Ultrasonographic Findings of the Ulnar Nerves in Cubital Tunnel Syndrome

ABSTRACT

PURPOSE: To determine useful diagnostic criteria of cubital tunnel syndrome (CTS), using ultrasonographic ulnar nerve cross-sectional areas (UNCSA) measurements. MATERIALS AND METHODS: The CTS group included 28 patients confirmed with nerve conduction study and the control group included 17 healthy adults. Ulnar nerve cross-sectional areas (UNCSA) were measured at the distal 1/3 upper arm level and in the cubital tunnel (CTN). US findings of CTS were ulnar nerve dislocation (n = 2), ulnar nerve subluxation (n = 5), ganglion (n = 1), sever elbow joint osteoarthritis (n = 1) and elbow joint valgus deformity after fracture (n = 1). UNCSA, the ratio of UNCSA in CTN to distal 1/3 upper arm level (CH ratio), and the difference of UNCSA between CTN and distal 1/3 upper arm level (CH difference) were evaluated to obtain the optimal diagnostic cutoff value of CTS, using ROC curve. RESULTS: The mean UNCSA in CTN was 0.168 cm2 in the CTS and 0.067 cm2 in the control. The CTS could be diagnosed when UNCSA, the CH ratio and the CH difference are larger than 0.096 cm2, 1.371 and 0.036 cm2 respectively. The ROC curve area was largest and the sensitivity, specificity was respectively 82.4%, 95.8%, when the CH difference was used as cutoff value. CONCLUSIONS: Ultrasound is useful for the detection of CTS pathogenic lesions in CTN. The highest diagnostic accuracy was acquired when the CH difference is larger than 0.036 cm2.