Sensitivity, low-frequency filter, high-frequency filter, sweep speed, duration of pulse, rate of pulse, and machine used were not specified.

This study was performed in the supine position.

Following an orthodromic method [1] similar to that used by Buchthal et al. in 1974 [2], needle recording electrodes were placed at the wrist (R1, R2) for both the median and ulnar nerve recordings. An active recording needle (A) electrode was placed over the median nerve (R1) and over the ulnar nerve (R2) at the wrist. The reference needle (R) electrodes were placed at the wrist, at the same level as the recording electrodes (3–4 cm distance), radial–dorsal for the median nerve recording, and ulnar–dorsal for the ulnar nerve recording (Fig. 1). For the median nerve recordings, the authors placed the reference electrode radial to the active median electrode to reduce significantly the contamination from the ulnar nerve. They adjusted the recording electrodes near the median nerve, using the threshold of the motor-evoked response in the APB muscle. Ground (G) electrode position was not specified, the figure shows the ground electrode placed on the palm.

Digit IV (ring finger) was stimulated via ring electrodes placing the cathode around the proximal interphalangeal joint of digit IV. The anode was placed distally around the distal interphalangeal joint of digit IV.

Following the method by Buchthal et al. [2], the 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 to the positive peak of the SNAP. The distance measurement was conventional. When calculating the sensory nerve conduction velocity (SNCV) over the digit–wrist segment, distance (mm) was divided by the latency (ms). Skin temperature of the fingers, wrist, and elbow was kept at 33–37 °C using an infrared heating lamp. Normal values (Table 1) were obtained from 23 healthy volunteers (sample data were not given), and pathological data (Table 2) were recorded from 38 patients (26 women and 12 men, mean age 53 ± 14 years) with carpal tunnel syndrome (CTS).