Comparison of MS clinical phenotypes using conventional and magnetization transfer MRI

Objective: To identify differences in pathology between the principal clini cal phenotypes of MS using conventional and magnetization transfer (MT) MRI . Methods: T1-weighted and T2-weighted images as well as MT scans were obta ined from 20 controls, 21 patients presenting with clinically isolated synd romes suggestive of MS, and 93 MS patients with relapsing-remitting seconda ry progressive, benign, or primary progressive course. Metrics considered: hypointense T1 and T2 lesion volumes, average lesion MT ratio, average brai n MT ratio, peak height and position from MT histograms. Results: MS patien ts had lower MT metrics than controls. Patients with clinically isolated sy ndromes had MT measures similar to controls, whereas primary progressive MS patients had lower histogram peak height with normal peak position. Relaps ing-remitting MS patients had lower MT measures, higher T2 lesion load and ratio of hypointense T1 to T2 lesion volumes than patients with clinically isolated syndromes, and lower MT ratio and peak height than benign MS patie nts. Benign MS patients were similar to controls and patients with clinical ly isolated syndromes. Secondary progressive MS patients had the lowest MT measures and highest lesion loads. Conclusions: Pathology in patients with clinically isolated syndromes is confined to modest tissue damage in the le sions seen on T2-weighted scans. Severe damage is important for the later d evelopment of disability. However, microscopic damage in normal-appearing w hite matter may be a major contributor to disability in primary progressive MS.