Carpal tunnel syndrome in systemic sclerosis: prevalence, clinical correlates, and diagnostic performance of ultrasound compared with nerve conduction studies

Carpal tunnel syndrome (CTS) is a frequent yet under-recognized complication in systemic sclerosis (SSc), where hand symptoms may overlap with vasculopathy and musculoskeletal involvement. Consequently, diagnosis often requires nerve conduction studies (NCS), while the role of ultrasound remains incompletely defined. We aimed to determine the prevalence of CTS in SSc using NCS as the reference standard, identify associated clinical and disease-related factors, and assess the diagnostic performance of ultrasound. We conducted a cross-sectional study including consecutive SSc patients recruited from the Rheumatology Unit of Colentina Clinical Hospital, Bucharest, Romania (January 2023-March 2025). All participants underwent standardized clinical examination, comprehensive musculoskeletal ultrasound, and NCS within a 7-day interval. The ultrasound protocol incorporated multiple structural and dynamic parameters of the median nerve, including maximal cross-sectional area (maxCSA) and complementary measurements. CTS was defined and staged electrophysiologically according to the Bland scale. Associations were analyzed using clustered generalized estimating equation models accounting for bilateral hands. Ultrasound diagnostic performance was evaluated using maxCSA thresholds and receiver operating characteristic analysis. The study included 109 patients (218 hands). NCS-defined CTS was present in 34.1% of hands and in 44.0% of patients, indicating a substantial burden of objective neuropathy in SSc. Independent associations were predominantly traditional vascular and occupational factors, particularly arterial hypertension and smoking, whereas global SSc phenotype variables were not independently associated. Median nerve maxCSA showed moderate discriminative ability (AUC 0.722) with an optimal cutoff of 10 mm². Threshold-based definitions demonstrated increasing specificity with higher cutoffs. Although sensitivity remained limited, a positive ultrasound was substantially associated with the presence of CTS. CTS is common in SSc when systematically investigated and appears to be associated with general vascular vulnerability than with global disease phenotype. Ultrasound provides clinically meaningful complementary information, particularly as a confirmation and triage tool, and performs best in more advanced disease. While NCS remains important for exclusion and severity staging, ultrasound may help triage and support diagnosis in selected high-probability cases.