Can ultrasonography detect subclinical involvement of median and ulnar nerves in patients with rheumatoid arthritis?

The prevalence of subclinical neuropathy in Rheumatoid Arthritis (RA) is %65-85. It has been shown that RA patients may have electrophysiological or histological abnormalities even in the absence of clinical symptoms or signs of peripheral nevre involvement. The aim of this study is to determine whether median cross-sectional area (m-CSA) and ulnar CSA (u-CSA) at wrist level differ between RA patients without signs and symptoms of median and ulnar neuropathy and healthy controls. To achieve a difference of 2,8 mm² in CSA measures between RA patients and controls with an alpha error of 0,05 and %80 power, we planned to enroll 38 subjects in each group. Thirty-eight RA patients without signs and symptoms of median and ulnar neuropathy and 38 healthy controls were enrolled into study. All patients were included in ultrasonographic assessment (General Electric Logiq P5, 8-12 MHz high frequency transducer). M-CSA and u-CSA were measured at the proximal inlet of the carpal tunnel using the pisiform bone as landmark. There was no significant difference in m-CSA and u-CSA measures between RA patients and controls. There was no significant correlation between CSA measures of dominant hand and patient characteristics (age, height, weight, disease duration). In %24 of patients and %14 of controls m-CSA was above 10 mm². The difference was not statistically significant (p=0,20). We found similar ultrasonographic m-CSA and u-CSA values in RA patients and healthy controls. Nonetheless, these results can not exclude subclinical neurological involvement in RA patients without signs and symptoms of median and ulnar neuropathy.