Anatomical and Technical Reappraisal of the Pallidothalamic Tractotomy With the Incisionless Transcranial MR-Guided Focused Ultrasound. A Technical Note.

Marc N Gallay,Daniel Jeanmonod,Christian Federau,David Moser

doi:10.3389/fsurg.2019.00002

Abstract

Background: MR-guided focused ultrasound (MRgFUS) offers new perspectives for safe and efficient lesioning inside the brain. The issue of target coverage remains primordial and sub-optimally addressed or solved in the field of functional neurosurgery.Objective: To provide an optimized planning and operative strategy to perform a pallidothalamic tractotomy (PTT) in chronic therapy-resistant Parkinson's disease (PD) with the technology of MRgFUS.Methods and results: Histological sections and maps from 6 human brain hemispheres were analyzed and outlines of the pallidothalamic tract on Myelin-stained sections were drawn and superimposed. We determined a standardized PTT target coverage characterized by 5 to 7 preplanned target lesion sub-units of 1.5 × 1.5 × 3.0 mm, which were placed using focal point displacements and shortest possible times, under thermal dose control.Conclusion: We hereby present our current approach to the MRgFUS PTT on the basis of a histological reappraisal and optimized heat application to the pallidothalamic tract in the H1 field of Forel.

Highlights

A detailed localization analysis of the pallidothalamic tract in the subthalamic area was performed on the extensive original material accumulated by Dr Morel, partly published in different versions of the Morel’s Atlas of the human thalamus and basal ganglia [25,26,27] and in a fiber tract study [24]
Histological sections and maps from 6 human brain hemispheres (Morel’s cases Hb1-Hb5 and Hb8) cut in their axial stereotactic plane were superimposed [1] at their intercommissural plane (DV0) for distances between the center of the anterior (AC) and posterior (PC) commissures with an AC-PC distance ≥26 mm, and [2] at level V0.9 mm for AC-PC distances
Superposition was made on the mid-commissural line (MCL) [perpendicular line crossing the mid-point of the intercommissural line (ICL), see Figures 1–3] anteroposteriorly and on the mammillothalamic tract (MTT) in the mediolateral direction

Summary

Introduction

Since the advent of MRgFUS in functional neurosurgery [1], clinical experience has been gained by different groups worldwide in the fields of essential and parkinsonian tremor [2,3,4,5,6,7,8,9,10,11,12,13], obsessive compulsive disease [14], neurogenic pain [1, 15] and PD [16,17,18]. Optimal target volume coverage is the subject of this technical note. MR-guided focused ultrasound (MRgFUS) offers new perspectives for safe and efficient lesioning inside the brain. The issue of target coverage remains primordial and sub-optimally addressed or solved in the field of functional neurosurgery

Results

Discussion

Conclusion