Enhancement frequency decreases with increasing age in relapsing-remitting multiple sclerosis

Contrast enhancement found on MRI of patients with MS demonstrates areas of blood–brain barrier damage and inflammation. Contrast enhanced MRI shows evidence of disease activity five to 10 times more frequently than is indicated by clinically apparent relapse. However, the frequency of enhancement differs significantly among the different clinical MS phenotypes. It is much lower in patients with primary progressive MS (PPMS) than in those with secondary progressive MS (SPMS).1 Enhancement frequency is highest in relapsing-remitting MS (RRMS).2,3⇓ These differences in enhancement frequency among the clinical MS phenotypes has been interpreted as an indication that different mechanisms are responsible for disease evolution in the different phases or manifestations of the disease. However, recent experimental work has shown that clinical and pathologic manifestations of autoimmune demyelination are age dependent.4 This suggests that increasing age might also be responsible for the reduced frequency of enhancement seen in patients with PPMS or SPMS, who are typically older than those with RRMS. To address whether increasing age …