Ultrasonography Shows Increased Cross-sectional Area of the Median Nerve in Patients with Arthritis and Carpal Tunnel Syndrome

Objectives: To examine whether patients with arthritic diseases and carpal tunnel syndrome (CTS) have increased cross-sectional areas of the median nerves measured by ultrasonography (US). Enlarged cross-sectional areas have previously been found in non-arthritic patients with idiopathic CTS.

Methods: During 1 yr, all 12 patients with rheumatoid arthritis (RA) or other arthritic diseases hospitalized in our department for surgery for CTS were included. Nine of the patients had bilateral CTS, giving a total of 21 pathological nerves. The median duration of CTS symptoms was 9.5 months. The controls were 30 randomly selected RA patients without symptoms of CTS and 30 healthy persons. Both CTS patients and controls were examined bilaterally by use of US at the entrance of the carpal tunnel, and the cross-sectional areas of the median nerves were calculated.

Results: Cross-sectional areas of the median nerves were significantly higher in the CTS patients compared with the RA controls and healthy persons; median (range) areas were 15.7 mm(2) (11.1-21.8), 8.5 mm(2) (5.8-11.0) and 8.0 mm(2) (4.9-12.0), respectively (P<0.0001). No significant differences in cross-sectional areas were observed between the two control groups, or between the right and left hand in the control groups.

Conclusions: Higher cross-sectional areas were found in the arthritic patients with CTS than in RA patients and healthy persons without CTS. This supports previous studies of idiopathic CTS in which increased cross-sectional areas have been found. Thus, as in idiopathic CTS, arthritic patients may be examined by US of the median nerve when CTS is suspected.