Motor-related white matter tracts are prominently affected in primary trigeminal neuralgia

Primary trigeminal neuralgia (PTN) is a severe chronic pain disorder, yet whole-brain white matter microstructural alterations beyond the trigeminal nerve remain poorly understood, partly due to limitations of conventional diffusion tensor imaging in crossing fiber regions.

We prospectively enrolled 57 patients with classical PTN and 29 age‑ and sex-matched healthy controls. Seventy-two whole‑brain white matter tracts were reconstructed using constrained spherical deconvolution and fixel-based analysis. Fractional anisotropy (FA) was compared between groups using permutation testing with false discovery rate correction. Additional analyses examined associations with clinical variables, surgical outcomes, and neurovascular conflict status.

Six tracts showed significantly reduced FA in PTN patients compared to controls (all p < 0.05, FDR-corrected). All six belong to motor-related systems: right fronto-pontine tract, left corticospinal tract, and four striatal tracts (right striato-prefrontal, right striato-fronto-orbital, right striato-occipital, left striato-parietal). No significant correlations with pain severity or disease duration survived multiple comparisons.

Microstructural white matter alterations in PTN are not limited to sensory trigeminal pathways but prominently involve motor-associated striato-cortical and corticofugal projection tracts, suggesting that motor system reorganization may be one of the core features of PTN pathophysiology.