[Pathogenesis of cognitive impairment in multiple sclerosis]

Around a half of multiple sclerosis (MS) patients suffer from cognitive impairment such as attention deficit. A similar impairment is already observable in one third of patients with clinical isolated syndrome, suggesting that the symptom cannot be solely explained by the accumulation of demyelinated lesions. Recently, several studies indicated that demyelination and atrophy in specific regions of the brain are related to the cognitive impairment, although those patients with brain and cognitive reserves are resistant to the development of such symptom. Aging, male sex and smoking increases whereas certain disease-modifying therapy decreases the risk of cognitive impairment in MS. Together, the development of cognitive impairment in MS appears to be determined by the balance between specific aggravating and protective factors.