To examine whether changes associated with optic neuritis (ON) in the structural and functional networks, can still be discerned in progressive multiple sclerosis (MS) patients, even years after the acute insult.

The brain's ability to adapt in response to damage is debated in MS literature. In a previous work, we have shown that following acute damage caused to the visual system by an episode of ON, the functional visual network experiences changes that are associated with the specific neurologic deficit, all within the limits of the underlying disease pathophysiology.

Forty-eight progressive MS patients, with and without prior ON (n_MS-ON = 21, n_MS-nON = 27), underwent structural and functional magnetic resonance imaging (MRI), including diffusion tensor imaging and resting state fMRI. Anatomical and functional visual networks were defined using 50 visual regions-of-interest. Data were analyzed using graph theory-based methods and weighted network metrics were extracted, including density, strength, global and local efficiency, and modularity.

The anatomical networks of the MS-ON group appear to be more damaged than those of the MS-nON group, while the functional networks appear to function to the same degree. Anatomical connectivity seems influenced by the long- standing distal damage to the optic nerve, suggesting trans-synaptic effects. However, despite our previous study having shown possibly-adaptive functional changes in the visual network following acute ON, this ability appears to be nullified in progressive patients.