Globally altered microstructural properties and network topology in Rasmussen's encephalitis.

Area of Science:

• Neuroscience
• Neuroradiology
• Neuroimmunology

Background:

• Rasmussen's encephalitis is an immune-mediated brain disorder causing progressive unilateral cerebral atrophy, neuroinflammation, seizures, and cognitive decline.
• Contralateral hemisphere involvement, evidenced by volumetric changes and epileptiform activity, suggests a broader impact than initially understood.

Purpose of the Study:

• To investigate white matter integrity, structural network topology, and network efficiency in Rasmussen's encephalitis using diffusion-tensor imaging.
• To explore the extent and nature of brain network alterations in Rasmussen's encephalitis.

Main Methods:

• Diffusion-tensor imaging (DTI) and T1-weighted structural MRI were performed on 14 individuals with Rasmussen's encephalitis and 20 healthy controls.
• Fixel-based analysis quantified microstructural white matter integrity (fibre density and cross-section).
• Structural network models analyzed inter- and intrahemispheric connectivity and global efficiency.

Main Results:

• Individuals with Rasmussen's encephalitis showed reduced fibre density, cross-section, and edge weights in both ipsilesional and interhemispheric connections compared to controls.
• Longer disease duration correlated with decreased white matter integrity bilaterally but increased fibre density in the contralesional corticospinal tract.
• Network efficiency and intrahemispheric edge weights increased with disease duration in both hemispheres, suggesting compensatory mechanisms.

Conclusions:

• Rasmussen's encephalitis is a network disease affecting white matter throughout the brain, not confined to the lesioned hemisphere.
• The disease involves both degenerative white matter changes and adaptive network alterations.
• Early disease onset is associated with more widespread white matter integrity loss.