Avoiding false-negative nerve conduction study in ulnar neuropathy at the elbow

Ulnar nerve displacement at the elbow causes overestimation of nerve conduction velocity. We hypothesized that this overestimation may cause false-negative results when the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM) diagnostic criteria are used.

We investigated 9 cases of ulnar neuropathy at the elbow, all having ulnar nerve displacement confirmed by ultrasonography and meeting none or just one of the AANEM criteria with distance measurement by anatomic landmarks. First, the distance across the elbow segment was measured by anatomic landmarks, and then it was re-estimated by ultrasonography.

Overestimated ulnar conduction velocity was corrected by 7.9 m/s. Three cases met none of the AANEM criteria before correction. After correction of overestimation, all cases met two of the AANEM criteria.

This study highlights the importance of using ultrasonography to confirm the possibility of ulnar nerve displacement, especially when electrodiagnostic findings do not meet AANEM criteria in patients with suspected UNE.