Slowly expanding/evolving lesions as a magnetic resonance imaging marker of chronic active multiple sclerosis lesions

Area of Science:

• Neuroimaging
• Radiology
• Neurology

Background:

• Smoldering inflammation drives chronic lesion activity in progressive multiple sclerosis (MS).
• Understanding lesion evolution is crucial for managing MS progression.
• Current methods may not fully capture chronic, low-grade inflammatory processes.

Purpose of the Study:

• Develop an automated method to detect slowly expanding/evolving lesions (SELs) using conventional brain MRI.
• Characterize SELs in patients with relapsing MS (RMS) and primary progressive MS (PPMS).
• Investigate the association of SELs with disease subtypes and lesion characteristics.

Main Methods:

• Defined SELs by local expansion using Jacobian determinant analysis of serial MRI scans.
• Employed a heuristic scoring system for SEL candidates based on concentricity and change constancy.
• Analyzed SELs in large cohorts of 1334 RMS and 555 PPMS patients.

Main Results:

• PPMS patients exhibited significantly higher numbers and T2 volumes of SELs compared to RMS patients.
• SELs were consistently devoid of gadolinium enhancement, indicating no acute inflammation.
• SELs showed lower baseline T1 intensity and a greater decrease over time, suggesting chronic tissue loss.

Conclusions:

• SELs likely represent chronic tissue loss without active inflammation in MS.
• SELs may serve as a conventional MRI biomarker for smoldering inflammation in MS.
• This detection method aids in understanding MS pathology and progression.