Is There Any Sympathetic Skin Response (SSR) Abnormality in Raynaud Phenomenon

Objectives: Sympathetic skin response (SSR) is a technique for assessment of the damage of peripheral neuropathies and the disorders of the sympathetic system. This study aimed to evaluate SSR among patients with Raynaud phenomenon (RP). Methods: Between January 1, 2015 and December 30, 2018, about 20 patients with RP and 20 healthy subjects as the control group were recruited from patients referring to the Outpatient Clinics of Shiraz medical University. All the participants were clinically examined, and the SSR was performed using a standard protocol. SSR is abnormal when the latency is prolonged and/or the amplitude reduced. Results: Raynaud's group consisted of 19 women (95 %) and 1 male (5%). 3 patients (15 %) with primary Raynaud's phenomenon (PRP) and 17 patients (85%) with secondary Raynaud's phenomenon (SRP). The control group consisted of 16 women (80%) and 4 males (20%). The mean age of the Raynaud's group and control subjects was 43.1±9 and 36.7±8.6 years, respectively. The SSR to the electrical stimulus was absent in 3 patients (PRP patients). The total median nerve mean latencies in the upper limb were 1.9±0.57 and 1.19±0.52 seconds for the Raynaud's group and control groups, respectively (p <0.001). These findings revealed significantly prolonged SSR latencies in the Raynaud's group, while the mean amplitude showed no significant differences in both groups (p =0.756). Conclusion: Absence or prolonged latency of SSR was associated with the disorders of the unmyelinated axons in the sympathetic system. Our findings suggested the disorders of unmyelinated axons in Raynaud's phenomenon. Keywords: Raynaud Disease; Autonomic Nervous System; Electrodiagnosis; Sympathetic Fibers; Nerve Conduction.