Diffusion tensor imaging of the median nerve in recurrent carpal tunnel syndrome - initial experience.

OBJECTIVES: To investigate median nerve structure in patients with recurrent carpal tunnel syndrome (CTS) using diffusion tensor imaging (DTI) and to relate DTI changes to anatomical MRI and to measures of median nerve function.
METHODS: Median nerve structure was quantified according to DTI in patients with recurrent CTS and in healthy controls of similar age. Anatomical MRI was used to identify the presence of nerve compression and fibrosis. Median nerve function was measured using electromyography, a force-tracking task (accuracy of precision grip control) and clinical measures.
RESULTS: Patients showed reduced apparent diffusion coefficient (ADC), reduced axial diffusivity (AD) and radial diffusivity (RD) along the median nerve compared with controls (P < 0.001). Patients with endoneural fibrosis had the greatest reductions in ADC and in RD. ADC and AD correlated positively with nerve conduction velocity (R = 0.54 and R = 0.68, respectively) and fractional anisotropy correlated negatively with error during force-tracking (R = -0.58).
CONCLUSIONS: A specific pattern of DTI changes in the median nerve was identified in patients with recurrent CTS. Fibrosis may be underlying these structural changes. The correlations with nerve conduction velocity and accuracy of force control suggest that DTI is a promising technique in the study of median nerve structure in recurrent CTS. KEY POINTS: • Diffusion tensor imaging (DTI) offers further possibilities in musculoskeletal magnetic resonance imaging. • DTI reveals median nerve changes in recurrent carpal tunnel syndrome. • DTI changes were greater with signs of median nerve fibrosis. • DTI parameters correlated with nerve conduction and force control measures. • DTI is a promising technique in recurrent carpal tunnel syndrome.