The machines used were a Nicolet Viking IV and a Dantec Key Point 4 electromyograph. Sensitivity, low-frequency filter, high-frequency filter, sweep speed, duration of pulse, and rate of pulse were not specified.

This study was performed in the supine position.

Following the orthodromic method [1], for measurement of the direct forearm median mixed nerve amplitude and conduction velocity, signals were recorded proximally at the elbow (R), just above the crease of the antecubital fossa and medial to the biceps tendon (Fig. 1). The authors used a pair of 1-cm-diameter stainless steel disk electrodes. For the measurement of the derived forearm median mixed nerve conduction velocity, mixed responses were recorded at the wrist (R1), 8 cm proximal to the stimulating cathode, and proximally at the elbow (R2), just above the crease of the antecubital fossa and medial to the biceps tendon (Fig. 2). The reference (R) electrode was proximal. The ground (G) electrode position was not specified (the figure shows the ground electrode placed over the forearm).

Following the orthodromic method, for measurement of the direct forearm median mixed nerve amplitude and conduction velocity, the median nerve was stimulated at the wrist (S). For measurement of the derived forearm median mixed nerve conduction velocity, the median nerve was stimulated on the palm (S) – 8 cm distal to the active recording electrode at the wrist. The authors used a supramaximal nerve stimulation.

Onset latency (ms) was measured from the stimulus onset to the onset of the negative peak of the mixed responses. Negative peak amplitude (μV) was determined from the onset to the peak of the negative peak of the mixed response. For measurement of the direct forearm median mixed nerve conduction velocity (m/s), the distance between the stimulating cathode to the active recording electrode was measured (wrist–elbow segment) and divided for the wrist–elbow conduction time; for the measurement of the derived forearm median mixed nerve conduction velocity (m/s), the distances between the stimulating cathode (palm) to the active recording electrodes (at the wrist and at the elbow) were measured (palm–wrist and palm–elbow segments) and divided for the subtraction of the conduction time of the palm–elbow and palm–wrist segments (in this way the authors derived the wrist–elbow conduction time). Surface temperature of the hand was measured and maintained at or above 32 °C. Normal values (Table 1) were obtained from 75 control subjects (mean age 49.75 ± 12.10 years); pathological values (Table 2) were recorded from 75 patients (mean age 48.04 ± 10.55 years) with carpal tunnel syndrome (CTS).