Visual Network Changes Due to Optic Neuritis
Published online Jan. 2, 2018
Backner et al. looked at anatomic and functional visual networks of patients with a first attack of optic neuritis (ON) and compared them with the visual networks of patients with symptoms of demyelination in other functional systems. They found that local demyelinating damage of the optic nerve did not affect distant wiring—and that functional modification was possible even in the presence of an intact anatomic network.
This prospective study involved 39 adults, 18 of whom had clinically isolated syndrome (CIS) ON. The remaining 21 had CIS unrelated to ON. Patients were enrolled 1 to 28 months following their initial clinical event and were required to have a suggestive clinical or paraclinical diagnosis of CIS or multiple sclerosis.
Anatomic connectivity was assessed by diffusion tensor imaging, and functional connectivity was evaluated by resting-state functional magnetic resonance imaging. Visual pathways were delineated (including optic tracts, optic radiations, and splenial fibers), and the resting-state visual networks were detected. Connectivity changes were quantified and compared.
Diffusion tensor imaging showed reduced diffusivity along the optic tracts of patients with ON, suggesting local extension of the optic nerve damage, but neither the optic radiations nor the splenial fibers showed loss of integrity. However, among patients with an intact postgeniculate anatomic network, functional connectivity within the visual network was higher in those with ON. The functional connectivity observed in areas related to cortical motion correlated inversely with conduction velocity measured by visual evoked potential.
It has been suggested that clinical outcomes for patients with multiple sclerosis are driven by remyelination as well as adaptive reorganization. The functional network changes observed in this study may play a role in the visual recovery process, but further research is needed to fully understand the mechanisms involved.
The original article can be found here.