Cutaneous Silent Period Assessment in Primary Sjögren's Syndrome

CSP recordings are performed in the upper extremities using the same surface bar recording electrodes. Filters are set at 2 Hertz (Hz) to 10 kilo Hz, sensitivity is 200 microVolts (µV) and sweep speed is set at 200 milliseconds (ms). Stimulating electrode is placed on the index finger and recording bar electrode is placed on the abductor pollicis brevis (APB) muscle. During steady submaximal (50% of the maximal contraction) thumb abduction, 10 consecutive painful electrical stimuli of standard 80-milli Ampere (mA) intensity and 0.5-ms duration are applied to the index finger and responses are superimposed. CSP latency and duration are calculated and recorded. CSP latency is defined as the time between the stimulation and the onset of the silent period. CSP duration is calculated as the time interval between the beginning and end of the CSP.