Ultrasound evaluation of ulnar neuropathy at the elbow: correlation with electrophysiological studies.

OBJECTIVES To evaluate, in patients with ulnar neuropathy at the elbow (UNE), if ultrasonographic differences in ulnar nerve size correlate with severity score determined by electrodiagnostic studies. METHODS We examined prospectively 38 patients (50 elbows) with UNE. Patients were classified into mild, moderate and severe groups according to electrodiagnostic studies. Cross-sectional areas (CSAs) of the ulnar nerve were measured 4 cm proximal to the medial epicondyle (CSA-prox), 4 cm distal to the epicondyle (CSA-dist) and at the maximum CSA (CSA-max) of the ulnar nerve found between these points. We used a control group of 50 normal elbows. RESULTS The CSA-max in the patient group was highly correlated with the severity score obtained by electrodiagnostic studies: mild: 11.1 +/- 3.4 mm(2), moderate: 15.8 +/- 3.8 mm(2), severe: 18.3 +/- 5.1 mm(2) (P < 0.001). Patients with UNE had larger ulnar nerve CSAs than controls at all three levels (P = 0.012 for CSA-prox, P < 0.001 for CSA-max, P = 0.003 for CSA-dist). A cut-off point of > or =10 mm(2) for CSA-max yields both sensitivity and specificity of 88%. CONCLUSIONS Ultrasonography can have a role not only in the diagnosis, but also in the severity stratification of patients with UNE.