ABSTRACT
Objective: The present study aimed to assess the sensitivity and specificity of nerve conduction studies (NCS) in patients pre-diagnosed with ulnar neuropathy at the elbow (UNE).
Method: This study assessed 166 extremities of 124 patients (68females, 56males) using electroneuromyographic (ENMG) testing. Nerve conduction velocity (NCV), sensory nerve action potential (SNAP) amplitudes, and compound motor action potential (CMAP) amplitudes were obtained by stimulating the ADM and FDI muscles. Patients were divided into two groups based on diagnosis made after ENMG testing; the UNE group (11 patients) and the non-UNE group (114extremities of 84 patients).The remaining 41 extremities (15 females and14 males) with non-UNE ENMG pathologies were excluded from the data set. Sensitivity and specificity values of the motor nerve conduction studies at the abductor digiti minimi(ADM) and first dorsal interosseous (FDI) muscles were determined. NCV of the forearm segment of the ulnar nerve was subtracted mathematically from the NCV of the elbow segment to determine the effectiveness of the forearm-elbow inter-segmental velocity difference (FIVD)for the diagnosis of UNE.
Result: Agreement between the pre-diagnosis and the electrophysiological diagnosis of UNE was 6.7%. Ulnar CMAP amplitudes of the ADM at the elbow segment and SNAP amplitudes at the elbow segment were similar (p>0.05).Reduced CMAP amplitude had 100% sensitivity and specificity. Sensitivity and specificity rates for NCV from the FDI were 99.1% and 81.8%, respectively, and 98.2% and 90.9%, respectively from the ADM. Sensorial, ADM and FDI FIVD sensitivity rates were 81.8%, 81.8%, and 72.7%, respectively, and specificity rates were 86.8%, 78.1%, and 90.2%, respectively.
Conclusion: Agreement between clinical pre-diagnosis and ENMG diagnosis of UNE was very low. However, the determination of reduced amplitude and NCV in the elbow segment of the ulnar nerve using ENMG had high sensitivity and specificity. In such patients, FIVD may be useful in diagnosing UNE.
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