Are there two different forms of functional dystonia? A multimodal brain structural MRI study

Area of Science:

• Neuroscience
• Neurology
• Radiology

Background:

• Functional dystonia (FD) is a movement disorder with distinct clinical presentations.
• Two phenotypes, typical fixed dystonia (FixFD) and the recently described mobile dystonia (MobFD), require differentiated investigation.
• Understanding the neural underpinnings of these FD variants is crucial for targeted interventions.

Purpose of the Study:

• To investigate and compare brain structural alterations in FixFD and MobFD using magnetic resonance imaging (MRI).
• To elucidate the neuroanatomical differences between the two FD phenotypes and healthy controls.

Main Methods:

• Recruited 44 FD patients (13 FixFD, 31 MobFD) and 43 healthy controls.
• Utilized 3D T1-weighted and diffusion tensor (DT) MRI for comprehensive brain analysis.
• Assessed cortical thickness, gray matter (GM) volumes, and white matter (WM) tract integrity.

Main Results:

• Both FD groups showed normal cortical thickness compared to controls.
• MobFD patients exhibited cortical thinning in orbitofrontal, parietal, and cingulate regions, along with reduced GM volumes in subcortical structures (nucleus accumbens, putamen, thalamus, caudate).
• FixFD patients displayed severe WM disconnection in the corpus callosum, corticospinal tract, and thalamic radiations, affecting sensorimotor and emotional circuits.

Conclusions:

• Distinct MRI patterns differentiate MobFD and FixFD.
• MobFD is associated with GM alterations in regions critical for sensorimotor, emotional, and cognitive control.
• FixFD is characterized by global WM disconnection, suggesting widespread network dysfunction.