Abductor Digiti Minimi and First Dorsal Interosseous Recordings for the Localization of Ulnar Neuropathy at the Elbow

ABSTRACT

OBJECTIVE: To compare abductor digiti minimi (ADM) recording with first dorsal interosseous (FDI) recording for the localization of ulnar neuropathy at the elbow. METHOD: The subjects were consisted of 28 patients of ulnar neuropathy at the elbow. The subjects were divided into 3 groups focal demyelination; focal demyelination and axonal degeneration; axonal degeneration. Compound muscle action potentials were recorded from both ADM and FDI muscles and ulnar nerve was stimulated at the wrist, 2 cm distal and 8 cm proximal to the medial epicondyle. Focal demyelination were analyzed into conduction block and/or conduction slowing. RESULTS: Conduction block was observed in 13 out of 28 patients (46%) with FDI recording and 11 out of the 28 patients (39%) with ADM recording. Conduction block was found solely with FDI recording in 3 patients, whereas 1 patient showed conduction block with ADM recording only. Concomitant segmental motor conduction slowing was observed in 11 out of 13 patients with FDI recording and in 6 out of 11 patients with ADM recording. CONCLUSION: Measurements to the FDI had a higher yield of abnormality than the ADM. In some patients, only one recording muscle showed abnormal findings. Therefore, it may be useful to record from both muscles to localize ulnar neuropathy at the elbow.