Side of motor onset is associated with hemisphere-specific memory decline and lateralized gray matter loss in Parkinson's disease.
BACKGROUND
Parkinson's disease (PD) is a neurodegenerative disorder that generally begins with asymmetric motor symptoms that persist over time. This suggests that the dysfunction in the nigrostriatal motor circuit may be lateralized. The present study examined whether the asymmetric motor presentation is associated with hemisphere-specific cognitive decline and lateralized gray matter volume loss.


METHODS
Data from comprehensive cognitive tests that measured visuospatial and verbal functions and high-resolution T1-weighted magnetic resonance images of the brain were acquired in 23 PD subjects with left-side motor symptom onset (PDL), 23 PD subjects with right-side onset (PDR), and 23 matched Controls. GM volume differences were assessed using voxel-based morphometry (VBM). Cognitive results and VBM were compared among the three groups, and correlation analyses were performed between those cognitive domains and brain areas that showed significant differences.


RESULTS
PDL subjects had lower performance on visuospatial memory tasks compared to PDR. Furthermore, PDL subjects experienced lateralized GM loss, which was localized predominantly in the right hemisphere contralateral to the side of motor symptom onset. Visuospatial memory performance in PDL was correlated with GM loss in the right middle frontal gyrus and precuneus.


CONCLUSIONS
These data suggest that the onset of asymmetric motor symptoms in PD may be associated with hemisphere-specific memory decline and lateralized GM loss, particularly in PDL. This study underscores the importance of classifying PD subgroups based on the side of motor symptom onset for clinical care and research to optimize cognitive outcomes.
Department of Neurology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA.
Eun-Young
EY
Lee
Department of Neurology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA.
Suman
S
Sen
Department of Neurology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA; Department of Public Health Sciences, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA; Department of Radiology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA.
Paul J
PJ
Eslinger
Department of Neurology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA.
Daymond
D
Wagner
Department of Public Health Sciences, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA.
Lan
L
Kong
Department of Neurology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA; Department of Pharmacology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA.
Mechelle M
MM
Lewis
Department of Neurology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA.
Guangwei
G
Du
Department of Neurology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA; Department of Pharmacology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA; Department of Radiology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA; Department of Neurosurgery, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA; Department of Kinesiology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA. Electronic address: xuemei@psu.edu.
Xuemei
X
Huang
D000368:Aged; D005260:Female; D066128:Gray Matter / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis* / Q000453:epidemiology / Q000378:metabolism; D008875:Middle Aged; D009044:Motor Cortex / Q000378:metabolism / Q000473:pathology*; D009929:Organ Size; D010300:Parkinson Disease / Q000175:diagnosis* / Q000453:epidemiology / Q000378:metabolism
Cognition; Gray matter volume; Motor asymmetry; Parkinson's disease; Voxel-based morphometry