Frequency-specific alterations in cortical rhythms and functional connectivity in trigeminal neuralgia

Neuroimaging studies have shown that chronic pain is maladaptive and influences brain function and behavior by altering the flexible cerebral information flow. We utilized power spectral analysis to investigate the impact of classic trigeminal neuralgia (TN) on the oscillation dynamics of intrinsic brain activity in humans. The amplitude of low-frequency fluctuations (ALFF) and fractional ALFF (fALFF) were measured in 29 TN patients and 34 age- and sex-matched healthy controls (HCs) via resting-state functional MRI (R-fMRI). Two different frequency bands (slow-5: 0.01-0.027 Hz; slow-4: 0.027-0.073 Hz) were analyzed. Differences in blood oxygen level-dependent (BOLD) signal fluctuations and related resting-state functional connectivity (rsFC) between the TN patients and HCs were identified. The TN patients had reduced ALFF/fALFF in the posterior cingulate cortex (PCC), left insula, left dorsolateral prefrontal cortex (DLPFC), left putamen and bilateral temporal lobe, exclusively in the frequency of the slow-5 band. Whole brain rsFC analyses with these six different regions as seeds revealed two weaker circuits including the PCC-medial prefrontal cortex (mPFC) and DLPFC-hippocampus circuits, indicating abnormal interactions with the default mode network (DMN) in TN patients. The functional connectivity between the default-mode regions (mPFC and PCC) in the slow-5 band tracked pain intensity. Together, our results provide novel insights into how TN disturbs the cortical rhythms and functional interactions of the brain. These insights may have implications for the understanding and treatment of brain dysfunction in chronic pain patients, including TN patients.