The importance of arm-elbow velocity difference in the diagnosis of ulnar neuropathy at the elbow

Objective: Diagnosis of ulnar neuropathy at the elbow (UNE) by measuring the forearm-elbow velocity difference (FEVD) is subject to significant limitations because Wallerian degeneration might occur in severely affected patients. The contribution of the arm-elbow velocity difference (AEVD) in the diagnosis of UNE may be more valuable because this segment is less affected by pathologic changes. Methods: The charts of patients who were diagnosed as having UNE were reviewed. Ulnar neuropathy at the elbow was classified as mild, moderate or severe. Motor nerve conduction studies of the ulnar nerve were performed with the elbow flexed to 90 degrees in the supine position. Needle electromyography, as well as sensory and mixed nerve conduction studies, were also performed. Electrophysiologic findings were compared with controls. Results: The upper limit of FEVD and AEVD were 14.2 m/s and 21.8 m/s, respectively. In UNE, 13 of 23 limbs (56.5%) had AEVD abnormality, and 14 (61%) limbs demonstrated FEVD abnormalities. Arm-elbow velocity difference or FEVD abnormalities were present in 82.6% of UNE extremities. There was no statistically significant difference between AEVD and FEVD abnormalities in patients with mild, moderate or severe UNE. The evaluation of patients without sensory and mixed nerve conduction abnormalities revealed an increased AEVD in 6 (75%) out of 8 limbs. Conclusion: Diagnostic sensitivity of UNE is increased when FEVD and AEVD are evaluated together. The detection of high rates of AEVD abnormalities in patients without sensory and mixed nerve abnormalities supports the usefulness of this measure.