Analysis of peripheral nerve and autonomic nervous system function and the stage of microangiopathy in patients with secondary Raynaud's phenomenon in the course of connective tissue diseases.

Background. The pathogenesis of secondary Raynaud's phenomenon (SRP) associated with connective tissue diseases (CTD) is not entirely understood. Nervous system dysfunction and microangiopathy are considered to be causes of this pathology. Objectives. Peripheral and autonomic nervous system function, the stage of microangiopathy, and the relationships between these in patients with SRP were analyzed. Material and methods. In the study, 20 patients with CTD-related SRP and 30 healthy controls were subject to capillaroscopy, standard conduction velocity tests and conduction velocity distribution (CVD) tests in ulnar and peroneal nerves, heart rate variability (HRV), and sympathetic skin response (SSR) tests. Results. There were no significant differences in the standard motor and sensory conduction velocity tests, or in CVD tests in the ulnar and peroneal nerves in SRP patients compared with the controls. The patients with SRP had a significantly lower SSR amplitude and longer latency in hands and feet. The patients with CTD-related SRP had a significantly lower mean HRV with higher low frequency (LF) values in the spectral analysis and expiration/inspiration ratio (E/I) during deep breathing. There was no correlation between the stage of microangiopathy and neurophysiological test results. Conclusions. Correct standard conduction velocity and CVD testing in patients with SPR suggest that vasomotor disturbances may occur in CTD regardless of peripheral neuropathy. The lack of relationship between SSR and microangiopathy could confirm that these 2 processes occur independently in patients with CTD-related SRP. Autonomic nervous system impairment together with normal peripheral nerve function suggest the central origin of CTD-related SRP.