Neuroelectrophysiological characteristics of peripheral neuropathy in primary Sjögren's syndrome: study protocol for a prospective case series and pre-preliminary results

Background and objectives: Sjögren's syndrome (SS) is a chronic progressive autoimmune disease. The incidence of peripheral nervous system damage in patients with primary SS (pSS) is 10–30%. Previous studies have shown that there are multiple electrophysiological manifestations in pSS patients presenting with peripheral neuropathy. However, there is no consensus on its neuroelectrophysiological manifestations. Peripheral neuropathy associated with pSS is easily confused with peripheral neuropathy of other etiologies. We hope to observe the neuroelectrophysiological manifestations of peripheral neuropathy associated with pSS to assist in the diagnosis of the disease. Design: A prospective case series. Methods: A total of 100 pSS patients with peripheral neuropathy receiving treatment in the Department of Neurology, First Affiliated Hospital of Kunming Medical University, China will be included in this study. Fifty-two patients presenting with peripheral neuropathy associated with pSS have been included in a preliminary investigation. Outcome measures and preliminary results: The primary outcome measure is the incidence of abnormal motor nerve conduction velocity in these patients. The secondary outcome measures are the incidences of abnormalities in terminal motor latencies, compound muscle action potential amplitudes, sensory nerve conduction velocities, sensory nerve action potential amplitudes, F waves, and sympathetic skin responses. The results of 52 patients included in the preliminary study showed that the incidences of each electrophysiological index was similar between the upper and lower extremities. Abnormal motor nerve conduction velocity occurred more frequently than abnormal compound muscle action potential amplitude. Abnormal sensory nerve conduction velocity was observed significantly more often than abnormal sensory nerve action potential amplitude. Abnormal motor nerve conduction velocity had a similar incidence to abnormal sensory nerve conduction velocity. Abnormal compound muscle action potential amplitude had a similar incidence to abnormal sensory nerve action potential amplitude. Abnormal F waves were observed significantly less frequently than abnormal motor nerve conduction study. Abnormal sympathetic skin response was seen with a similar incidence to abnormal motor nerve conduction study. Discussion: The results of this study, as indicated by the preliminary investigation, will reveal the neuroelectrophysiological abnormalities in peripheral neuropathy associated with pSS, which will aid diagnosis of the disease. Ethics and dissemination: This study was approved by Medical Ethics Committee of Kunming Medical University of China on October 14th, 2005 (approval No. 20051014). The study protocol was designed in September 2016 and registered in April 2018. The study protocol received ethics approval from Medical Ethics Committee of Kunming Medical University of China on October 14th, 2016 (approval No. 2016101411). Patient recuritment for the preliminary study was performed during January to October 2017. Patient recuritment for this study will begin in June 2018. Data collection will end in December 2020. The current study will be performed from June 2018 to December 2020. Results will be disseminated through presentations at scientific meetings and/or by publication in a peer-reviewed journal. Anonymized trial data will be published at www.figshare.com. Trial registration: This trial was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR1800015669).