Abstract
Objectives Structural connectivity and graph theory analysis may elucidate substrates for cognitive impairment in MS, providing additional biomarkers for disease progression in addition to conventional MRI analysis. We investigated the association between global network metrics and cognitive impairment cross-sectionally and longitudinally over 24 months.
Methods 48 patients with relapsing-remitting MS were recruited for an observational study over 24 months. Processing speed, learning/memory, executive function and language were assessed with the Minimal Assessment of Cognitive Function in MS (MACFIMS) battery. Patients were divided into cognitively-impaired (Z score <-1SD for ≥ 2 tests) versus cognitively-preserved at baseline. Structural connectomes were reconstructed using diffusion-weighted imaging and probabilistic tractography.
Network metrics and cognitive scores were analysed at baseline, and network metric changes were correlated with cognitive changes over 24 months.
Results Mean age was 30 years, 63% female, median disease duration 1.88 years, median EDSS 2.0. At baseline, network metrics were not correlated with any cognitive outcomes after adjusting for age, gender and T2 lesion volume. Between cognitively impaired (n=25) and preserved patients (n=23), there was no difference in lesion volume, normalised gray matter volume, or network metrics. Baseline EDSS was not significantly correlated with any graph measures. Over two years, change in executive function was negatively correlated with change in mean local efficiency, clustering co- efficient and assortativity (p<0.05).
Conclusion Global network metrics were not correlated with cognitive outcomes or EDSS scores, and did not differentiate between cognitively impaired vs preserved patients. Longitudinal changes in global network metrics are associated with cognitive decline.
