Neurophysiological correlates of cognitive disturbances in multiple sclerosis.

Cognitive impairment is common in multiple sclerosis, mostly attributed to involvement of cortico-cortical and cortico-subcortical connections. The latter may be explored using the analysis of bioelectrical activity such as power and coherence of the electroencephalogram at rest and its reactivity to stimulus processing and cognitive activities, such as event-related desynchronization and event-related potentials. Although these methods are very useful for assessing information processing during cognitive tasks and other activities, their value in detecting cognitive impairment concerning sensitivity and specificity needs to be validated and they have been mostly used for understanding the physiopathology of cognitive impairment in different forms and stages of the diseases. Nevertheless, newer applications such as longitudinal monitoring and effects of treatment, although explored only in pilot studies, seem quite promising allowing objective measures potentially useful as secondary endpoints in clinical trials aimed at preserving or improving cognition in MS patients.