Background Sjögren's syndrome (SS) is a chronic and autoimmune disease characterized by inflammation of the exocrine glands. Nervous system dysfunction is a common and important complication in Primary Sjögren's syndrome (pSS) and may be the cause of significant morbidity. A wide variety of peripheral (PNS) and central nervous system (CNS) complications are among the severe complications of pSS. Autonomic system involvements are also reported in pSS. Electroneuromyography has been proved to be an useful confirmatory diagnostic tool, because all the clinically symptomatic patients with peripheral neuropathy or polyneuropathy presented electromyographic and nerve conduction abnormalities. Sympathetic skin response (SSR) is a noninvasive method that can be used easily to evaluate autonomic dysfunction. It involves a recordable skin potential change following the application of an internal or external stimulus. Although it has been used in a variety of clinical settings to evaluate sudomotor sympathetic function, literature does not reveal any studies using SSR in pSS.
Objectives The aim of this study was to show the possible autonomic involvement in patients with pSS.
Methods Peripheral nerve electrophysiological studies and the SSR were studied in 29 patients with pSS (inactive disease period) and 31 normal controls. Motor and sensory nerve conduction studies were performed in the median, ulnar, tibial, peroneal and sural nerves using a standard method. Motor nerve conduction velocity, distal motor latency, and compound muscle action potential were recorded for the median, ulnar, peroneal and tibial nerves. Sensory conduction velocity and sensory nerve action potential were assessed for median, ulnar and sural nerves.
For the palmar SSR, surface electrodes were used with the active recording electrode placed on the palm of the hand, and the reference electrode located at the wrist on the dorsum of the hand. SSR parameter included the latency in the onset of depolarization which was indicated by the first continuous deflection from the baseline. The amplitude was measured from peak to peak. Four successive SSRs were induced by unexpected acoustic stimuli, pinprick, touching and median nerve electrical stimulation at 30 mA stimulus intensity. The mean of these four latencies and amplitudes were taken as the valid value.
Results The latencies of SSRs were delayed (p=0.024) and the amplitude of SSR were decreased (p=0.010) in patients with pSS when compared with the control subjects. When the peripheral motor and sensory nerves' conduction parameters of controls were compared with the patients' values, only median motor compound muscle action potentials were significantly lower in the patients (p=0.021). There were no statistically significant differences among the remaining electrophysiological results.
Conclusions These findings reflect that sympathetic system is affected in pSS and this involvement is possibly seen before the peripheral nerve involvement. Our results suggest that SSR parameters may be used for early detection of any autonomic dysfunction in patients with PSS.
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Disclosure of Interest : None declared