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Magnetic resonance imaging lesion enlargement in multiple sclerosis. Disease-related activity, chance occurrence, or
D E Goodkin1, J S Ross, S V Medendorp
1Mellen Center for Multiple Sclerosis Treatment and Research, Cleveland Clinic Foundation, OH 44195-5244.
Abstract:
Magnetic resonance imaging (MRI) may demonstrate disease activity in a number of ways in patients with multiple sclerosis. Newly appearing MRI lesions, gadolinium-enhancing lesions, and enlargement of preexisting lesions are frequently taken as evidence of disease activity. Furthermore, serial MRI studies have been stated to be more sensitive than repeated neurologic examinations in detecting disease activity. We assessed the validity of using lesion enlargement as a measure of disease activity by repeatedly measuring the area of all MRI lesions in four patients with multiple sclerosis. The size-frequency distribution in all patients was similar, with 80% of the lesions measuring less than 0.67 cm2. The median coefficient of variation for three successive lesion measurements was inversely related to lesion area, ranging from 22.6% for the more common smaller lesions (less than 0.67 cm2) to 12.1% for larger lesions. Based on these coefficients of variation, a change in a particular lesion exceeding 45.2% for a baseline lesion smaller than 0.67 cm2 and 24.2% for a baseline lesion greater than or equal to 0.67 cm2 should be required to exclude a change due to measurement variability. It remains necessary to determine the number of lesions that must change when multiple lesions are present in the baseline MRI to reliably exclude chance occurrence when establishing MRI-evident disease activity. Guidelines for determining these criteria are presented, as are the limitations inherent in the statistical model employed to make these determinations.
Insights
Assessing multiple sclerosis disease activity with magnetic resonance imaging (MRI) requires careful consideration of lesion size changes. Significant lesion enlargement, beyond measurement variability, is crucial for accurately detecting disease progression via MRI scans.
Area of Science:
- Neuroimaging
- Neurology
- Radiology
Background:
- Magnetic resonance imaging (MRI) is pivotal in monitoring multiple sclerosis (MS) disease activity.
- Common indicators of MS activity include new or enlarging lesions and gadolinium enhancement.
- Serial MRI studies are considered more sensitive than neurological exams for detecting disease activity.
Purpose of the Study:
- To evaluate the reliability of lesion enlargement as a metric for multiple sclerosis disease activity.
- To establish criteria for determining significant lesion changes on MRI, accounting for measurement variability.
Main Methods:
- Repeatedly measured the area of all MRI lesions in four patients with multiple sclerosis.
- Analyzed lesion size-frequency distribution and calculated coefficients of variation for lesion measurements.
- Determined percentage changes in lesion area required to exclude measurement variability.
Main Results:
- Eighty percent of lesions measured less than 0.67 cm², indicating a prevalence of smaller lesions.
- Median coefficients of variation were 22.6% for smaller lesions (<0.67 cm²) and 12.1% for larger lesions (≥0.67 cm²).
- A change >45.2% for small lesions and >24.2% for large lesions is needed to confirm true enlargement beyond measurement error.
Conclusions:
- Significant lesion enlargement on serial MRI is a valid indicator of multiple sclerosis disease activity.
- Specific percentage changes in lesion size are proposed to differentiate true progression from measurement variability.
- Further research is needed to define criteria for multiple lesion changes to reliably confirm MRI-evident disease activity.