Sensitivity was 20 μV/division, low-frequency filter was 20 Hz, high-frequency filter was 10 kHz, sweep speed was 1 ms/division, and the machine used was a TECA (model was not specified). Duration and rate of pulse were not specified.

This study was performed in the supine position, with the elbow and fingers slightly flexed.

Following the antidromic method [1], signals were recorded distally from the elbow at the wrist (R). A pair of 8-mm disc surface electrodes was placed proximal to the wrist crease; the active recording electrode (A) was placed 4 cm proximal to the wrist crease (Fig. 1). The ground (G) electrode position was not specified; it can be placed over the skin of the forearm (between the stimulating and the recording electrodes) or on the dorsum of the hand (the figure shows the ground electrode placed over the forearm).

The median nerve was stimulated at the elbow (S), just above the crease of the antecubital fossa and medial to the biceps tendon at the elbow, which allowed direct measurement of the median forearm nerve action potential (FNAP). Supramaximal nerve stimulation was applied at the antecubital fossa using a handheld bipolar stimulator.

Distal peak latencies (ms) were measured from the beginning of the shock artifact to the peak of the negative deflection of the evoked FNAP. The peak latency, rather than the onset latency (based on the initiation of the FNAP response), was chosen because it provided a more reproducible measurement. The distance between the cathode and the active recording electrode was measured using a fiberglass reinforced tape. The peak latency time (peak latency of the FNAP) measurement was divided into the stimulator-to-recording distance (forearm–wrist distance) in order to calculate the direct nerve conduction velocity (NCV) of the forearm nerve action potential (FNAP). The skin temperature in the palm was maintained at a minimum of 32 °C. Normal values (Table 1) were obtained from 16 asymptomatic control subjects (mean age 33.9 ± 12.5 years, age range 21–63 years). The authors also studied 21 patients (mean age 41.2 ± 13.5 years) with carpal tunnel syndrome (CTS). Pathological sample data were not given (Table 2).