Connectivity derived thalamic segmentation in deep brain stimulation for tremor.

Area of Science:

• Neurosurgery
• Neuroimaging
• Neurology

Background:

• The ventral intermediate nucleus (VIM) is a key surgical target for treating tremor in Parkinson's disease (PD) and essential tremor (ET).
• Conventional MR imaging makes VIM identification difficult, necessitating indirect targeting and intraoperative awake confirmation due to individual anatomical variability.
• Accurate VIM and dentato-rubro-thalamic tract (DRT) localization is crucial for effective deep brain stimulation (DBS).

Purpose of the Study:

• To identify the VIM and DRT using probabilistic tractography in patients undergoing thalamic DBS for tremor.
• To evaluate the correlation between active DBS contact location, VIM-DRT connectivity, and treatment response.
• To assess the clinical feasibility of connectivity-based VIM segmentation.

Main Methods:

• High angular resolution diffusion imaging (HARDI) was performed preoperatively on nine patients (4 PD, 5 ET).
• Probabilistic tractography and parallel GPU processing were used to identify thalamic areas connected to motor cortex and contralateral dentate nucleus.
• Volume of tissue activation (VTA) from active DBS contacts was modeled and compared to segmented areas.

Main Results:

• Connectivity-based segmentation successfully identified thalamic areas corresponding to the VIM and the DRT.
• The DRT was visualized connecting the primary motor cortex to the contralateral dentate nucleus via the VIM.
• Patients with active DBS contacts within the VIM area showing high connectivity to the dentate nucleus exhibited better tremor reduction.

Conclusions:

• Probabilistic tractography provides accurate, individualized segmentation of the VIM and DRT for thalamic DBS targeting.
• Connectivity-based VIM segmentation is clinically feasible and improves targeting precision.
• This technique enhances the understanding of the cerebello-thalamo-cortical network in tremor.