Reduced Myelin Signal in Normal-appearing White Matter in Neuromyelitis Optica Measured by 7T Magnetic Resonance Imaging

I-Jun Chou,Gordon Mazibrada,Olivier E Mougin,Esmaeil Nikfekr,Christopher R Tench,Basil Sharrack,Bruno Gran,William P Whitehouse,Radu Tanasescu,Penny A Gowland,Cris S Constantinescu

doi:10.1038/s41598-019-50928-0

Abstract

Whether the integrity of normal-appearing white matter (NAWM) is preserved in neuromyelitis optica spectrum disorders (NMOSD) is open to debate. To examine whether the tissue integrity of NAWM in NMOSD is compromised compared to that in healthy controls and patients with multiple sclerosis (MS), we prospectively enrolled 14 patients with NMOSD, 12 patients with MS, and 10 controls for clinical functional assessments and quantitative imaging, including T1 relaxation time (T1) and magnetization transfer ratio (MTR) at 7 Tesla. Cognitive performance on the Paced Auditory Serial Addition Test with a 3-second interstimulus interval (PASAT-3) was significantly lower in the NMOSD compared to the MS group (mean number of correct answers, 34.1 vs. 47.6; p = 0.006), but there were no differences in disease duration or disability. Histograms of T1 and MTR maps of NAWM demonstrated a decreased peak height in patients with NMOSD compared to the healthy controls, but not compared to patients with MS. Using 7T quantitative magnetic resonance imaging (MRI), this study showed that the NAWM in patients with NMOSD is abnormal, with reduced myelin signal; this was not previously observed using MRI at a lower field strength.

Highlights

P 0.416 0.769 n/a n/a n/a being assessed histopathologically[12,13,14,15]
The date of the magnetic resonance imaging (MRI) scan was separated from a clinical attack by at least 30 days
One of the patients with neuromyelitis optica spectrum disorders (NMOSD) was treated with corticosteroids alone, and the others received long-term immunosuppressants: five had azathioprine, five had rituximab, and three had mycophenolate mofetil; of these patients, three combined their treatment with low-dose corticosteroids

Summary

Introduction

At 7T, both quantitative T1 mapping and the MTR can detect changes within NAWM in clinically isolated syndromes and relapsing-remitting MS (RRMS) relative to healthy controls[16] via imaging with submillimetre resolution. Quantitative imaging at 7T is capable of revealing the damaged substrate within WM lesions and NWAM in NMOSD. Based on aforementioned MRI and histological findings, we hypothesized that (1) the extent of structural change of WM lesions in NMOSD is more severe than in MS, but that (2) the integrity of NAWM in NMOSD is less compromised than in MS. We prospectively enrolled patients with NMOSD, patients with MS, and healthy participants and acquired brain MRI images at 7T, for comparison of the measured T1 relaxation time and MTR maps among the groups

Methods

Results

Discussion

Conclusion