Prognostic value of MR and magnetization transfer imaging findings in patients with clinically isolated syndromes suggestive of multiple sclerosis at presentation.

BACKGROUND AND PURPOSE The extent of abnormalities on T2-weighted MR images of the brain of patients with clinically isolated syndromes (CIS) suggestive of multiple sclerosis (MS) at presentation is associated with an increased risk of developing clinically definite MS (CDMS). We evaluated whether subtle changes outside T2-visible lesions are present in the brain of these patients and whether their extent increases the risk of subsequent development of CDMS. METHODS Dual-echo, T1-weighted, and magnetization transfer (MT) images of the brain were obtained from 24 patients with CIS at presentation. These patients were followed up for a mean period of 33 months (range, 25-42 months). Twenty age- and sex-matched healthy volunteers served as control subjects. To create MT histograms of the normal-appearing brain tissue (NABT), macroscopic lesions were segmented from dual-echo images, were superimposed automatically, and were nulled out from the coregistered and scalp-stripped MT ratio (MTR) maps. The following MTR histogram-derived measures were considered: average MTR, MTR(25), MTR(50), MTR(75), peak height, and peak position. T2 and T1 lesion loads, average lesion MTR, and brain volume were also measured. RESULTS Patients with CIS had lower average NABT-MTR (P < .0001) and peak position (P = .002) than did control volunteers, but patient brain size was similar to that of volunteers. At follow-up, 10 (41%) patients developed CDMS. Patients who developed CDMS during the follow-up period had higher T2 lesion volume (P = .003) and lower average NABT-MTR (P = .005) and peak position (P = .006) than did those who did not develop CDMS. T2 lesion volume (odd ratio, 3.54; P = .0005) and average NABT-MTR (odd ratio, 0.81; P = .01) were independent predictors of the subsequent development of CDMS. CONCLUSION Subtle changes occur outside lesions visible on conventional MR images among patients with CIS suggestive of MS at presentation. The greater the extent of such abnormalities is, the higher is the risk of subsequent development of CDMS.