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.