Vascular compression of the trigeminal nerve in asymptomatic individuals: a voxel-wise analysis of axial and radial diffusivity.

BACKGROUND: Neurovascular compression (NVC) of the trigeminal nerve is associated with trigeminal neuralgia (TN), but also occurs in many asymptomatic individuals. The purpose of this study was to investigate the possible microstructural tissue changes of trigeminal nerves (TGN) in asymptomatic individuals with NVC by using axial diffusivity (AD) and radial diffusivity (RD) of MR imaging and to discuss its underlying mechanisms. METHODS: Twenty asymptomatic individuals with unilateral NVC and 18 healthy controls (HCs) were divided into three groups (compressed, uncompressed side in asymptomatic individuals and HCs). Three groups were imaged with a 3.0-T MR system using three-dimensional fast imaging employing steady-state acquisition (3D FIESTA) and diffusion tensor imaging (DTI). We placed a region of interest over the root entry zone of the TGN and measured fractional anisotropy (FA), AD and RD. The mean values of FA, AD and RD were compared among the three groups. RESULTS: No significant changes in any of the diffusion metrics (FA, RD and AD) were found among the three groups (compressed, uncompressed side in asymptomatic individuals and HCs). CONCLUSIONS: Our study demonstrated that neither demyelination nor axonal injury is found in asymptomatic individuals with NVC.