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We studied phrenic nerve conduction times in 90 phrenic nerves of 45 normal subjects. The phrenic nerve was stimulated at the posterior border of the sternomastoid muscle in the supraclavicular fossa, just above the clavicle, with bipolar surface electrodes. For recording, positive and negative electrodes were placed on the xiphoid process and at the eighth intercostal bone-cartilage transition, respectively. We studied both the right and left sides to determine whether there was any difference between the two sides. The mean onset latency (± SD) of the right compound muscle action potentials (CMAPs) (5.99±0.39 msec) was significantly shorter than that of the left CMAPs (6.45±0.50 msec). The mean peak latency was significantly shorter in the right CMAPs (10.22±1.33 msec) than the left CMAPs (12.48±2.02 msec). The mean (± SD) amplitude was significantly lower in the left CMAPs (0.42±0.11 mV) than the right CMAPs (0.49±0.10 mV). The difference between the length of the nerve on the right and left sides might have affected the difference in latency between the two sides., Competing Interests: No potential conflict of interest relevant to this article was reported.

Nerve conduction studies performed between 1994 and 1996 on the median nerves of 204 hands of 113 patients [20 patients in hemodialysis (HD) with diabetic nephropathy, 27 without diabetes mellitus in HD for 10 years or more, 18 without diabetes mellitus in HD for less than 10 years, and 48 with diabetes mellitus not undergoing HD] were reviewed retrospectively to develop a discriminating tool that would better inform treatment selection for patients with carpal tunnel syndrome (CTS) in HD. Scatter diagrams were drawn from the results of this study, and a regression formula was obtained. Among the long-term HD patients without diabetic nephropathy, distal motor latency (DML) tended to increase without a significant concomitant reduction in motor nerve conduction velocity (MCV) in the forearm. In contrast, in HD patients with diabetic nephropathy, DML tended to increase and MCV was significantly lower despite shorter HD periods. The study showed that in HD patients, in whom the MCV(m/s) > 11[9 - DML(ms)], the surgical results might be excellent or good. The formula was tested against the results of the 30 surgical cases. The sensitivity of this formula was 0.84, and the specificity was 1.00. The formula produced a predictor of surgical results when used in conjunction with other criteria for CTS in HD patients, especially those with diabetic nephropathy.

Background: Nerve conduction study (NCS) is the only useful test for objective assessment of carpal tunnel syndrome (CTS). However, the relationship between pre- and postoperative NCS and clinical outcomes was unclear. This study aimed to determine whether pre- and postoperative (6 months) NCS could predict patient-oriented and motor outcomes (6 and 12 months postoperatively) in patients with CTS.Method: Of the 85 patients with CTS, 107 hands were analyzed from March 2011 to March 2020. All patients underwent open carpal tunnel release and were examined using the disabilities of the arm, shoulder and hand (DASH) questionnaire and grip strength (GS) preoperatively and 6 and 12 months postoperatively. Moreover, NCS was examined preoperatively and 6 months postoperatively. Distal motor latency (DML) and sensory conduction velocity (SCV) were the parameters used for NCS. The correlation coefficient between NCS and DASH or GS was calculated. A receiver operating characteristic curve was utilized to determine the NCS threshold value to predict DASH and GS improvement.Results: The average scores of GS preoperatively and 6 and 12 months postoperatively were 21.3, 22.3, and 22.8, respectively. On the other hand, the average scores of DASH preoperatively and 6 and 12 months postoperatively were 28.8, 18.3, and 12.2, respectively. The average NCS scores (DML and SCV) preoperatively/6 months postoperatively were 7.3/5.4 and 27.8/36.7, respectively. Preoperative NCS did not correlate with DASH and GS. Postoperative SCV correlated with the change in grip strength (6-12 months, r = 0.67; 0-12 months, r = 0.60) and DASH (0-12 months, r = 0.77). Moreover, postoperative DML correlated with the change in DASH (6-12 months, r = - 0.33; 0-12 months, r = - 0.59). The prediction for the improvement of GS/DASH achieved a sensitivity of 50.0%/66.7% and a specificity of 100%/100%, at an SCV cutoff score of 38.5/45.0 or above. The prediction for improvement of GS/DASH achieved a sensitivity of 83.3%/66.7% and a specificity of 100%/66.7% at a DML cutoff score of 4.4/4.4 or below.Conclusion: NCS at 6 months postoperatively can be used to predict the improvement of clinical outcome after 6 months postoperatively in patients with CTS. [ABSTRACT FROM AUTHOR]