To discuss the alterations of functional brain properties in patients with idiopathic trigeminal neuralgia (ITN) based on graph theoretical approaches.

A total of 20 patients with pain in the distribution of left trigeminal nerve and 22 matched healthy controls were recruited in our hospital from May 2013 to January 2015. Resting-state functional MRI data in both groups were collected and analyzed with GRETNA software to obtain the matrices of brain network. From these connectivity matrices, a number of key characteristics were computed, including network efficiency, weighted shortest path length, weighted clustering coefficient and small-wordless. A two-tailed t test was used to appraise the significance of any inter-group differences in complex network measures investigated. Network-based statistic (NBS) approach was used to localize specific pairs of brain regions in which functional connectivity strength were altered in patients. Pearson's correlation analyses were performed to identify the correlations between clinical data and altered network properties in patients.

ITN patients had significantly increased weighted clustering coefficient in the right calcarine (CAL) and bilateral thalamus, increased total efficiency in the left superior frontal gyrus (SFG), and increased regional efficiency in the right SFG, right CAL, bilateral cuneus and left pallidum, and significantly reduced weighted shortest path length for regional nodal characteristics in the right superior parietalis lobules (P<0.05). The total efficiency in the left SFG and regional efficiency in the right SFG in ITN patients were negatively correlated with course of disease (r=-0.500, P=0.035; r=-0.501, P=0.034). As compared with the healthy controls, the ITN patients had enhanced functional loop connection between left SFG and right supplementary motor area, between left SFG and right SFG, between left SFG and right middle frontal gyrus, between left SFG and right orbital middle frontal gyrus, between left SFG and partes opercularis of right gyrus frontalis inferior (IFGoperc), between left SFG and bilateral putamen (PUT), between left SFG and right PAL, between right PUT and left interior superior frontal gyrus, and between left PUT and right caudate nucleus. The connectivity strength between left SFG and right IFGoperc was negatively correlated with disease duration (r=-0.487, P=0.041).

Alterations in regional nodal characteristics may suggest central sensitization and modulation in ITN patients.

Idiopathic trigeminal neuralgia; Graph theory; Resting-state functional magnetic resonance imaging; Brain network