Introduction : Trigeminal neuralgia (TN) is one of the most troublesome forms of neuropathic orofacial pain. However, its underlying mechanisms remain unclear and we lack data regarding the condition. Our objective was to investigate how grey matter volume (GMV) differed in two types of TN (classical trigeminal neuralgia, CTN, and painful post-traumatic trigeminal neuralgia, PPTN) compared with healthy controls (HC).

  Material and methods : Our participants included 30 CTN patients and 25 PPTN patients. We applied voxel-based morphometry (VBM) using 3T magnetic resonance imaging to compare GMV in CTN and PPTN with that in healthy controls, and also with one another. We performed a regression analysis to test whether GMV is related to clinical measures. A region of interest (ROI) analysis was conducted to correct for multiple comparisons.

  Results : We observed a significantly smaller GMV in the right inferior temporal gyrus of both CTN and PPTN patients compared with HC. In addition, a significant GMV deficit was found in the right middle temporal gyrus in PPTN patients compared with HC. We also observed a smaller GMV in PPTN compared with CTN in the temporal and parietal cortices. Pain duration was negatively correlated with GMV in PPTN patients.

  Conclusion : TN is associated with GMV changes in the temporal cortices, which suggests a potential role of these brain regions in the condition.

  Recent progress in gene mutation analysis has provided relevant information to understand the pathogenesis of oral cancer. Inactivating mutations of NOTCH1, an intercellular signaling receptor that regulates proliferation and differentiation, have been found commonly in squamous cell carcinomas including oral cancer. Although Notch1 is thought to be a tumor suppressor, its expression in oral tumors has not been thoroughly studied. This study was designed to determine the relationship between Notch1 and oral tumor developments, with particular emphasis on precancers. To induce tongue tumors, 4-nitroquinoline-1-oxide (4-NQO) was administered for 8 weeks to 6-week-old mice through the drinking water. Tongues were harvested at 28 weeks of age and histological analysis was performed. Multiple precancers and cancers developed in the 4-NQO-treated group. Immunohistological examination revealed that Notch1, which was expressed in basal cells, was decreased in most precancers. In addition, many histologically normal Notch1-negative areas (Notch1 (－) patches) were observed. Comparison analysis of tongue specimens harvested at 16, 20, and 24 weeks after the start of 4-NQO treatment suggested that Notch1 (－) patches occurred at the initial stage of tumorigenesis, and some progressed to precancers. The Notch1 (－) patches showed normal expression patterns of differentiation markers suggesting Notch1 is not essential for epithelial integrity. Examination of 20 human specimens indicated that the decrease of Notch1 expression can be used as a marker for precancers. In conclusion, downregulation of Notch1 is important in the initial stage of oral precancer development, which is in agreement with its putative tumor suppressor function.