Diagnostic Value of Compound Nerve Action Potential in Ulnar Neuropathy at the Elbow

Abstract

Background: Ulnar neuropathy is the second most common neuropathy of the upper extremity. However, routine electrodiagnostic tests may not reveal some cases. To determine the diagnostic value of compound nerve action potential (CNAP) of the ulnar nerve as a complementary test, this study was done.

Methods: In a cross-sectional analytical study, 34 subjects (68 limbs) who had presented with clinical symptoms and signs of the ulnar neuropathy were evaluated with CNAP. Then the subjects were re-evaluated with standard electrodiagnostic tests. Subjects with neuropathy based on standard electrodiagnostic tests were assigned to the patient group and those without it were assigned to the healthy group. Data were analyzed with the use of receiver operating characteristic (ROC) analysis.

Results: The latency and amplitude parameters had diagnostic value given the significance of the area under the ROC curve. In relation to the latency parameter, the two thresholds which had relatively acceptable accuracy were 0.2 ms and 0.7 ms; in patients in whom the difference between the peak latency of the healthy and symptomatic sides was more than 0.7 ms, at likelihood ratio positive (LR⁺) = 5.7 and specificity = 95%, the results were in favor of ulnar neuropathy.

Conclusion: CNAP evaluation has diagnostic value and can be used as an adjunct to other diagnostic techniques in suspected cases of ulnar neuropathy in the elbow region.