Median and ulnar palm-wrist studies

Objectives: Routine carpal tunnel electrodiagnosis frequently includes medi an (MPW) and ulnar (UPW) palm-wrist mixed nerve conduction latency determin ations over 8 cm. Despite widespread use, normative palmar latency differen ce (PLD) and UPW values, and the relative utility of onset latency (OL) or peak latency (PL) measurements are controversial. The current study was con ducted to determine normative values for these parameters. Methods: MPW and UPW studies were performed unilaterally in 33 normal contr ols. The PLD-OL and PLD-PL were calculated. The mean, range, standard devia tion, and upper limits of normal were determined. 74 hands (50 patients) wi th both clinical and electrophysiologic median neuropathy were also studied . Results: The abnormal MPW and UPW cut-offs were both 1.8 ms (OL), and 2.3 m s (PL). The abnormal PLD cut-offs were 0.5 ms (OL and FL). Using either OL or FL, PLD parameters were similar within controls, and also within CTS pat ients. Using either OL or FL, UPW parameters were similar between controls and CTS patients. Conclusions: An abnormal PLD cut-off of 0.5 is recommended. This is slightl y higher than some prior recommendations, however it should minimize the li kelihood of false positive studies. Onset and peak latency measurements are likely to have similar clinical utility. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.