Patterns of enhancing lesion evolution in multiple sclerosis are uniform within patients

Background: Histopathologic studies suggest that lesion development differs between patients with multiple sclerosis ( MS), but that all lesions appear similar within patients. It is unclear whether the same applies to the evolution of lesions on T1-weighted MRI. Objective: To evaluate lesion evolution on MRI, comparing variance within and between patients, as well as the relationship between MRI lesion development and clinical characteristics. Methods: In 48 patients, signal intensity at baseline and at follow-up on T1-weighted MRI of 789 newly enhancing lesions was studied in relationship with clinical data. Patients were included on the basis of showing at least five enhancing lesions that could be followed on monthly scans for 6 months. Variance component analysis and multilevel analysis were used to compare within-patient and between-patient variability. Results: Although various types of lesion evolution could be observed within a single patient, between-patient variance was considerably larger than within-patient variance for MRI parameters used to describe lesion evolution, indicating that lesion evolution is a patient-specific phenomenon. Evolution of lesions in patients with secondary progressive disease more frequently followed a hypointense-hypointense pattern than in patients with relapsing-remitting disease ( odds ratio 4.2). Patients with a benign disease course had more persistent isointense lesions at follow-up, whereas patients with aggressive disease had more hypointense lesions. Conclusion: Lesion evolution on MRI appears to be a patient-specific phenomenon, although the outcome seems to vary according to the phase and severity of the disease.