Visual resting-state network in relapsing-remitting MS with and without previous optic neuritis

OBJECTIVE: To investigate functional connectivity of the visual resting-state network (V-RSN) in normal-sighted relapsing-remitting multiple sclerosis (RRMS) patients with and without previous optic neuritis (ON). METHODS: Thirty normal-sighted RRMS patients, 16 without (nON-MS) and 14 with (ON-MS) previous ON, and 15 age- and sex-matched healthy controls (HCs) underwent a neuro-ophthalmologic evaluation, including automated perimetry and retinal nerve fiber layer (RNFL) measurement, as well as an MRI protocol, including structural and resting-state fMRI (RS-fMRI) sequences. Functional connectivity of the V-RSN was evaluated by independent component analysis (ICA). Regional gray matter atrophy was assessed by voxel-based morphometry (VBM). A correlation analysis was performed between RS-fMRI results and clinical, neuro-ophthalmologic, and structural MRI variables. RESULTS: Compared to HCs, patients with RRMS showed a reduced functional connectivity in the peristriate visual cortex, bilaterally. Compared to nON-MS, ON-MS patients revealed a region of stronger functional connectivity in the extrastriate cortex, at the level of right lateral middle occipital gyrus, as well as a region of reduced functional connectivity at the level of right inferior peristriate cortex. These latter changes correlated with the number of previous ON. All detected V-RSN changes did not colocalize with regional gray matter atrophy. CONCLUSIONS: Normal-sighted RRMS patients show a significant functional disconnection in the V-RSN. RRMS patients recovered from a previous ON show a complex reorganization of the V-RSN, including an increased functional connectivity at the level of extrastriate visual areas.