Default mode network differences between rigidity- and tremor-predominant Parkinson's disease.
Parkinson's disease (PD) traditionally is characterized by tremor, rigidity, and bradykinesia, although cognitive impairment also is a common symptom. The clinical presentation of PD is heterogeneous and associated with different risk factors for developing cognitive impairment. PD patients with primary akinetic/rigidity (PDAR) are more likely to develop cognitive deficits compared to those with tremor-predominant symptoms (PDT). Because cognitive impairment in PD appears to be related to changes in the default mode network (DMN), this study tested the hypothesis that DMN integrity is different between PDAR and PDT subtypes.



Resting state fMRI (rs-fMRI) and whole brain volumetric data were obtained from 17 PDAR, 15 PDT and 24 healthy controls (HCs) using a 3T scanner. PD patients were matched closely to HCs for demographic and cognitive variables, and showed no symptoms of dementia. Voxel-based morphometry (VBM) was used to examine brain gray matter (GM) volume changes between groups. Independent component analysis (ICA) interrogated differences in the DMN among PDAR, PDT, and HC.



There was decreased activity in the left inferior parietal cortex (IPC) and the left posterior cingulate cortex (PCC) within the DMN between PDAR and both HC and PDT subjects, even after controlling for multiple comparisons, but not between PDT and HC. GM volume differences between groups were detected at a lower threshold (p < 0.001, uncorrected). Resting state activity in IPC and PCC were correlated with some measures of cognitive performance in PD but not in HC.



This is the first study to demonstrate DMN differences between cognitively comparable PDAR and PDT subtypes. The DMN differences between PD and HC appear to be driven by the PDAR subtype. Further studies are warranted to understand the underlying neural mechanisms and their relevance to clinical and cognitive outcomes in PDAR and PDT subtypes.
Radiology, Center for NMR Research, Penn State University College of Medicine, Hershey, PA, USA; Neural & Behavioral Sciences, Penn State University College of Medicine, Hershey, PA, USA. Electronic address: pkarunanayaka@hmc.psu.edu.
Prasanna R
PR
Karunanayaka
Neurology, Penn State University-Milton S. Hershey Medical Center, Hershey, PA, USA.
Eun-Young
EY
Lee
Neurology, Penn State University-Milton S. Hershey Medical Center, Hershey, PA, USA; Pharmacology, Penn State University-Milton S. Hershey Medical Center, Hershey, PA, USA.
Mechelle M
MM
Lewis
Neurology, Penn State University-Milton S. Hershey Medical Center, Hershey, PA, USA.
Suman
S
Sen
Radiology, Center for NMR Research, Penn State University College of Medicine, Hershey, PA, USA; Neural & Behavioral Sciences, Penn State University College of Medicine, Hershey, PA, USA; Neurology, Penn State University-Milton S. Hershey Medical Center, Hershey, PA, USA.
Paul J
PJ
Eslinger
Radiology, Center for NMR Research, Penn State University College of Medicine, Hershey, PA, USA; Neurosurgery, Penn State University-Milton S. Hershey Medical Center, Hershey, PA, USA.
Qing X
QX
Yang
Radiology, Center for NMR Research, Penn State University College of Medicine, Hershey, PA, USA; Neurology, Penn State University-Milton S. Hershey Medical Center, Hershey, PA, USA; Pharmacology, Penn State University-Milton S. Hershey Medical Center, Hershey, PA, USA; Neurosurgery, Penn State University-Milton S. Hershey Medical Center, Hershey, PA, USA; Kinesiology, Penn State University-Milton S. Hershey Medical Center, Hershey, PA, USA.
Xuemei
X
Huang
D000328:Adult; D000368:Aged; D001931:Brain Mapping; D003072:Cognition Disorders / Q000209:etiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000502:physiology*; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000150:complications / Q000503:physiopathology*; D012146:Rest / Q000502:physiology; D014202:Tremor / Q000209:etiology / Q000503:physiopathology*
Cognitive impairment; Independent component analysis (ICA); Parkinson's disease; Resting state fMRI