The machines used were a Cadwell Sierra and a Neuromax Excel electrodiagnostic machines. Sensitivity, low-frequency filter, high-frequency filter, sweep speed, duration of pulse, and rate of pulse were not specified.

This study was performed in the supine position.

The authors used standard techniques but, for both median–sensory and ulnar–motor conduction techniques, they did not specify the methods chosen [1]. For median–sensory, they did not specify which finger was tested and if the orthodromic or antidromic method was performed. For the ulnar–motor, they did not specify from which muscle motor responses were recorded, after stimulation at the wrist (abductor digiti minimi, ADM, muscle or first dorsal interosseous, FDI, muscle). For the median–sensory, following the antidromic method, we recorded signals using surface electrodes placed to digit III (Fig. 1). For the median nerve (R1), the active recording electrode (A) was placed around the proximal interphalangeal joint of digit III; the reference electrode (R) was placed over the distal interphalangeal joint of digit III. For the ulnar nerve (R2), the active recording electrode (A) was placed on the motor point of the abductor digiti minimi (ADM) muscle; the reference electrode (R) was placed distally at the base of the digit V. The median and ulnar nerve recordings were made separately. The ground (G) electrode position was not specified; the figure shows the ground electrode placed on the palm.

Standard stimulations were applied over the median and ulnar nerves proximal to the distal wrist crease, separately (S1, S2).

Onset latency (ms) was measured from the stimulus onset to the onset of the negative peak of the sensory nerve action potentials (SNAPs). The distal motor latency was measured from the stimulus onset to the onset of the initial deflection of the compound muscle action potentials (CMAPs). The median–sensory–ulnar–motor latency difference (MSUMLD) was calculated subtracting ulnar–motor latency (from ADM muscle) to the median–sensory latency (to digit III). Skin and room temperatures were not given. Normal values (Table 1) were obtained from 68 hands of 34 patients with normal nerve conduction studies (32 women and 2 men, mean age 47 years). Authors also performed the technique on a total of 111 hands from 76 patients (Table 2), so divided: 23 hands of 18 patients with symptoms and findings referable to carpal tunnel syndrome (CTS) but normal nerve conduction studies (5 bilateral, 12 women and 6 men, mean age 45 years – probable CTS Group), and 88 hands of 58 patients with CTS diagnosed by standard criteria (30 bilateral, 57 women and 31 men, mean age 50 years – definite CTS Group). Pathological waveform and values in a CTS case are reported (Fig. 2).