Shear-wave elastography in the diagnosis of ulnar tunnel syndrome.

Abstract

An interesting alternative to traditional diagnostic techniques of the upper extremity nerve entrapments might be an ultrasound elastography that has started to gain attention in recent research. The aim of this preliminary study was to verify whether a quantitative analysis of the ulnar nerve stiffness by shear-wave elastography can be used to diagnose ulnar tunnel syndrome (UTS), an ulnar nerve neuropathy at Guyon's canal. The study included 46 patients (39 women) and 39 healthy controls (34 women). All diagnoses in patients and controls were confirmed with nerve conduction studies. Measurements of nerve stiffness were taken at three levels: Guyon's canal (G), distal forearm (DF), and mid forearm (MF). Additionally, the ulnar nerve cross-sectional area at the canal's level was determined by ultrasonography. Patients with UTS presented with significantly greater nerve stiffness than the controls (mean, 99.41 kPa vs. 49.08 kPa, P < 0.001). No significant intergroup differences were found in the nerve elasticity at DF and MF levels (P < 0.836 and P < 0.881, respectively). An ulnar nerve stiffness value of 80 kPa and G:DF and G:MF ratios equal to 1.5 provided 100% sensitivity, specificity, and positive and negative predictive values in the detection of the syndrome. The mean nerve cross-sectional area in the Guyon's canal was significantly greater in patients than in the controls (4.63 mm², range, 2-7 mm² vs. 3.23 mm², range, 2-5 mm², P < 0.001). In conclusion, we believe that shear-wave elastography has the potential to become a useful adjunct diagnostic test for UTS.