Temporal muscle thickness on brain MRI as a surrogate marker of sarcopenia and treatment response in tremor patients undergoing MRgFUS thalamotomy.

BackgroundReduced Temporal Muscle Thickness (TMT) has been proposed as a marker of sarcopenia in Parkinson's Disease (PD) and Essential Tremor (ET). This study aimed to assess TMT measured on brain MRI in PD and ET patients undergoing unilateral Vim thalamotomy with MR-guided Focused Ultrasound (MRgFUS).MethodsThis retrospective single-center study (2019-2023) included patients with tremor-dominant PD or ET refractory to medical therapy. Demographic data, disease duration, and tremor severity (Fahn-Tolosa-Marin scale) were collected. Brain MRI and clinical evaluations were performed at baseline and during follow-up (1 month, 6 months, 1 year, and 2 years). TMT was manually measured on axial T1-weighted MR images. Statistical analyses evaluated differences and correlations between TMT and clinical variables.ResultsA total of 165 patients (69 PD, 96 ET) were analyzed. Disease duration was longer in ET patients (p < 0.001), with no significant age difference. TMT did not differ significantly between PD and ET groups (p = 0.08). In ET patients, TMT correlated nega-tively with age (r = -0.24, p = 0.03), while no correlation was found in PD patients. At 2 year follow-up, TMT negatively correlated with tremor reduction in both PD (r = -0.42, p = 0.03) and ET (r = -0.34, p = 0.05) groups.ConclusionsIn our series, no significant differences emerged between ET and PD patients regarding TMT status as a surrogate marker of sarcopenia. Lower TMT may be associated with worse tremor outcomes after MRgFUS thalamotomy and could serve as a supportive imaging biomarker in patient assessment for tremor treatment.