Diffusion tensor imaging of mild-moderate carpal tunnel syndrome: correlation with nerve conduction study and clinical tests

The purpose of this study was to assess diffusion tensor imaging in the diagnosis of mild-moderate carpal tunnel syndrome (CTS) and to correlate fractional anisotropy (FA) and apparent diffusion coefficient (ADC) with nerve conduction study and clinical tests. This prospective study was conducted upon 39 patients (9 males, 30 females; mean age = 33 years) with early stage of CTS. Twenty age- and sex-matched healthy volunteers were included as a control group. All patients underwent clinical tests and nerve conduction studies with calculation of the distal motor latency (DML) and distal sensory latency (DSL). Patients with CTS and volunteers underwent diffusion tensor imaging of the median nerve. The cross-sectional area (CSA), FA, and ADC of the median nerve were calculated. There was significant difference in FA and ADC between patients and controls (P = 0.001 respectively) and between mild and moderate CTS (P = 0.001 respectively). The cutoff FA and ADC of the median nerve used for the diagnosis of CTS were 0.45 and 1.31 × 10^-3 mm²/s with areas under the curve (AUC) of 0.985 and 0.954, respectively, and the values used to differentiate mild from moderate CTS were 0.42 and 1.35 × 10^-3 mm²/s with AUC of 0.964 and 0.688, respectively. The FA and ADC of the median nerve were correlated with CSA (r = 0.894; -0.769), DML (r = -0.935; 0.781), DSL (r = -0.953; 0.781), Tinel's test (r = 0.742; 0.684), and Phalen's test (r = 0.862; 0.742). Diffusion tensor imaging can be used for the diagnosis of mild-moderate CTS and well correlated with nerve conduction studies and clinical tests.