Subclinical pronator syndrome in patients with carpal tunnel syndrome: An electrophysiological study

Abstract

Aim of the work: The aim of the present study was to detect subclinical pronator syndrome (PS) in patients with carpal tunnel syndrome (CTS) with the utility of the anterior interosseous/median (AIM) score. Patients and methods: The present study included 90 clinically diagnosed CTS hands and 60 asymptomatic hands of healthy volunteers as a control group. Clinical examination was done for all patients. The following tests were done: (1) Sensory nerve conduction studies: median and ulnar nerves; (2) Motor nerve conduction studies: median and ulnar nerves as well as the anterior interosseous nerve recording the pronator quadratus muscle with calculation of the AIM score. AIM score is a ratio of the antecubital motor latency of the anterior interosseous nerve to that of the median nerve. Results: There were 71 CTS hands (78.9%) with a median distal latency (DL) exceeding the reference value and the AIM score was decreased in 63 (70%) of them. Eight hands (8.9%) had a prolonged median DL associated with an AIM score within the reference range raising the probability of having PS. Five (5.6%) of these eight hands had electrophysiological findings in consistency with an established PS. The sensitivity of AIM for the concomitant detection of PS with CTS was 100% and the specificity 95.4%. None of the controls had PS. Conclusions: Subclinical PS is found in CTS patients and could be searched for electrophysiologically in those patients with evidence of moderate to severe degrees of CTS and the AIM score is useful in this aspect.