Demyelinating Lesions in Multiple Sclerosis: Plaques

Yes, demyelinating lesions in multiple sclerosis are indeed called plaques. 1

Characteristics of MS Plaques

MS plaques are focal areas of demyelination in the central nervous system, representing the hallmark pathological feature of the disease 1, 2
These lesions are typically visible on MRI as hyperintense areas on T2-weighted scans and can be found in both white and gray matter 1
MS plaques form around the microvasculature, with many showing a characteristic central vein (central vein sign) that helps distinguish them from other white matter abnormalities 1
Some chronic MS plaques develop a distinctive hypointense rim on susceptibility-based MRI, which may persist for years and reflects iron-laden microglia and/or macrophages at the lesion edge 1

White matter plaques are the most commonly recognized and are typically found in periventricular, juxtacortical, infratentorial, and spinal cord regions 1, 3
Cortical plaques involve the gray matter and have been classified into different types:
- Type I (leukocortical): affecting both gray matter and white matter 1
- Type II: small perivenous intracortical lesions not affecting white matter 1
- Type III: subpial demyelination extending inward from the brain surface (most frequent type) 1
- Type IV: lesions extending through the entire cortical width 1
Cortical plaques are more difficult to detect on conventional MRI but are better visualized with specialized sequences such as double inversion recovery (DIR), phase-sensitive inversion recovery (PSIR), or T1-weighted MPRAGE 1

Four distinct patterns of demyelination have been identified in MS plaques, suggesting heterogeneity in pathogenesis 4
Patterns I and II resemble T-cell-mediated or T-cell plus antibody-mediated autoimmune processes 4
Patterns III and IV suggest primary oligodendrocyte dystrophy, similar to virus or toxin-induced demyelination 4
Despite this heterogeneity between patients, multiple active lesions within the same patient typically show the same pattern 4

High-field MRI (3.0 Tesla) allows detection of significantly more lesions compared to lower field strengths, with improved recognition of cortical, infratentorial, and periventricular lesions 1, 5
Ultra-high-field MRI (7.0 Tesla) provides better definition of MS plaques with respect to their morphology and association with the vasculature 1, 5
The presence of a central small vein and rim of hypointensity on T2*-weighted imaging at high field strengths is a distinctive feature of MS plaques that helps differentiate them from other conditions 1, 5

MS plaques represent a common pathological endpoint of various immunological mechanisms of myelin destruction 6, 7
Beyond the visible focal plaques, MS also causes diffuse injury to normal-appearing white matter and gray matter, contributing to the overall disease burden 7, 2
Cortical plaques are particularly relevant for cognitive dysfunction in MS patients and are more prevalent in progressive forms of the disease 8
The distribution and characteristics of plaques help distinguish MS from other inflammatory demyelinating diseases 1, 3

MRI visualization of characteristic plaques is essential for MS diagnosis, demonstrating dissemination in space and time 1, 3
The term "plaque" is the standard pathological terminology for these lesions, reflecting their appearance as well-demarcated areas of demyelination 6, 2
Specific features of plaques, such as their perivenular location, shape, and distribution pattern, help differentiate MS from mimics 1