Technical advances in ultrasound and MR imaging of carpal tunnel syndrome

The aim of this study was to compare the latest ultrasound-array technology to a conventional “high-resolution” transducer, modified MRI technique, and nerve conduction studies (NCS), in the diagnosis of carpal tunnel syndrome (CTS). In 19 normal wrists and 15 wrists with CTS, US with two different transducers was performed: a conventional linear-array transducer (LA) and a newly developed Multi-D linear-array transducer (MDA) were used. The US images were evaluated determining the swelling and the flattening ratios of the median nerve and correlated to respective findings in MRI (1.5 T) and to NCS. The NCS confirmed CTS in all 15 wrists. Measures of median nerve compression (swelling and flattening ratios) were significantly different in patients with CTS and controls (p < 0.01) with both types of US transducers and MRI. The MDA yielded higher correlation to MRI than the LA. Using critical values of 1.3 for the swelling and 3.4 for the flattening ratio, MRI, and US with the MDA yielded a sensitivity of 100 % each. Modern imaging modalities allow for an exact diagnosis of CTS even in cases with only slight median nerve pathology.