Limbic grey matter alterations in patients with trigeminal neuralgia

Objective: Trigeminal neuralgia (TN) is a chronic disorder characterized by sudden shock-like pain of the face. A prior study showed gray matter (GM) abnormalities in TN patients in areas associated with pain perception and emotion, such as the thalamus and amygdala (DeSouza et al, 2013). We aimed to explore possible changes to other major limbic, or affect-related, areas including hippocampus, nucleus accumbens, insula, and cingulate. Methods: 47 patients and 62 healthy people were scanned using a 3T GE Signa HDx MRI scanner and an 8-channel head coil were used to acquire T1-weighted 3D FSPGR images. Freesurfer software (v. 4.5.0) was used for brain imaging, and SPSS for statistical, analyses (v. 22). Results were corrected for multiple comparisons (p < 0.05). Results: Patients and controls differed significantly in GM volumes in all areas of the affective circuitry studied (i.e. hippocampus, accumbens, insula, and mid and posterior cingulate). Unilateral differences were noted for patients with right- (R: 2067 mm3; L: 2681 mm3) vs. left- (R: 2009 mm3; L: 2296 mm3) sided pain in the rostral anterior cingulate compared to controls (R: 2228 mm3; L: 2740 mm3). There were no differences noted for the isthmus of the cingulate. Conclusion: Decreased GM volume was noted throughout affect-related circuits, with rostral anterior cingulate changes possibly related to the side of pain. These changes could reflect the negative affective experiences and brain function commonly associated with chronic pain sufferers and may be used in future to assist in clinical prognosis.