Ultra-high field brain MRI for functional neurological disorder: opportunities and challenges.

Functional neurological disorder (FND) is a common condition with debilitating neurological symptoms emerging from brain network alterations; yet, neuroimaging findings are often of unclear neurobiological significance. Contemporary mechanistic accounts indicate disturbances in hierarchical brain processing involving arousal, interoception, salience attribution, affective-motor integration, and self-agency. The findings of abnormal brain function with only partially consistent neuroimaging abnormalities imply that relevant pathology may occur below the resolution or contrast capabilities of conventional clinical MRI. Ultra-high field MRI (UHF, 7T and above) provides substantially improved spatial resolution, contrast sensitivity, and physiological specificity needed to interrogate microcircuit-, mesoscale-, and neurochemical-level mechanisms. We review how UHF-enhanced structural, diffusion, functional, and spectroscopic techniques can address long-standing mechanistic questions in FND. Selected targets that operate at different spatial scales are used to illustrate how UHF MRI can resolve features that are either inaccessible or not fully reliable at standard magnetic field strengths (1.5-3T). To synthesize these advances, we propose a biophysical multimodal MRI framework that integrates quantitative MRI, diffusion MRI, functional MRI, and MR spectroscopy to derive biologically interpretable markers spanning microstructure, white matter architecture, circuit dynamics, and neurometabolic domains. This approach aligns with contemporary computational and neurobiological models of FND and offers a scalable roadmap for future research. Together, UHF MRI and biophysically grounded multimodal imaging can enable a new generation of mechanistic studies in FND, with potential implications for diagnosis, subtype stratification, and biomarker development.