Prognostic implications of microstructural changes in patients with idiopathic trigeminal neuralgia

Abstract A variety of biomarkers other than degree of neurovascular compression have been used to estimate the likelihood of long-term pain-freedom after microvascular decompression (MVD). In this study, we report the prognostic implications of microstructural changes found in patients with idiopathic trigeminal neuralgia (iTN) with an arterial contact without morphological changes. Patients 18 years or older who underwent MVD as their initial surgical procedure for iTN with arterial contact without morphological changes between March 2013 and December 2021 were analyzed. Mean diffusivity, radial diffusivity, axial diffusivity, and fractional anisotropy (MD, RD, AD, and FA) were extracted from the cisternal segment of the trigeminal nerve immediately adjacent to the root entry point. Metrics were compared between symptomatic and asymptomatic trigeminal nerves. Metrics from the symptomatic trigeminal nerve were compared between responders and nonresponders to MVD. To avoid false discovery of a significant P -value, we used the Bonferroni correction method. A statistical significance criterion of q < 0.05 was used. When comparing the symptomatic trigeminal nerve with the asymptomatic trigeminal nerve, the MD was significantly increased on the symptomatic side (q = 0.00047), the RD was significantly increased on the symptomatic side (q = 0.0000066), and the FA was significantly decreased on the symptomatic side (q = 0.0000054). Fractional anisotropy was significantly decreased in nonresponders (q = 0.0056). Fractional anisotropy has potential to preoperatively identify patients with iTN with arterial contact without morphological changes that will respond to MVD. This study identifies a subset of patients with iTN who are not truly “idiopathic.”