Abstract Details

Title Imaging G-ratio Changes In The Optic Radiations In People With Multiple Sclerosis

Topic Multiple Sclerosis

Presentation(s) MS and CNS Inflammatory Disease Posters (7:00 AM-5:00 PM)

Poster/Presentation
Number 160

Objective

To assess changes in the imaging g-ratio in the optic radiations (OR) in people with multiple sclerosis (pwMS) with and without previous optic neuritis (ON) compared to healthy controls (HC).

Background The imaging g-ratio, comprised of the ratio of axonal diameter to the diameter of the axon plus myelin, and its components, the axonal volume fraction (AVF) and myelin volume fraction (MVF), reflect integrity of tissue microstructure in MS.

Design/Methods We conducted a cross-sectional evaluation of 30 pwMS and 17 HCs scanned on a 3 Tesla MRI equipped with ultra-high gradients. AVF, derived from a multi-shell diffusion protocol and analyzed with a 3-compartment model using a spherical mean approach, and MVF, derived from macromolecular tissue volume, were used to calculate the g-ratio. These metrics were measured in normal-appearing white matter (NAWM) and T2-hyperintense lesions (T2H) within the OR. Retinal nerve fiber layer (RNFL) and ganglion cell analysis (GCA) were measured by optical coherence tomography.

Results

AVF and MVF were decreased in pwMS compared to HC in OR (0.225 vs. 0.260,p=0.001; 0.266 vs. 0.290,p=0.039). In pwMS, AVF and MVF were lower in OR T2H compared to OR NAWM (0.158 vs. 0.227,p<0.001; 0.200 vs. 0.268,p<0.001). Compared to pwMS with a history of ON, AVF and g-ratio were higher in pwMS without prior ON (0.251 vs. 0.208,p=0.011; 0.676 vs. 0.647,p=0.038). AVF in NAWM, T2H and whole OR show moderate positive correlations with RNFL (r=0.46-0.66,p=0.001-0.044) and GCA (r=0.51-0.63,p=0.001-0.021). PwMS without prior ON had a moderate positive correlation between RNFL and OR g-ratio, and between RNFL and AVF (r=0.63,p=0.028 and r=0.59,p=0.043, respectively). In pwMS and prior ON, GCA and RNFL showed a strong positive correlation with OR AVF (r=0.76,p=0.007; r=0.81,p=0.003).

Conclusions AVF, MVF and imaging g-ratio may reflect microstructural tissue damage in the OR, particularly in the setting of remote ON, and correlate with established metrics of visual health.

Authors/Disclosures
Eva Angela Krijnen (Mass General Brigham) PRESENTER	Ms. Krijnen has nothing to disclose.
	No disclosure on file
Ilena George, MD	The institution of Dr. George has received research support from Biogen.
	No disclosure on file
	No disclosure on file
Susie Y. Huang, MD, PhD (Massachusetts General Hospital, Harvard Medical School)	Dr. Huang has received personal compensation in the range of $0-$499 for serving as a Consultant for Siemens Healthineers. The institution of Dr. Huang has received research support from Siemens Healthineers. The institution of Dr. Huang has received research support from Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School.
Eric Klawiter, MD, FAAN (Massachusetts General Hospital)	Dr. Klawiter has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Galen/Atlantica. Dr. Klawiter has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Genentech. Dr. Klawiter has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Banner Life Sciences. Dr. Klawiter has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Greenwich Biosciences. Dr. Klawiter has received personal compensation in the range of $10,000-$49,999 for serving on a Scientific Advisory or Data Safety Monitoring board for OM1. Dr. Klawiter has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for TG Therapeutics. The institution of Dr. Klawiter has received research support from Biogen. The institution of Dr. Klawiter has received research support from Abbvie. The institution of Dr. Klawiter has received research support from Genentech.

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