Structural And Functional Abnormalities Of Trigeminal Neuralgia: A Multimodal Magnetic Resonance Imaging Analysis

Trigeminal neuralgia(TN)is a chronic neuropathic pain disorder characterized by severe paroxysms of recurrent,paroxysmal,electric,shock-like,burn-like,intense pain limited to one or more divisions of the trigeminal nerve Increasing evidence suggests that TN is accompanied by abnormalities in brain morphology,white matter microstructure and function.However,whether these abnormalities are linked or reflect independent etiologies remains unknown.Using multimodal magnetic resonance imaging data of 20 TN patients and 21 healthy controls(HC),we investigated cortical gyrification abnormalities,their relationships with abnormalities of the underlying white matter microstructure and gray matter morphology,as well as their functional significance in TN.Based on the view of functional integration,we analyzed the topological properties of the brain functional networks of patients with TN.Compared with controls,TN patients showed significant local gyrification index(LGI)reductions predominantly in the left insular cortex,which were negatively correlated with pain intensity.In this cluster,TN patients had concurrent cortical thickness reductions but unaltered cortical surface area,and LGI of this cluster was not correlated with overlying cortical thickness or surface area.Meanwhile,TN patients had reduced FA in two white matter clusters of the fiber tracts that pass through the region of decreased LGI,and insular LGI was positively correlated with the fractional anisotropy(FA)of these two nearby white matter clusters.These results of correlation analysis suggesting that insular LGI reductions may be primarily driven by microstructural abnormalities of the underlying white matter tracts,rather than by abnormalities in cortical thickness and surface area.In addition,TN patients exhibited increased insula functional connectivity(FC)to the left posterior cingulate cortex and thalamus,which was positively correlated with disease duration.Finally,the functional connectivity networks of the healthy controls and TN patients all showed "small-world" properties,and the topological properties of the global network did not have obvious differences between groups.Whereas,the topological proporties of the local network such as node degree,node betweenness centrality,node clustering coefficient,and node local efficiency were significant differences between the groups in the left posterior cingulate cortex,right hippocampus,right parahippocampal gyrus,bilateral cuneus,left superior temporal gyrus,right postcentral gyrus and left supplementary motor area.These findings provide new evidence for the involvement of structural and functional abnormalities in the pathophysiology of TN.