Abstract Details

Title Glutamate-weighted CEST (GluCEST) MRI contrast at the site of transcranial magnetic stimulation is related to changes in motor evoked potentials

Topic Aging, Dementia, and Behavioral Neurology

Presentation(s) P3 - Poster Session 3 (5:30 PM-6:30 PM)

Poster/Presentation
Number 9-019

Objective

To test whether local glutamate-weighted chemical exchange saturation transfer (GluCEST) imaging contrast is related to motor evoked potentials after transcranial magnetic stimulation (TMS) at area M1.

Background Concerns about response variability following TMS and specifically continuous theta burst stimulation (cTBS) call for objective in vivo biomarkers to support personalized interventions. Further, while cTBS canonically reduces motor evoked potentials (MEPs) for 60 minutes or longer post-stimulation, the consistency of this effect and its mechanism has been debated. CEST imaging at high field strengths facilitates measurements of Glu changes at the site of TMS. Here, we tested whether the GluCEST changes at the site of cTBS is a viable biomarker for TMS.

Design/Methods cTBS at 80% active motor threshold was administered to a M1 site that caused MEPs in the right first dorsal interosseus in 5 subjects between repeated sessions of GluCEST with Siemens 7T TERRA whole body magnetic resonance imaging (MRI) scanner. GluCEST contrast at the site of stimulation was measured before and after stimulation. MEP changes immediately after and 30 minutes after cTBS were recorded.

Results

Baseline GluCEST contrast at M1 was strongly negatively correlated (R = -0.91) with MEP changes. In addition, changes in GluCEST contrast were strongly positively correlated (R = 0.84) with MEP changes following cTBS. Subjects with the highest GluCEST contrast at baseline are more likely to have strong inhibitory responses to cTBS.

Conclusions GluCEST MRI can serve as a potential biomarker for responses to cTBS at baseline. In addition, GluCEST contrast changes may partially mediate cTBS effects to descending motor pathways from M1.

Authors/Disclosures
John D. Medaglia, PhD (Drexel University) PRESENTER	The institution of Dr. Medaglia has received research support from National Institutes of Health.
	No disclosure on file
	No disclosure on file
	No disclosure on file
	No disclosure on file
	No disclosure on file
Eric McConathey	No disclosure on file
	No disclosure on file
Roy H. Hamilton, MD, MS, FANA, FAAN	Dr. Hamilton has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Highland Instruments. Dr. Hamilton has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for Cognito Therapeutics. Dr. Hamilton has received personal compensation in the range of $10,000-$49,999 for serving as an officer or member of the Board of Directors for McKnight Brain Research Foundation. The institution of Dr. Hamilton has received research support from NIH. The institution of Dr. Hamilton has received research support from Department of Defense. The institution of Dr. Hamilton has received research support from Chan Zuckerberg Initiative.
Harry B. Coslett, MD, FAAN (Univ of Pennsylvania)	The institution of Dr. Coslett has received research support from NIDCD, NINDS, NIA. Dr. Coslett has received publishing royalties from a publication relating to health care.
	No disclosure on file
Ravindar Reddy Geereddy, MD	No disclosure on file

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