Where Does Ultrasound Fit in the Diagnostic Algorithm for Cubital Tunnel Syndrome?

Abstract

Background: Ultrasound (US) has emerged as a promising supplement to electrodiagnostic studies (EDX) in the diagnosis of cubital tunnel syndrome (CuTS) and has potential to be performed by novice operators. Our objective is to understand the discrepancies in assessment between the two modalities and to assess the utility of US in CuTS diagnosis by a novice operator. Methods: Patients who presented to a single tertiary academic medical center and clinically diagnosed with CuTS were prospectively enrolled. Electrodiagnostic studies were performed along with US measurements of the cross-sectional area (CSA) of the ulnar nerve by both a board-certified physiatrist and novice operator. Electrodiagnostic study and US outcomes were compared among four diagnostic impression groups: EDX–/US–, EDX+/US–, EDX–/US+, and EDX+/US+. Results: Sixteen patients were classified as abnormal by both EDX and US, 14 were classified abnormal by US only, 3 were classified abnormal by EDX only, and 6 were classified normal by both EDX and US ( P = .008, K = 0.14). The EDX+/US+ group had a significantly reduced sensory amplitude compared with the EDX–/US+ ( P = .04) group. Diagnostic classifications between a board-certified physiatrist and novice operator were in moderate agreement (K = 0.58, P = .08). Conclusions: Ultrasound detected a greater proportion of patients as abnormal than EDX. A subset of patients with clinical diagnoses of CuTS had normal sensory amplitudes but increased maximum nerve CSAs. Competency in US may be easily acquired with minimal training, suggesting its potential to be extended for use by other members of the health care team.