Ventralis intermedius nucleus anatomical variability assessment by MRI structural connectivity.

Area of Science:

• Neuroimaging
• Neurosurgery
• Human Anatomy

Background:

• The ventralis intermedius nucleus (Vim) is a key surgical target for refractory tremor, located within the dentato-thalamo-cortical pathway (DTCp).
• Conventional MRI cannot visualize the Vim, leading to reliance on atlas-based coordinates for stereotactic targeting.
• This atlas-based approach overlooks individual anatomical variations, potentially impacting long-term surgical efficacy.

Purpose of the Study:

• To identify the connectivity-defined Vim (cd-Vim) in vivo using probabilistic tractography of the DTCp.
• To quantify the variability of cd-Vim location across a healthy population.
• To compare cd-Vim coordinates with atlas-defined Vim (ad-Vim) and assess methodological confounds.

Main Methods:

• Probabilistic tractography was used to reconstruct the DTCp in 100 healthy individuals from the Human Connectome Project.
• The connectivity-defined Vim (cd-Vim) was identified based on DTCp reconstruction.
• The influence of potential methodological confounds on cd-Vim localization was assessed.

Main Results:

• No significant effect of methodological confounds on cd-Vim location was found.
• The mean cd-Vim coordinates differed from ad-Vim coordinates by 1.88–2.12 mm (midpoint) and 3.98–5.41 mm (ad-Vim).
• Greater variability in cd-Vim location was observed on the right side, potentially due to hemispheric asymmetries.

Conclusions:

• Significant individual anatomical variability of the cd-Vim exists, which is not captured by current atlas-based targeting methods.
• Tractography-based methods can identify this variability, offering potential for improved surgical targeting.
• These findings may lead to enhanced efficacy and reduced side-effects in thalamic surgery for tremor.