Metabolic alterations in patients with essential tremor before and after deep brain stimulation: Keys to understanding tremor using magnetic resonance spectroscopy

Nathanael Goransson^1,2Sofie Tapper¹Peter Lundberg^3,4Peter Zsigmond^2*Anders Tisell^3,4

• ¹Department of Biomedical Engineering, Linköping University, Linköping, Sweden, Linköping, Sweden
• ²Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
• ³Department of Medical Radiation Physics and Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden, Linköping, Sweden
• ⁴Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden, Linköping, Sweden

The pathophysiology behind EssenAal Tremor (ET) and the mechanism behind the clinical effect ader Deep Brain SAmulaAon (DBS) is not fully understood. This arAcle aims to increase the understanding of ET pathophysiology and the mechanisms behind DBS using MagneAc Resonance Spectroscopy ( 1 H-MRS). PaAents with ET underwent MRS scans of the cerebellum and thalamus before and ader DBS, and the results were compared to a healthy control group.Ten ET paAents and seven healthy controls were included. PreoperaAvely and approximately five months postoperaAvely, single-voxel MRS was performed on a 1.5 T (tesla) system. Voxels were placed in the thalamus (14 x 13 x 13 mm 3 ), dentate nucleus (13 x 13 x 13 mm 3 ) and cerebellar cortex (13 x 13 x 13 mm 3 ). Metabolite concentraAons of total N-acetylaspartate + N-acetyl-aspartyl-glutamate (tNA), total creaAne + phosphocreaAne (tCr), total choline + phosphocholine + glycerophosphocholine (tCho), and total glutamate and glutamine, which together consAtute Glx were quanAfied. The paAents were evaluated with Essen/al Tremor Ra/ng Scale (ETRS) preoperaAvely and postopera-Avely.A total of 14 leads were implanted, and ETRS scores improved significantly following surgery. Thalamic tNA concentraAons reduced significantly within the paAent group ader surgery, as well as in comparison to healthy control values. The significant difference in tNA concentraAon following surgery was observed only in the thalamus that had been targeted with a lead, not elsewhere. No addiAonal differences in metabolite concentraAons (tCr, tCho, Glx) were observed in the thalamic voxel, and none of the studied metabolites (tNA, tCr, tCho, Glx) showed detectable differences in the cerebellar voxels (dentate nucleus and cerebellar cortex).In a highly selected paAent group affected by ET, we present novel metabolite informaAon using MRS. Specifically, a reduced thalamic tNA concentraAon was observed on the lead-implanted side following DBS, suggesAng a possible treatment effect. !