Correlations between the trigeminal nerve microstructural changes and the trigeminal-pontine angle features

Morphological and microstructural changes of the trigeminal nerve due to neurovascular compression (NVC) have been reported in primary trigeminal neuralgia (PTN) patients. This investigation was to examine the relationship between the trigeminal-pontine angle and nerve microstructural changes.

Twenty-five patients underwent microvascular decompression (MVD) for trigeminal neuralgia, and 25 age- and sex-matched controls were studied. The two groups underwent high-resolution three-dimensional MRI and diffusion tensor imaging (DTI). Bilateral trigeminal-pontine angle, cross-sectional area of cerebellopontine angle (CPA) cistern, and the length of trigeminal nerve were evaluated. The mean values of fractional anisotropy and apparent diffusion coefficient at the site of NVC were also measured. Correlation analyses were performed for the trigeminal-pontine angle and the diffusion metrics (FA and ADC) in PTN patients.

The mean trigeminal-pontine angle and FA value on the affected side was significantly smaller than the unaffected side and the control group (p < 0.001), while the mean ADC value was significantly increased (p < 0.01). When taking the conflicting vessel types into consideration, the angle affected by the superior cerebellar artery (SCA) was statistically sharper than when affected by other vessels (p < 0.01). However, there were no significant changes in the area of the CPA cistern or the length of the trigeminal nerve between the groups. Correlation analyses showed that the trigeminal-pontine angle was positively correlated with FA and negatively correlated with ADC.

A sharp trigeminal-pontine angle may increase the chance of NVC and exacerbate nerve degeneration, which may be one of the supplementary factors that contribute to the pathogenesis of trigeminal neuralgia.