Direct Localization of the VIM/DRTT Using Quantitative Susceptibility Mapping in Essential Tremor: A Pilot MRI Study

Area of Science:

• Neuroimaging
• Neurosurgery
• Medical Physics

Background:

• Accurate localization of the ventral intermediate nucleus (VIM) within the dentatorubrothalamic tract (DRTT) is crucial for essential tremor (ET) neurosurgical treatment.
• Conventional diffusion tractography has limitations in direct VIM/DRTT visualization.

Purpose of the Study:

• To evaluate quantitative susceptibility mapping (QSM) for direct VIM/DRTT visualization.
• To assess the anatomical specificity of QSM for VIM/DRTT compared to diffusion tractography.

Main Methods:

• Twenty-seven participants (10 healthy, 17 ET patients) underwent 3T MRI.
• QSM and diffusion tractography were used to identify and reconstruct VIM/DRTT, pyramidal tract (PT), and medial lemniscus (ML) tracts.
• Spatial overlap between QSM- and tractography-defined regions was calculated to assess accuracy and specificity.

Main Results:

• QSM demonstrated high spatial correspondence with tractography-defined VIM/DRTT in healthy controls (85-88%) and ET patients (71-85%).
• Minimal overlap (<3.3%) was observed between QSM-defined VIM/DRTT and neighboring PT/ML tracts, confirming high anatomical specificity.
• Two participants were excluded due to insufficient tractography streamlines.

Conclusions:

• QSM enables direct visualization of the VIM/DRTT with high agreement to conventional tractography.
• QSM shows minimal overlap with adjacent tracts, confirming its anatomical specificity.
• QSM is a promising imaging modality for improved, patient-specific neurosurgical targeting in ET.