion: Cubital tunnel syndrome is associated with a stiffer ulnar nerve than lateral or medial epicondylitis. SWE seems to be a new, reliable, and simple quantitative diagnostic technique to aid in the precise diagnosis of ulnar neuropathy at the cubital tunnel.

Keywords: Cubital tunnel syndrome; Medial epicondyle pain; Shear-wave elastography; Ulnar neuropathy.

Conflict of interest statement

This study was performed using a Samsung RS85 ultrasonography device demonstrated by DongKook Life Science. Co., Ltd., Republic of Korea.

Figures

Fig. 1.. A 58-year-old woman with right lateral epicondylitis.

Elastography images of the ulnar nerve at the elbow are shown. A. The shear-wave elastography (SWE) value of the ulnar nerve at the level of the distal upper arm was 7.2 kPa. B. The SWE value of the ulnar nerve at the level of the cubital tunnel was 15.6 kPa. C. The SWE value of the ulnar nerve at the level of the proximal forearm was 18.6 kPa. RMI, reliability measurement index.

Fig. 2.. A 68-year-old man with severe right ulnar neuropathy on electromyography.

Elastographic presentation of the ulnar nerve at the level of the cubital tunnel is shown. The shear-wave elastography value of the ulnar nerve at the cubital tunnel was high (160.2 kPa). RMI, reliability measurement index.

Fig. 3.. Receiver operating characteristic (ROC) curves for the diagnostic accuracy of shear-wave elastography (SWE) values for the ulnar nerve at the cubital tunnel (A), SWE ratios of cubital tunnel to proximal pressure (B) and cubital tunnel to distal pressure of the ulnar nerve (C) in the detection of ulnar neuropathy.

A. The area under the ROC curve (AUC) for the SWE value for the ulnar nerve at the cubital tunnel was 0.736 (95% confidence interval [CI], 0.560 to 0.912). B. The AUC value of the ratio of cubital tunnel to the proximal pressure of the ulnar nerve was 0.728 (95% CI, 0.551 to 0.904). C. The AUC value of the ratio of the cubital tunnel to the distal pressure of the ulnar nerve was 0.732 (95% CI, 0.555 to 0.909).