Sensitivity was 10 μV/division, low-frequency filter was 20 Hz, high-frequency filter was 2 kHz, sweep speed was 1.5 ms/division, and the machine used was a two-channel Medelec Synergy Oxford Instrument. Duration of pulse and rate of pulse were not specified.

This study was performed in the supine position with the thumb (digit I) in the maximal palmar abduction.

Following the antidromic method [1] proposed previously by Bergeron and Braddom [2], the median sensory nerve conduction study was performed recording the action potentials from the palmar cutaneous branch (PCB) over the thenar eminence (Fig. 1). The active recording (A) electrode was placed on the skin of the midthenar eminence at the halfway point on an imaginary line connecting the ulnar aspect of the first metacarpophalangeal joint and the palmaris longus (PL) tendon as it crossed the distal wrist crease. The reference (R) electrode was placed distally toward the base of the digit II (index finger). The ground (G) electrode position was not specified in the text, probably because it was placed on the back of the hand (the figure shows the ground electrode placed on the palm).

Sensory nerve conduction study was done antidromically. The wrist to thenar sensory nerve conduction study was done stimulating the median nerve at the wrist (S) 2 cm proximal to the proximal wrist crease. Stimulation was applied on the median nerve, between the tendons of the flexor carpi radialis (FCR) and the palmaris longus (PL) muscles.

Sensory nerve conduction velocity (SNCV) was calculated using the onset latency of the first negative peak and measured in meter per second (m/s). The evoked SNAP typically had two negative peaks followed by the motor potential. The first negative peak represented the palmar cutaneous median branch (PCBm); the second peak was a far-field potential. Sometimes a third negative peak occurred at a longer latency than PCBm SNAP and represented the digit I median SNAP [2]. Negative peak amplitude (μV) was measured from the baseline to the negative peak of the potential. The authors had not taken peak-to-peak amplitudes because of the close proximity of the second negative peak (far-field potential) to the first negative peak (SNAP of PCBm). Skin temperatures were measured over the palmar wrist; all tests were performed at a temperature above 30 °C. The authors studied 59 hands (Table 1) from control subjects (14 men and 17 women, age range 26–66 years, mean age 46 years) and 57 hands (Table 2) from 35 patients (25 women and 10 men, age range 33–82 years, mean age 53 years) with clinically diagnosed carpal tunnel syndrome (CTS).