[Multiple sclerosis: imaging, diagnostic criteria and differential diagnosis]

Area of Science:

• Neurology
• Neuroimmunology
• Radiology

Context:

• Multiple sclerosis (MS) is the primary demyelinating inflammatory disease affecting the central nervous system (CNS).
• MS is characterized by multifocal inflammatory lesions (plaques) primarily in the white matter.
• Traditional Magnetic Resonance Imaging (MRI) visualizes these plaques but may underestimate disease extent.

Purpose:

• To highlight that visible MS plaques represent only a fraction of the disease's impact.
• To emphasize the early occurrence of neuroaxonal damage and diffuse brain involvement in MS.
• To showcase advanced MRI techniques and biomarkers reflecting sub-clinical changes.

Summary:

• MS involves widespread neuroaxonal damage and diffuse brain parenchyma infiltration, extending beyond macroscopic lesions.
• Early MS manifestations include T1-weighted hypointense lesions, early-onset atrophy, reduced N-acetylaspartate (NAA), decreased magnetization transfer ratio (MTR), and altered diffusion-weighted imaging (DWI) parameters.
• These imaging biomarkers indicate sub-clinical pathology in normal-appearing white matter.

Impact:

• MRI is crucial for diagnosing MS by demonstrating lesion dissemination in space and time.
• Advanced imaging metrics improve diagnostic specificity and differentiate MS from other white matter disorders.
• Understanding the full extent of MS pathology aids in developing more effective therapeutic strategies.