Microstructural, Morphological, and Metabolic Changes Following Magnetic Resonance-Guided Focused Ultrasound...

Area of Science:

• Neurosurgery
• Neuroradiology
• Psychiatry

Background:

• Magnetic resonance-guided focused ultrasound capsulotomy (MRgFUS-AC) is an experimental incisionless treatment for obsessive-compulsive disorder (OCD) and major depressive disorder (MDD).
• While MRgFUS-AC shows clinical efficacy, its long-term effects on brain structure and microstructural integrity are not fully understood.

Purpose of the Study:

• To investigate the longitudinal structural and microstructural brain changes induced by MRgFUS-AC in patients with treatment-resistant OCD and MDD.
• To correlate preoperative imaging features with clinical outcomes.

Main Methods:

• 33 patients (14 OCD, 19 MDD) underwent MRgFUS-AC targeting the ventral anterior limb of the internal capsule (ALIC).
• Diffusion and structural MRI were acquired pre- and post-operatively.
• Probabilistic tractography assessed white matter integrity; FreeSurfer quantified cortical and subcortical volumes.

Main Results:

• MRgFUS-AC created small lesions that regressed significantly within three months.
• Reductions in fractional anisotropy were observed in cortico-thalamic and cortico-striatal tracts.
• Volume loss occurred in cortical (medial orbitofrontal, inferior temporal, fusiform) and subcortical (caudate) regions, with greater impact in OCD patients. Smaller left pars triangularis volume predicted better clinical improvement.

Conclusions:

• MRgFUS-AC induces measurable white and gray matter changes in fronto-striatal-thalamic circuits, even with small, regressing lesions.
• Structural alterations were more pronounced in OCD compared to MDD.
• Preoperative imaging may help personalize targeting strategies for psychiatric neurosurgery.