Median nerve swelling in RA patients: an 8-year longitudinal MRI-based study

Rheumatoid arthritis (RA) patients are prone to carpal tunnel syndrome (CTS). MRI can accurately detect median nerve swelling associated with CTS as well as evaluate synovial inflammation and structural damage. A median nerve cross-sectional area (CSA) of > 15 mm² is the best MRI diagnostic criterion of CTS. This study investigates the prevalence of median nerve swelling in early RA patients, its relationship to inflammation and structural damage, and long-term outcome following treatment.

Retrospective study of early RA patients who underwent clinical, serology, radiography, and dynamic contrast-enhanced MRI of the wrist at baseline, year 1, and year 8. Median nerve cross-sectional area (CSA), median nerve enhancement and perfusion, retinacular bowing, synovial inflammation, structural damage and functional impairment were assessed.

81 early RA patients (age: 54 ± 13 years, F/M: 64/17) were studied. Undue median nerve swelling was present in 25 (31%) at baseline and 37 (46%) of 81 ERA patients at year 8. Undue median nerve swelling was moderately (r = 0.634) related to tenosynovitis volume at baseline but was otherwise not related to synovitis and structural damage at either baseline, year 1, or year 8. Median nerve swelling did not regress long-term. At year 8, CTS symptoms were present in about half of RA patients and were not related to median nerve swelling. Functional impairment at year 8 was more frequent in patients with median nerve swelling.

Undue median nerve swelling is common in RA patients, is not related to synovitis or structural damage, does not regress with treatment, and is linked to long-term functional impairment.

Median nerve swelling, indicative of carpal tunnel syndrome, is common in RA patients, does not regress with reduction in synovitis or tenosynovitis after treatment and is associated with more severe and more frequent systemic functional impairment.

Almost one-third of RA patients fulfilled MRI criteria for carpal tunnel syndrome (CTS) diagnosis at baseline, increasing to almost one-half of patients at year 8. Long-term median nerve swelling is not related to tenosynovitis, synovitis or structural damage. Functional impairment was over twice as common in patients with undue median nerve swelling than those without undue median nerve swelling.