Sensitivity was 5 μV/division, sweep speed was 5 ms/division, duration of pulse was 0.2 ms, and the machine used was a DISA 14C11. Low-frequency filter, high-frequency filter, and rate of pulse were not specified.

This study was performed in the supine position.

Following the orthodromic method [1], using needle electrodes, signals were recorded at two different points (Figs. 1 and 2): at the wrist (R1) and at the elbow (R2). To record from sensory nerve fibers at the wrist and elbow, a stainless steel needle with a bared tip of 0.3 cm was placed near the nerve at a standard position; the remote electrode was placed at the same level as the near-nerve electrode at a distance of 4–6 cm from it. At the wrist (R1), the subdermal electrodes (both active and reference electrodes) were inserted proximally to the distal wrist crease. At the elbow (R2), the electrodes were placed over the median nerve on the antecubital fossa. Ground (G) electrode position was not specified in the report; the figure shows the ground electrode placed on the palm.

Digit I (thumb) or digit III (middle finger) was stimulated maximally with current values of 50–70 mA using surface electrodes (Velcro straps) or 20–30 mA using subdermal electrodes (needles); duration of current pulse was 0.2 ms. The active stimulating electrode was placed medially and laterally at the proximal end of the distal phalanx of digit I or at the middle phalanx of digit III. The reference electrode was placed 2 cm distally from the active electrode.

Latency was measured from the stimulus onset to the initial positive peak of the sensory nerve action potential (SNAP). Peak to peak amplitude was measured from negative peak to positive peak of the SNAP (authors used a log scale for the amplitude of the sensory potential recorded from the median at the wrist). Distance measurement was conventional. When calculating the sensory NCV over the digit–wrist segment, distance (mm) was divided by the latency (ms). When calculating the sensory NCV over the wrist–elbow segment, the distance was divided by the latency difference between the elbow and the wrist. The temperature of the surface of the arm was kept at 36–38 °C corresponding to 35–37 °C near the nerve using an infrared heating element (500 W) placed about 20 cm above the extremity. Normal values (Table 1) were obtained from 190 control subjects (sample data were not given); pathological values (Table 2) were recorded in 117 patients with signs and symptoms of carpal tunnel syndrome (CTS) – mean age is 55 years, 11 patients were 30 years old or less, and 84 were women and 33 were men.