Sensitivity was 10 μV/division, low-frequency filter was 20 Hz, high-frequency filter was 2 kHz, sweep speed was 2 ms/division, duration of pulse was 0.2 ms, and the machine used was a Dantec Cantata. Rate of pulse was not specified.

This study was performed in the supine position. The forearm, wrist, and hand were stabilized with Velcro on a comfortable board.

Following the orthodromic method [1], the sensory ultra-distal testing (SUDT) of all digits (digit I–V) of both hands was performed recording with a bipolar fixed distance (2.2 cm) surface electrode placed at the wrist over the median nerve for digit I, digit II, digit III, and digit IV (R1) stimulations and at the wrist over the ulnar nerve for digit V (R2) stimulation (Fig. 1). The active electrode (A) was placed proximal to the stimulating cathode (−), ideally proximal to the distal wrist crease; the reference (R) was placed distally. Each recording was made separately. The ground (G) electrode position was not specified in the report; the figure shows the ground electrode placed on the palm.

Sensory ultra-distal testing (SUDT) of all digits (digit I–V) of both hands was performed stimulating at the pulp or slightly proximal with a bipolar electrode at a fixed distance (2.3 cm). The current duration of 0.2 ms and supramaximal intensity (between 8 and 15 mA) were used for stimulations. The cathode (−) was placed proximally to the active recording electrode to the wrist (R). Each digit was stimulated separately and recorded at the wrist: digits I, II, III, and IV (S1, S2, S3, and S4) were stimulated and recorded at the wrist on the median nerve (R1); digit V (S5) was stimulated and recorded at the wrist on the ulnar nerve (R2).

Onset latency (ms) was measured from the onset of the stimulus to the onset of the negative deflection of the sensory nerve action potential (SNAP). Peak-to-peak amplitude (μV) was measured from the negative peak to the positive peak of the SNAP. The number of sweeps on average varied from 5 to 50 depending upon the amplitude of the SNAP. Skin temperature was greater than 31 °C. The author studied 20 control (Table 1) subjects (12 women and 8 men, age range 24–85 years) and 5 patients (Table 2) – 5 women (age range 27–61 years, mean age 44 years) who had experienced nocturnal paresthesias and numbness in the right median nerve distribution at least 1–15 months, mean 7.9 months.