Ulnar to median nerve minimum F-wave latency difference in confirmation of ulnar neuropathy at elbow.

OBJECTIVE

To analyze the utility of ipsilateral ulnar to median nerve F-wave latency difference in confirmation of ulnar neuropathy at elbow (UNE).

METHODS

Data of all UNE patients referred to the electroneuromyography laboratory were prospectively collected. Diagnoses were based on the presence of typical symptoms and signs. Motor and sensory conduction studies and F-wave studies were performed on both extremities of all the patients. Ulnar nerve across-elbow motor conduction velocity was calculated for both sides, and an inching test was carried out on symptomatic side. F waves were elicited with 16 supramaximal stimuli and recorded over abductor digiti minimi muscle for ulnar nerve and abductor pollicis brevis muscle for median nerve. Difference between minimum F-wave latency of ulnar nerve and one of median nerve is calculated for each arm. Data of healthy arms were used as control values.

RESULTS

Thirty-four arms of 17 patients with left-sided UNE were included. In all affected arms, minimum F-wave latency of ulnar nerve is longer than one of median nerve (minimum difference, 1.05 milliseconds; maximum difference, 10.9 milliseconds). In all the patients, F-wave latency difference of affected side was greater than one of healthy side. Best cutoff value for F-wave latency difference was calculated as 2.20 milliseconds on detection of UNE. F-wave latency difference was more than 2.20 milliseconds in 16 affected arms, whereas it was more than 2.20 milliseconds in only one healthy arm. Therefore, the sensitivity and specificity were detected as 94.1% and 94.1%, respectively.

CONCLUSIONS

Our results revealed that UNE could be confirmed easily with F-wave latency difference studies with a high sensitivity and specificity. This finding should be validated with further studies, which have larger study populations.