Characterizing contrast-enhancing and re-enhancing lesions in multiple sclerosis.

Area of Science:

• Radiology
• Neuroimaging
• Neurology

Background:

• Contrast-enhancing lesions (CELs) in T1-weighted postcontrast MRI signify blood-brain barrier breakdown in multiple sclerosis (MS).
• The significance of re-enhancement in chronic CELs as an indicator of distinct pathology is not well understood.

Purpose of the Study:

• To determine the incidence of re-enhancing lesions (re-CELs) originating from chronic MS plaques.
• To compare new CELs (n-CELs) and re-CELs regarding size, magnetization transfer ratio (MTR), and likelihood of forming acute black holes (aBHs).
• To explore associations between re-CELs and indicators of advanced MS disease.

Main Methods:

• Retrospective analysis of 264 monthly MRI scans from 88 MS patients over three months.
• CELs were classified as new (n-CELs) if absent on baseline T2W MRI, or re-enhancing (re-CELs) if present on baseline T2W MRI.

Main Results:

• A total of 311 n-CELs (82.7%) and 65 re-CELs (17.3%) were identified.
• Patients with both lesion types showed a higher overall CEL count.
• Re-CELs were significantly larger and exhibited lower MTR compared to n-CELs, suggesting distinct inflammatory characteristics.

Conclusions:

• Approximately 20% of CELs in MS represent re-enhancement of chronic lesions.
• Re-CELs are associated with larger inflammatory areas but not necessarily with larger edema volumes.
• These findings suggest re-CELs may represent a different pathological process than new CELs in MS.