Thalamic nuclei in patients with chronic facial pain: gray matter volume patterns before and after surgery

Trigeminal neuralgia is a prevalent chronic pain disorder characterized by recurring episodes of intense facial pain, which significantly impairs patients' quality of life. MRI-based biomarkers have consistently demonstrated their ability to predict pain intensity and treatment outcomes. However, most studies have primarily focused on the trigeminal system, paying less attention to the extensive neural reorganization that occurs throughout the brain in response to chronic pain. In this study, we aimed to examine the thalamus, a key brain structure involved in information processing, and provide a detailed perspective on thalamic remodeling in response to chronic pain at the level of individual thalamic nuclei. We analyzed a sample of 62 patients with primary trigeminal neuralgia undergoing surgical treatment, along with 28 healthy participants. Our results revealed significant gray matter volume changes in thalamic nuclei among patients with trigeminal neuralgia. Notably, the intralaminar nuclei (centromedian/parafascicular) and nuclei associated with visual and auditory signal processing (lateral and medial geniculate bodies) exhibited significant alterations, contrasting with the ventral group nuclei involved in nociceptive processing. Additionally, we found no substantial volume increase in any of the studied nuclei following successful surgical intervention 6 months later. The volumes of thalamic nuclei were negatively correlated with pain intensity and disease duration. The findings obtained in this study, albeit preliminary, have promising clinical implications as they unveil previously unknown facets of chronic pain development. Perspective. The study examined alterations in gray matter volume within the thalamus of patients diagnosed with trigeminal neuralgia at the level of specific nuclei. The most significant changes were observed in the lateral and medial geniculate bodies, along with the pulvinar nuclei.