Limitations on the clinical utility of the ulnar dorsal cutaneous sensory nerve action potential.

ABSTRACT

OBJECTIVE: To validate the clinical use of the ulnar dorsal cutaneous (UDCN) sensory nerve action potential (SNAP) in the topographical analysis of ulnar mononeuropathies and in the process of choosing a sensory nerve for biopsy. METHODS: We surveyed the UDCN SNAP electrophysiological characteristics in both hands of 97 normal volunteers aged 10-84 years. The nerve was recorded from the 4th intermetacarpal space with subcutaneous needle electrodes and percutaneous stimulation was carried out at the wrist. RESULTS: In agreement with other studies, the mean conduction velocity was 58. 6+/-6.7 m/s, but the mean and the lower normal value of the amplitude (32 and 14.7 microV) were significantly higher than previous known data. An important finding was that in 21% of our population study, the UDCN SNAP was absent on at least one side, or a significant degree of asymmetry between the left and right sides was present. CONCLUSION: The UDCN SNAP is technically easy to obtain, but the high frequency of asymmetric or absent potentials detected in this study implies that caution should be taken in using this SNAP in clinical practice.