Diagnostic values of conventional conduction parameters in ulnar neuropathy at elbow.

Abstract

Conventional parameters used in electrodiagnosis of ulnar neuropathy at elbow (UNE) are: (i) absolute across-elbow ulnar nerve motor conduction velocity (MCV), (ii) reduction rate of composed muscle action potential (CMAP) amplitude from above to below elbow stimulation, and (iii) MCV difference between forearm and across-elbow segment. We aimed to search the diagnostic accuracy values of these parameters on UNE, and their correlations with axonal dysfunction of ulnar nerve fibers. Arms with clinical signs of UNE and two-fold healthy controls were included. We detected the best cut off points of the measured parameters and their possible combinations. Their diagnostic accuracy values and correlations with parameters reflecting the axonal functions were analyzed, statistically. Totally, 118 arms with UNE and 236 controls were included. Absolute across-elbow MCV yielded a higher accuracy than MCV difference and reduction rate of CMAP amplitude (p = 0.010 and p˂0.001, respectively). Besides, combining it with other parameters did not increase the diagnostic yield. Correlation analyses revealed that the only parameter having positive linear correlations with sensory nerve action potential amplitudes both in the control and the disease groups is the absolute across-elbow MCV. The absolute across-elbow MCVs have also positive linear correlation with CMAP amplitudes in disease group. The absolute across-elbow MCV is the most valuable conventional parameter for the electrodiagnosis of UNE. It is also the most correlated parameter with the electrodiagnostic parameters reflecting the axonal functions of the ulnar nerve fibers.