Prevalence of Small A-Delta Fiber Neuropathy in Sjögren’s Disease: Findings from a Cohort Study

Polyneuropathy is a common condition that limits the quality of life among patients with primary Sjögren disease (pSjD). Somatic sensory fiber neuropathy involving small myelinated (A-δ) and unmyelinated C fibers may precede the development of sicca syndrome. The cutaneous silent period (CSP) is an inhibitory spinal reflex that can be used as a tool for evaluating the dysfunction of A-δ fibers. This study sought to examine CSP parameters, and their correlates, in patients with pSjD vs. healthy controls. We recruited 134 consecutive patients with a diagnosis of pSjD, of whom 109 subjects were included in the analysis. Electrodiagnostic tests comprised a nerve conduction study (NCS) and CSP analysis, alongside laboratory tests and questionnaires (the ESSPRI and SF-36). The examination of the healthy control (HC) group consisted of 113 NCSs and CSP studies. NCS tests of the median nerve in both groups were within the normal range. Statistical analysis revealed a significant difference in CSP duration (<i>p</i> < 0.001), S1 latency (<i>p</i> < 0.001) and S2 latency (<i>p</i> < 0.001) between the pSjD and HC groups. We observed prolonged CSP duration in approximately 38% of patients with pSjD and prolonged S2 latency in 18.35%. Small A-delta fiber neuropathy was diagnosed in 38% (41 subjects) patients. A regression analysis of CSP parameters indicated an association between the age of patients and PM Scl-75 antibodies (ab) levels in the pSjD cohort. As a new, noninvasive method of assessing A-δ nerve fibers, CSP was found to have a relation to the age and PM Scl-75 antibodies in patients with pSjD. The utility and sensitivity of CSP as a test for screening A-δ fiber function require further investigation in large cohorts of the pSjD population.