Highly Sensitive 3-Tesla Real Inversion Recovery MRI Detects Leptomeningeal Contrast Enhancement in Chronic Active Multiple Sclerosis.

BACKGROUND: Leptomeningeal contrast enhancement (LME) on T2-weighted Fluid-Attenuated Inversion Recovery (T2-FLAIR) MRI is a reported marker of leptomeningeal inflammation, which is known to be associated with progression of multiple sclerosis (MS). However, this MRI approach, as typically implemented on clinical 3-tesla (T) systems, detects only a few enhancing foci in ~25% of patients and has thus been criticized as poorly sensitive. PURPOSE: To compare an optimized 3D real-reconstruction inversion recovery (Real-IR) MRI sequence on a clinical 3 T scanner to T2-FLAIR for prevalence, characteristics, and clinical/radiological correlations of LME. MATERIALS AND METHODS: We obtained 3D T2-FLAIR and Real-IR scans before and after administration of standard-dose gadobutrol in 177 scans of 154 participants (98 women, 64%; mean ± SD age: 49 ± 12 years), including 124 with an MS-spectrum diagnosis, 21 with other neurological and/or inflammatory disorders, and 9 without neurological history. We calculated contrast-to-noise ratios (CNR) in 20 representative LME foci and determined association of LME with cortical lesions identified at 7 T (n = 19), paramagnetic rim lesions (PRL) at 3 T (n = 105), and clinical/demographic data. RESULTS: We observed focal LME in 73% of participants on Real-IR (70% in established MS, 33% in healthy volunteers, P < 0.0001), compared to 33% on T2-FLAIR (34% vs. 11%, P = 0.0002). Real-IR showed 3.7-fold more LME foci than T2-FLAIR ( P = 0.001), including all T2-FLAIR foci. LME CNR was 2.5-fold higher by Real-IR ( P < 0.0001). The major determinant of LME status was age. Although LME was not associated with cortical lesions, the number of PRL was associated with the number of LME foci on both T2-FLAIR ( P = 0.003) and Real-IR ( P = 0.0003) after adjusting for age, sex, and white matter lesion volume. CONCLUSIONS: Real-IR a promising tool to detect, characterize, and understand the significance of LME in MS. The association between PRL and LME highlights a possible role of the leptomeninges in sustaining chronic inflammation.

Slowly eroding lesions in multiple sclerosis.

BACKGROUND: At autopsy, 20%-40% of chronic multiple sclerosis (MS) lesions are labeled "slowly expanding" and feature myelin phagocytosis at the lesion edge. As pathological lesion classification relies on a single, terminal time point, the rate of lesion expansion cannot be directly measured. OBJECTIVE: To study long-term volume changes in individual MS lesions. METHODS: Volumes of individual lesions on proton density magnetic resonance imaging (MRI) acquired between 1992 and 2015 were measured in 22 individuals (one lesion per person). After correction for acquisition protocol, a mixed model evaluated lesion volume changes. RESULTS: The mean (standard deviation) lesion volume at baseline was 142 (82) mL, falling to 74 (51) mL after 16 (3) years. All lesions shrank over time. Change in lesion volume did not correlate with change in supratentorial brain volume ( p = 0.33). In simulations, the results could be explained by a process of slow radial expansion superimposed on substantially more rapid resorption of damaged tissue. CONCLUSION: We noted sustained radiological contraction of MS lesions, a surprising result given that fresh myelin breakdown products within chronic active lesions are observed relatively frequently at autopsy. Therefore, the primary pathological process in chronic lesions, even those described as "slowly expanding," is likely to be tissue loss.

Clinical 3-tesla FLAIR* MRI improves diagnostic accuracy in multiple sclerosis.

OBJECTIVE: To evaluate clinical fluid-attenuated inversion recovery (FLAIR)* 3T magnetic resonance imaging (MRI), which is sensitive to perivenular inflammatory demyelinating lesions, in diagnosing multiple sclerosis (MS). BACKGROUND: Central veins may be a distinguishing feature of MS lesions. FLAIR*, a combined contrast derived from clinical MRI scans, has not been studied as a clinical tool for diagnosing MS. METHODS: Two experienced MS neurologists evaluated 87 scan pairs (T2-FLAIR/FLAIR*), separately and side-by-side, from 68 MS cases, 8 healthy volunteers, and 11 individuals with other neurological diseases. Raters judged cases based on experience, published criteria, and a visual assessment of the "40% rule," whereby MS is favored if >40% of lesions demonstrate a central vein. Diagnostic accuracy was determined with area under the receiver operating characteristic curve (AUC), and inter-rater reliability was assessed with Cohen's kappa (κ). RESULTS: Diagnostic accuracy was high: rater 1, AUC 0.94 (95% confidence interval: 0.89, 0.97) for T2-FLAIR, 0.95 (0.92, 0.98) for FLAIR*; rater 2, 0.94 (0.90, 0.98) and 0.90 (0.85, 0.95). AUC improved when images were considered together: rater 1, 0.99 (0.98, 1.00); rater 2, 0.98 (0.96, 0.99). Inter-rater agreement was substantial for T2-FLAIR (κ = 0.68) and FLAIR* (κ = 0.74), despite low agreement on the 40% rule (κ = 0.47) ([Formula: see text] in all cases). CONCLUSIONS: Joint clinical evaluation of T2-FLAIR and FLAIR* images modestly improves diagnostic accuracy for MS and does not require counting lesions with central veins.

Sample-size calculations for short-term proof-of-concept studies of tissue protection and repair in multiple sclerosis lesions via conventional clinical imaging.

BACKGROUND: New multiple sclerosis (MS) lesion activity on magnetic resonance imaging (MRI) can test immunomodulatory therapies in proof-of-concept trials. Comparably powerful endpoints to assess tissue protection or repair are lacking. OBJECTIVE: The objective of this paper is to report sample-size calculations for assessment of new lesion recovery. METHODS: In two sets of six active MS cases, new lesions were observed by monthly MRI for approximately 12 months. Averages and quartiles of normalized (proton density/T1/T2 weighted) and quantitative (T1/T2 and mean diffusivity maps for dataset 1, T2 and magnetization transfer ratio maps for dataset 2) measures were used to compare the lesion area before lesion appearance to afterward. A linear mixed-effects model incorporating lesion- and participant-specific random effects estimated average levels and variance components for sample-size calculations. RESULTS: In both datasets, greatest statistical sensitivity was observed for the 25th percentile of normalized proton density-weighted signal. At 3T, using new lesions ⩾15 mm(3), as few as nine participants/arm may be required for a six-month placebo-controlled add-on trial postulating a therapeutic effect size of 20% and statistical power of 90%. CONCLUSION: Lesion recovery is a powerful outcome measure for proof-of-concept clinical trials of tissue protection and repair in MS. The trial design requires active cases and is therefore best implemented near disease onset.