Leptomeningeal enhancement in multiple sclerosis demonstrates posterior predilection and T₁alterations in the adjacent cortex

Background: Leptomeningeal enhancement (LME) is a putative magnetic resonance imaging (MRI) marker of meningeal inflammation in multiple sclerosis (MS). 3D inversion-prepared fast-spin-echo sequence with real-reconstruction inversion recovery (Real-IR) MRI at 3 tesla (T) is highly sensitive to LME. Objectives: To assess LME prevalence across brain regions and characterize the relationship between LME and subtle cortical pathology. Methods: LME distribution patterns across brain regions were recorded for 90 adults (Age: 51 ± 11; women: 57; MS: 78) using 3T Real-IR. A subset of 15 participants had corresponding T₁-maps at 7T. T₁ relaxation times were calculated in the normal-appearing cortex subjacent to the LME, in comparison to the adjacent and homologue cortex. Results: 243 LME foci were found across 65 participants (73%). One hundred and sixty-one (66.3%) LME foci were posterior to the central sulcus. Three of 15 7T participants had a cortical lesion nearby LME (3/49 foci). Mean T₁ times within cortex beneath LME (1734 ± 135 ms) were elevated compared to homologue (1668 ± 167 ms, p = .0052) and adjacent cortex (1651 ± 133 ms, p < .0001). Conclusions: Regional variations in LME distribution may point to topographical differences in the blood-meningeal barrier. Alterations in T₁ relaxation time observed in the cortex adjacent to LME may signify subtle tissue changes in the absence of cortical lesions.