Ultrahigh Field Nigrosome 1 Imaging of REM Behavior Disorder (S36.004)

Objective: • To evaluate N1 using ultrahigh field imaging in a cohort with RBD compared to PD and healthy controls and correlate N1 intensity with various clinical measures Background: • The dopamine neurons that degenerate first in Parkinson’s disease (PD) are in nigrosome 1 (N1). N1 can be visualized using magnetic resonance imaging (MRI). Previous studies have identified differences in N1 signal between individuals with manifest PD and healthy controls. Few studies have investigated N1 in individuals with rapid eye movement (REM) behavior disorder (RBD).These studies have qualitatively evaluated for loss of hyperintensity (the ‘swallowtail’ sign) within N1 and have reported a wide range of proportions of abnormalities (27–77%). Design/Methods: • Each subject was sex- and age-matched (+/−3 years). Each subject submitted to the Montreal Cognitive Assessment (MoCA), Brief Identification of Smell Test (BSIT), Unified Parkinson Disease Rating Scale part three (UPDRS3), and Scales for Outcomes in Parkinson's disease - Autonomic Dysfunction (SCOPA-AUT). Each subject also underwent susceptibility-weighted MRI at 7T. N1 was manually drawn by a neurologist blinded to subject's clinical status with the borders defined according to previously published reports. Signal intensities within N1 were normalized to the non-N1 region of the substantia nigra. Results: • We recruited 14 healthy control subjects, 27 subjects with RBD, and 11 subjects with early stage PD.Six RBD subjects were excluded due to uninterpretable MRIs. Qualitatively, 13/14 healthy controls, 6/20 RBD subjects, and 0/11 PD subjects exhibited a ‘swallowtail’ sign. The mean intensity of N1 was 1.62, 1.38, and 1.19 for HC, RBD, and PD subjects, respectively (p=0.0001). Correlations of N1 intensity with MoCA, BSIT, and UPDRS3 approached significance (p=0.06, p=0.06, and p=0.16, respectively) whereas correlation with SCOPA-AUT was statistically significant (p=0.02). Conclusions: Evaluation of N1 using ultrahigh field imaging may add prognostic value in predicting phenoconversion. Longitudinal studies are needed. Disclosure: Dr. Neilson has received personal compensation in the range of $5,000-$9,999 for serving as an Expert Witness for Hart Wagner LLP. Dr. Neilson has received research support from VA ORD - Clinical Science Research and Development. An immediate family member of Dr. Neilson has received research support from NIH - NINDS. Dr. Elliott has nothing to disclose. Mrs. Dennis has nothing to disclose. Dr. Brodsky has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for Medtronic. The institution of Dr. Brodsky has received research support from Boston Scientific. Dr. Lim has received personal compensation in the range of $10,000-$49,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Applied Cognition. Dr. Lim has stock in Applied Cognition. The institution of Dr. Lim has received research support from NIH. The institution of Dr. Lim has received research support from VA. The institution of Dr. Lim has received research support from Department of Defense. The institution of Dr. Lim has received research support from National Science Foundation. Dr. Lim has received publishing royalties from a publication relating to health care.