MRI Characteristics Reflect Specific MS Immunopatterns

Disease Spotlight | <b>Disease Spotlight: Multiple Sclerosis</b>

Instead of a smooth-contoured, thin, and regular ring or arc typically seen, pattern 3 patients had atypical rings such as irregularly thick rings and arcs.

Using a retrospective cohort study, investigators concluded that analyzing MRI lesion characteristics correlate with multiple sclerosis (MS) immunological patterns of demyelination. More specifically, ring enhancement and hypointense T2-weighted (T2w) rims were significantly associated with patterns 1 and 2, but not pattern 3.

Senior author Claudia F. Lucchinetti, MD, staff neurologist, Mayo Clinic, and colleagues evaluated the MRI lesion characteristics of 789 conventional prebiopsy and follow-up MRIs in in relation to their histopathologically classified immunopathological patterns (n = 161) and lesion edge features (n = 112). In total, 24% of cases had immunopathological pattern 1, 56% pattern 2, and 20% pattern 3.

A strong association of a ringlike enhancement was found in the majority of pattern 1 (59%) and pattern 2 patients (65%), and only in a minority of pattern 3 patients (23%; n = 5). Additionally, ring enhancing lesions of pattern 3 patients did not reveal a smooth-contoured, thin and regular ring or arc that was typical for pattern 1 and 2 patients. Instead, when present at all, they were atypical rings such as irregularly thick rings or arcs.

A strong association was found between the 43% of patients who showed a hypointense T2w rim and their immunopatterns (P = .003). Around 44% of pattern 1 patients and 53% of pattern 2 patients showed a hypointense T2w rim on the index lesion, in contrast to 13% of pattern 3 patients.

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In total, 39% of patients had an index lesion with both ringlike enhancement and a T2w rim, which were found to be strongly linked to each other (odds ratio [OR], 14.0 [95% CI, 5.2-4.7]; P <.001). Notably, 69% of those with a ring enhancing index lesion on prebiopsy MRI also had T2w rims in the index lesion. In contrast, 88% of individuals with no ring enhancing lesion had no rim. This relationship held in each of the immunopatterns, with the OR being approximately 4 (95% CI, 1-33) in pattern 1 cases, 11 (95% CI, 3-45) in pattern 2 cases, and 19 (95% CI, 1-1167) in pattern 3 cases.

Investigators found a strong association (OR, 4.8 [95% CI, 2.1-23.3]; P <.001) when analyzing the concordance of the ring enhancement of the index lesion on prebiopsy MRIs with the enhancement of any other nonbiopsied lesions. When the index lesion was ring enhancing, 61% of patients showed other ring enhancing lesions. Vice versa, among those whose index lesion showed no ringlike enhancement, 78% of patients had no other lesions that showed a ringlike enhancement pattern.

Among patients with multifocal lesions, 70% had gadolinium-enhancing lesions in addition to the biopsied lesion on prebiopsy MRI, with multiple enhancing lesions common (16% having 1, 20% having 2-5, 13% having 6-10, and 21% having more than 10). Pattern 3 patients were more likely to show a heterogenous enhancement pattern on the index lesion or other, non-biopsied lesions (72% vs 47% for pattern 1 and 52% for pattern 2; overall, P = .013) despite fewer patients within this group showing ringlike enhancing lesions.

Edema was located in the majority (76%) of prebiopsy MRIs; however, investigators concluded that the differences between immunopatterns were not statistically significant enough (P = .06) to show actual difference. Additionally, no statistically significant differences were observed for a mass effect (P = 0.43), which occurred in 55% of pattern 1 patients and 41% in both pattern 2 and 3 patients, respectively.

Lucchinetti has a background in investigating the immunopathology and pathogenesis of MS, neuromyelitis optica, and other central nervous system (CNS) inflammatory demyelinating disorders. She recently published research that showed that that clinical-radiographic-cognitive outcomes in patients with pathologically confirmed central nervous system (CNS) demyelinating disease are comparable to those with typical MS.

Metz I, Gavrilova RH, Weigand SD, et al. Magnetic resonance imaging correlates of multiple sclerosis immunopathological patterns. Ann Neurol. Published online July 7, 2021. doi: 10.1002/ana.26163