However, due to the presence of ongoing denervation, surgical referral was made. We cannot always precisely localize the site of entrapment in ulnar neuropathies, although inching studies can often differentiate retrocondylar compression from compression in Guyon s canal. Typically, surgery will involve releasing all potential sites of entrapment about the elbow. However some surgeons prefer not to transpose the ulnar nerve in every case. Compression at Guyon s canal would not explain the more proximal denervation, nor obviously the drop in NCV and CMAP amplitude across the elbow.
Electrodiagnostic technique is very important in evaluating suspected ulnar nerve pathology.
The elbow should be flexed to between 90 and 135 degrees. Across elbow NCV may appear falsely slowed if the study is done with the elbow fully extended. Additionally, care should be taken to ensure that one uses the lowest possible stimulus that yields a supramaximal response. This can in turn lead to a falsely low velocity reading in the next most proximal segment. American Association of Electrodiagnostic Medicine Quality Assurance Committee.