Peripheral/central neural microstructural alterations in persistent idiopathic dentoalveolar pain: a case-comparative...

Persistent idiopathic dentoalveolar pain (PIDAP) has been considered to involve the predominant peripheral or central nervous system, but details of mechanisms remain unclear. This study investigated differences in clinical characteristics and microstructural integrity at the peripheral trigeminal nerve and central white matter between patients with PIDAP, depending on the presence or absence of neurovascular compression (NVC) at the root entry zone (REZ). This retrospective case-comparative study enrolled patients with PIDAP who underwent diffusion tensor imaging to evaluate neural integrity by fractional anisotropy (FA). FA of the trigeminal nerve at the REZ was assessed as a peripheral interaction, and FA in the white matter was assessed as a central interaction. Among 27 patients with NVC and 39 without NVC, pain intensity was significantly higher in patients without NVC (44.3 ± 27.5; 58.6 ± 25.4; p = 0.024). While patients with NVC showed significant FA reduction in the trigeminal nerve, patients without NVC showed a tendency toward FA reduction in the white matter. Right- and left-asymmetric FA patterns were detected in pain-related brain regions regardless of the presence of NVC. Somatic symptoms scale-8 (SSS-8) scores were negatively correlated with FA in the white matter in patients with NVC, whereas in patients without NVC, FA in pain-related brain regions was positively correlated with clinical characteristics: pain intensity, pain catastrophizing scales, and SSS-8 scores. These results suggest that PIDAP may have subgroups with peripheral- or central-predominant mechanisms, depending on the presence of NVC. While PIDAP with NVC may relate to FA reduction in the peripheral trigeminal nerve at REZ and the central microstructural alterations related to somatic symptom burden, PIDAP without NVC may be associated with FA alterations in pain-related brain regions, relating to pain severity, without peripheral neural alterations. Although further investigations are required, asymmetric FA patterns in certain pain-related brain regions could be specific features of PIDAP, regardless of the presence of NVC.