OBJECTIVE: To determine utility of comparative electrophysiological techniques in differentiating carpal tunnel syndrome (CTS) in the background of diabetic polyneuropathy (DPN). DESIGN: Ninety diabetic patients were classified into three groups: normal, CTS, and DPN according to nerve conduction studies (NCSs). The patients in the DPN group were divided into two subgroups of DPN and DPN-CTS according to clinical criteria. The comparative electrophysiological parameters including median-radial sensory distal latency difference (M-RSLD), median-ulnar sensory distal latency difference (M-USLD) and lumbrical-interosseous median-ulnar distal latency difference (LIMULD) were compared in subgroups of DPN, DPN-CTS and CTS. RESULTS: Thirty-five (38.8%), 47 (52.3%), and 8 (8.9%) patients were diagnosed as CTS, DPN, and normal, respectively, according to NCS. After clinical stratification, 25 patients were diagnosed as DPN and 22 patients were diagnosed as DPN-CTS. The mean M-USLD and LIMULD values were similar in CTS and DPN-CTS groups, but larger than DPN statistically (p<0.05 for all). LIMULD, M-RSLD and M-USLD were positive in 88.4, 73 and 54% in the DPN-CTS group, respectively. CONCLUSIONS: Electrophysiological abnormalities were common in diabetic patients and LIMULD can identify CTS in diabetic DPN patients better than M-RSLD and M-USLD.
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