Structural abnormalities of the trigeminal root revealed by diffusion tensor imaging in patients with trigeminal neuralgia caused by neurovascular compression: a prospective, double-blind, controlled study.

Because diffusion tensor imaging (DTI) is able to assess tissue integrity, we used diffusion to detect abnormalities in trigeminal nerves (TGN) in patients with trigeminal neuralgia (TN) caused by neurovascular compression (NVC). We also studied anatomical TGN parameters (cross-sectional area [CSA] and volume [V]). Using DTI sequencing in a 3-T magnetic resonance imaging (MRI) scanner, we measured the fraction of anisotropy (FA) and the apparent diffusion coefficient (ADC) of TGN in 10 patients selected as candidates to have microvascular decompression (MVD) for TN, and 6 normal control subjects. We compared data between the affected nerves of TN (ipsilateral TN), unaffected nerves of TN (contralateral TN), and both nerves in normal subjects (controls), and correlated these data with CSA and V. The FA of the ipsilateral TN (0.37±0.08) was significantly lower (P<.05) compared with the contralateral TN (0.48±0.08) and control values (0.52±0.04). The ADC of ipsilateral TN (5.6±0.89 mm(2)/s) was significantly higher (P<.05) compared with the contralateral TN (4.26±0.59 mm(2)/s) and control values (3.84±0.43 mm(2)/s). Ipsilateral TN had less V and CSA compared with contralateral TN and control values (P<.05). The Spearman correlation coefficient showed a strong positive correlation between loss of FA and loss of V (r=0.7576) and loss of CSA (r=0.9273) of affected nerves. The Spearman correlation coefficient showed a strong negative correlation between increase in ADC and loss of V (r=-0.7173) and loss of CSA (r=-0.7416) in affected nerves. DTI revealed alteration in the FA and ADC values of the affected TGN. These alterations were correlated with atrophic changes in patients with TN caused by NVC.