Volumetric Assessment and Graph Theoretical Analysis of Thalamic Nuclei in Essential Tremor

Essential tremor (ET) is a neurological disorder primarily characterized by upper limb action tremor. It is widely recognized that the thalamus is implicated in ET pathophysiology, playing a central role in treatment approaches. This study aimed to explore thalamic morphology, assessing macrostructural changes and intrinsic thalamic networks in ET patients.

A total of 109 ET (41 with and 68 without resting tremor) and 81 healthy controls (HC) were enrolled in the study. An automatic probabilistic segmentation of thalamic nuclei was employed on T1-weighted MRI images using FreeSurfer 7.4. Subsequently, volumetric data were extracted, and graph theoretical analysis was applied on the cortical-thalamic nuclei network, assessing global and local network properties.

No significant differences were observed in the volume of thalamic nuclei between ET patients and HC. ET patients exhibited significant alterations in the global thalamic network, suggesting a less efficient brain network in comparison with HC. ET patients also showed local alterations of thalamic network such as lower eccentricity and path length in the ventral nuclei and reduced efficiency in the pulvinar, indicating a less interconnected network. No significant differences were observed between ET patients with and without rest tremor.

Our study demonstrates reduced global and local efficiency of brain networks in ET patients, suggesting impaired communication and interconnection between brain regions. These findings confirm the involvement of the ventral lateral and pulvinar nuclei as key regions in tremor pathophysiology in ET patients, supporting the targeting of these regions for therapeutic approaches.