Abstract

OBJECTIVE:

To provide reference values and to compare this technique with the standard motor conduction velocity (MCV) of the ulnar nerve.

DESIGN:

Retrospective unmasked study.

SETTING:

Private and institutional practice.

PARTICIPANTS:

The reference group included 57 healthy volunteers. Patients included 100 subjects with suspected ulnar neuropathy at the elbow (UNE) referred for neurophysiologic evaluation. This group was subdivided into 2 groups: group A was composed of 45 patients with UNE confirmed by MCV of the ulnar nerve, and group B included 55 patients with suspected UNE in whom the diagnosis could not be established by MCV of the ulnar nerve.

INTERVENTIONS:

Not applicable.

MAIN OUTCOME MEASURES:

Differences between peak latencies of ulnar and median mixed nerve action potentials at the arm, after stimulating these nerves at the wrist. This was called mixed latency difference.

RESULTS:

The upper normative limit of the mixed latency difference was 1.1 ms, and there was a significant correlation with height. In group A, the mixed latency difference was abnormal in 80% of the cases and could not be calculated in 18%. In group B, the mixed latency difference was abnormal in 8 (15%) patients. All of these had abnormal "inching" of the ulnar nerve across the elbow.

CONCLUSIONS:

The mixed latency difference was particularly useful in cases of mild UNE.