g_zur@rambam.health.gov.il

We aim to explore the impact of MRgFUS treatment functional connectivity nd white matter integrity in tremor-related circuits and test whether tremor improvement is correlated to specific pre- or post-treatment functional responsese.

60 patients with either essential tremor or Parkinson's disease underwent tremor and quality-of-life assessments prior to and at one and six months following focused ultrasound ablation. 21 patients underwent MRI including T1, T2-Flair and resting-state fMRI before treatment and at one day, 7-10 days, 1-3 months, and 4-12 months following it. 39 patients underwent MRI including T1, T2-Flair and diffusion tensor weighted imaging before treatment and at similiar time points to the fMRI group. Diffusivity parameters were calculated and fiber tractography measures were extracted. Changes in functional connectivity and in diffusivity parameters were assessed in different brain areas that are related to tremor.

Decreased functional connectivity was found between the dentate nucleus and the motor thalamus following ablation. Long term damage, was found in the ablated core and in the tract connecting the thalamus and red-nucleus. Inverse correlation was found between fractional anisotropy in the motor thalamus one day following ablation and tremor improvement in both patient groups, with lower values before treatment associated with better outcome (tremor relief) in essential tremor patients.

long-term changes in functional connectivity and white matter integrity are present following focused ultrasound thalamotomy. Regions demonstrating long-term white matter changes may be responsible for the tremor relief seen in patients, implicating these regions in the disorder's pathogenesis.

The expected findings of this project would ultimately aid in more accurate patient selection for thalamotomy, as well as assist in further development of ET tremor treatments.