Diffusion-weighted MR neurography of median and ulnar nerves in the wrist and palm

Objectives: To investigate the feasibility of diffusion-weighted magnetic resonance neurography (DW-MRN) in the visualisation of extremity nerves in the wrist and palm. Methods: Thirty-two volunteers and 21 patients underwent imaging of the wrist and palm on a 3-T MR scanner. In all subjects, two radiologists evaluated the image quality on DW-MRN using a four-point grading scale. Kappa statistics were obtained for inter-observer performance. In volunteers, the chi-squared test was used to assess the differences in nerve visualisation on DW-MRN and axial fat-suppressed proton density weighted imaging (FS-PDWI). Results: In volunteers, the mean image quality scores for the median nerve (MN) and ulnar nerve (UN) were 3.71 ± 0.46 and 3.23 ± 0.67 for observer 1, and 3.70 ± 0.46 and 3.22 ± 0.71 for observer 2, respectively. The inter-observer agreement was excellent (k = 0.843) and good (k = 0.788), respectively. DW-MRN provided significantly improved visualisations of the second and the third common palmar digital nerves and three branches of UN compared with FS-PDWI (P < 0.05). In patients, the mean image quality scores for the two observers were 3.24 ± 0.62 and 3.10 ± 0.83, inter-observer performance was excellent (k = 0.842). Conclusions: DW-MRN is feasible for improved visualisation of extremity nerves and their lesions in the wrist and palm with adequate image quality, thereby providing a supplementary method to conventional MR imaging. Key points: • DW-MRN provides adequate image quality for wrist and palm neurography • DW-MRN performs similarly to FS-PDWI in nerve visualisation at the wrist • DW-MRN provides improved visualisation of small nerves in the palm • DW-MRN serves as a supplementary method to evaluate peripheral neuropathies.