Cortical dysfunction in non-demented Parkinson's disease patients: a combined (31)P-MRS and (18)FDG-PET study.
Regional cerebral phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS) was performed in 10 non- demented Parkinson's disease patients and nine age-matched control subjects. Five of the patients undergoing (31)P-MRS and four additional Parkinson's disease patients had cerebral 2-[(18)F]fluoro-2-deoxy-D-glucose PET ((18)FDG-PET), the results of which were compared with those of eight age-matched control subjects. All Parkinson's disease patients underwent neuropsychological testing including performance and verbal subtests of the Wechsler Adult Intelligence Scale-Revised, Boston Naming Test, Controlled Oral Word Association test (FAS Test) and California Learning Test to exclude clinical dementia. (31)P MR spectra from right and left temporo-parietal cortex, occipital cortex and a central voxel incorporating basal ganglia and brainstem were obtained. (31)P MR peak area ratios of signals from phosphomonoesters (PMEs), inorganic phosphate (P(i)), phosphodiesters (PDEs), alpha-ATP, gamma-ATP and phosphocreatine (PCr) relative to beta-ATP were measured. Relative percentage peak areas of PMEs, P(i), PDEs, PCr, and alpha-, beta- and gamma-ATP signals were also measured with respect to the total (31)P-MRS signal. Significant bilateral increases in the P(i)/beta-ATP ratio were found in temporoparietal cortex (P = 0.002 right and P = 0.014 left cortex) for the non-demented Parkinson's disease patients compared with controls. In the right temporoparietal cortex, there was also a significant increase in the mean relative percentage P(i) (P = 0.001). (18)FDG-PET revealed absolute bilateral reductions in glucose metabolism after partial volume effect correction in posterior parietal and temporal cortical grey matter (P < 0.01 and P < 0.05, respectively) for the Parkinson's disease group, using both volume of interest analysis and statistical parametric mapping. There were significant correlations between right temporoparietal P(i)/beta-ATP ratios and estimated reductions in performance IQ (r = 0.96, P < 0.001). Left temporoparietal P(i)/beta-ATP ratios correlated with full scale IQ and verbal IQ (r = -0.82, P = 0.006, r = -0.86, P = 0.003, respectively). In summary, temporoparietal cortical hypometabolism was seen in non-demented Parkinson's disease patients with both (31)P-MRS and (18)FDG-PET, suggesting that both glycolytic and oxidative pathways are impaired. This dysfunction may reflect either the presence of primary cortical pathology or deafferentation of striato-cortical projections. (31)P-MRS and (18)FDG-PET may both provide useful predictors of future cognitive impairment in a subset of Parkinson's disease patients who go on to develop dementia.
Hu
M T
MT
Medical Research Council Cyclotron Unit, Department of Neurosciences, Guys, King's, St Thomas's Hospital Medical School and Institute of Psychiatry, London, UK.
Taylor-Robinson
S D
SD
Chaudhuri
K R
KR
Bell
J D
JD
Labbé
C
C
Cunningham
V J
VJ
Koepp
M J
MJ
Hammers
A
A
Morris
R G
RG
Turjanski
N
N
Brooks
D J
DJ
D000368:Aged; D016022:Case-Control Studies; D003704:Dementia / Q000209:etiology / Q000503:physiopathology; D005260:Female; D019788:Fluorodeoxyglucose F18; D005934:Glucagon / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009778:Occipital Lobe / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology*; D010084:Oxidation-Reduction; D010300:Parkinson Disease / Q000000981:diagnostic imaging / Q000503:physiopathology*; D010759:Phosphorus Isotopes; D013702:Temporal Lobe / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology*; D014055:Tomography, Emission-Computed
D010759:Phosphorus Isotopes; D019788:Fluorodeoxyglucose F18; D005934:Glucagon