Sensitivity was 4–10 μV/division, low-frequency filter was 10 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 TECA TD20 two-channel electrodiagnostic unit. Rate of pulse was not specified.

This study was performed in the supine position.

The authors [1] performed three different nerve conduction techniques: (1) Following the orthodromic method, mixed nerve action potentials (MNAPs) were recorded proximally at the arm (R1) and at the axilla (R2), 35 and 25 cm distal to the sternal notch (measured with the arm externally rotated and abducted to 90 °C), respectively (Fig. 1). Authors used stainless steel disks 1 cm in diameter applied with conductive gel, and the optimal location of the active recording (A) electrode was determined as the site at which submaximal stimulation produced the largest visible contraction in the distal median innervated muscles. A reference (R) electrode was placed 6 cm from the active recording electrode, perpendicular to the course of the median nerve. The authors used unipolar recordings to avoid variable summation and subtraction from bipolar recordings, in which both electrodes record a significant nerve potential. (2) Following the orthodromic method (1), authors suggested an additional median MNAP study including stimulation across the carpal tunnel, on the palm – 4 cm distal to the wrist stimulation site, recording from the arm electrodes (Fig. 2). Usually, 8–12 potentials (in some cases 16) were averaged to record the MNAPs proximally from the arm and axillary electrodes. (3) Following the orthodromic method [1], sensory nerve action potentials (SNAPs) were recorded at the arm (Fig. 3), using the same electrode placement for MNAPs recording (orthodromic methods 1 and 2). Ground (G) electrode position was always placed between the stimulation and recording sites (figure shows ground electrode placed on the forearm).

(1) Following the orthodromic method, the median nerve was stimulated at the wrist (S), 14 cm proximal to the midproximal phalanx of the digit II. (2) Following the orthodromic method, the median nerve was stimulated on the palm (S1), 4 cm distal to the wrist stimulation site, and at the wrist (S2), 14 cm proximal to the midproximal phalanx of the digit II. For both methods, the supramaximal nerve stimulation was performed (the stimulus intensity was gradually increased to elicit appropriate muscle contractions and until no appreciable increase in MNAP amplitude occurred, using 0.2 ms duration). (3) Following the orthodromic method, sensory nerve responses (SNAPs) were obtained after stimulation to the digit II. The authors used ring electrodes for SNAP recording, placing the cathode at the midproximal phalanx and the anode at the distal phalanx.