A functional reorganization characterized by hypo-synchronicity of functionally-related/hyper-synchronicity of functionally-segregated large scale networks and an abnormal pattern of neural activity underlie cognitive dysfunction in primary-progressive multiple sclerosis (PP-MS), a recent study found. Furthermore, cortical lesions (CLs) possibly play a role in variability and functional connectivity abnormalities. Researchers analyzed functional connectivity and variability (measured as the standard deviation of BOLD signal amplitude) in resting state networks (RSNs) associated with cognitive deficits in different frequency bands in 25 PP-MS patients (mean age 50.9 ± 10.5 years) and 20 healthy subjects (mean age 51.0 ± 9.8 years). They found:

• This study confirmed the presence of a widespread cognitive deterioration in PP-MS patients, with main involvement of visuo-spatial and executive domains.
• Cognitively impaired patients showed increased variability, reduced synchronicity between networks involved in the control of cognitive macro-domains, and hyper-synchronicity limited to the connections between networks functionally more segregated.
• CL volume was higher in patients with cognitive impairment and was correlated with functional connectivity and variability.