Sensory nerve area measurements in patients with diabetic neuropathy

Sensory nerve potential area measurements may reflect the properties of underlying nerve fibres better than amplitude or conduction velocity measures. The terminal segment of the sensory curve may contain activity of regenerating nerve fibres. The reliability of area measurements of sensory potentials obtained with surface recording techniques is unknown. We scanned sural nerve sensory potential curves and measured the areas under different parts of the curve in 52 reference and 73 diabetic polyneuropathy (DPN) patients. The variability of repeat testing in reference subjects for total area was 12% and for the terminal segmental area (TSA) was 19%. In DPN patients, the total area variability was 17% and TSA variability was 24%. This compares to amplitude variability of 8% in reference subjects and 10% in patients with DPN. These results demonstrate that sensory potential area measurements are feasible, but highly variable. We conclude that current clinical trials do not include sufficient numbers of patients to show change in area measurements, particularly the area under the terminal segment of the curve.