Mapping the thalamic subnuclei in fibromyalgia: insights into pain modulation and affective amplification.

Fibromyalgia is a chronic disorder characterized by widespread pain, fatigue, sleep problems, and emotional or cognitive difficulties. The thalamus is central to both pain modulation and affective processing, yet structural alterations within its subregions remain unclear. This study examined volumetric characteristics of thalamic subnuclei in individuals with fibromyalgia and explored their relationships with clinical symptoms. Structural magnetic resonance imaging data from 20 female patients with fibromyalgia and 20 age and gender-matched healthy controls were analyzed using automated segmentation of 25 thalamic subnuclei per hemisphere. Volumes were normalized to total intracranial volume, and group differences were evaluated with multivariate analysis of covariance controlling for age. Correlation analyses were performed to assess associations between subnuclei volumes and clinical measures of pain intensity, anxiety, and pain-related thoughts. Although no significant group differences were observed after correction for multiple comparisons, positive associations emerged between disease duration and several medial and posterior thalamic nuclei. Greater volumes in these nuclei were also related to higher pain intensity and anxiety scores. These findings suggest that structural reorganization of specific thalamic regions may underlie both the sensory and emotional aspects of chronic pain. Further longitudinal and multimodal imaging studies are warranted to clarify the temporal dynamics and functional relevance of these thalamic alterations.