Axonal and myelin changes and their inter-relationship in the optic radiations in people with multiple sclerosis

Eva A Krijnen; Chanon Ngamsombat; Ilena C George; Fang F Yu; Qiuyun Fan; Qiyuan Tian; Susie Y Huang; Eric C Klawiter

doi:10.1177/20552173221147620

Axonal and myelin changes and their inter-relationship in the optic radiations in people with multiple sclerosis

Mult Scler J Exp Transl Clin. 2023 Feb 16;9(1):20552173221147620. doi: 10.1177/20552173221147620. eCollection 2023 Jan-Mar.

Authors

Eva A Krijnen^{1

2}, Chanon Ngamsombat^{3

4}, Ilena C George², Fang F Yu⁵, Qiuyun Fan^{6

7}, Qiyuan Tian³, Susie Y Huang³, Eric C Klawiter²

Affiliations

¹ MS Center Amsterdam, Anatomy and Neurosciences, Amsterdam Neuroscience, Amsterdam UMC location VUmc, Amsterdam, The Netherlands.
² Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
³ Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA.
⁴ Department of Radiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
⁵ Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
⁶ Department of Biomedical Engineering, College of Precision Instruments and Optoelectronics Engineering, Tianjin University, Tianjin, China.
⁷ Academy of Medical Engineering and Translational Medicine, Medical College, Tianjin University, Tianjin, China.

Abstract

Background: The imaging g-ratio, estimated from axonal volume fraction (AVF) and myelin volume fraction (MVF), is a novel biomarker of microstructural tissue integrity in multiple sclerosis (MS).

Objective: To assess axonal and myelin changes and their inter-relationship as measured by g-ratio in the optic radiations (OR) in people with MS (pwMS) with and without previous optic neuritis (ON) compared to healthy controls (HC).

Methods: Thirty pwMS and 17 HCs were scanned on a 3Tesla Connectom scanner. AVF and MVF, derived from a multi-shell diffusion protocol and macromolecular tissue volume, respectively, were measured in normal-appearing white matter (NAWM) and lesions within the OR and used to calculate imaging g-ratio.

Results: OR AVF and MVF were decreased in pwMS compared to HC, and in OR lesions compared to NAWM, whereas the g-ratio was not different. Compared to pwMS with previous ON, AVF and g-ratio tended to be higher in pwMS without prior ON. AVF and MVF, particularly in NAWM, were positively correlated with retinal thickness, which was more pronounced in pwMS with prior ON.

Conclusion: Axonal measures reflect microstructural tissue damage in the OR, particularly in the setting of remote ON, and correlate with established metrics of visual health in MS.

Keywords: Optic neuritis; diffusion magnetic resonance imaging; diffusion tractography; multiple sclerosis; optical coherence tomography; white matter.

Abstract

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