Serial Gadolinium-enhanced MRI in untreated patients with acute optic neuritis: implications for natural history

Serial brain MRIs with and without Gadolinium (Gd)-DTPA were performed in acute optic neuritis (ON).

Fifty-nine untreated patients (44 female) aged 20-57 years with ON underwent MRI median 16 d from onset of symptoms of ON and at 1 and 12 months follow-up.

At onset of monosymptomatic ON (AMON), 13 of 40 (33%) patients had lesions on MRI without Gd-DTPA compared with 15 of 19 (79%) patients with ON as part of clinically definite multiple sclerosis (CDMS). An initially abnormal MRI never normalized, whereas 3 patients with AMON with initially normal MRI had lesions at follow-up. In AMON enhancing lesions were seen in 5% of patients at onset, in 12% after 1 month, and in 11% after 12 months. The corresponding figures in CDMS were 21%, 38%, and 33%. All enhancing lesions were also seen on MRI without Gd-DTPA. The number of lesions on MRI without Gd-DTPA increased significantly with time in the 8 patients with AMON with enhancing lesions at one or more MRIs. New enhancing lesions appeared in 11 patients (6 AMON), of whom 3 (2 AMON) had an exacerbation. In contrast, 12 (5 AMON) patients had an exacerbation, being accompanied by new enhancing lesions in only 3 (2 AMON) patients.

Gd-DTPA did not increase the sensitivity of MRI, which was significantly higher in CDMS than in AMON, but improved the understanding of the natural history of AMON and CDMS. The dynamics of enhancing lesions did not correlate well with exacerbations. Serial MRI and clinical assessment are supplementary in monitoring disease activity.