Diffuse occipital hypometabolism on [18 F]-FDG PET scans in patients with idiopathic REM sleep behavior disorder: prodromal dementia with Lewy bodies?
BACKGROUND
Previous longitudinal studies have revealed that specific patterns on [(18) F]-fluoro-d-glucose (FDG) positron emission tomography (PET) scans in patients with amnesic mild cognitive impairment can predict Alzheimer's disease (AD). However, the significance of particular patterns on [(18) F]-FDG PET scans in prodromal patients with dementia with Lewy bodies (DLB) remains unclear.


METHODS
Based on the prevailing evidence that rapid eye movement (REM) sleep behavior disorder (RBD) often precedes the onset of DLB, [(18) F]-FDG PET scans of nine non-demented patients reporting recurrent nocturnal dream-enactment behavior in our memory clinic were compared with the normative database using three-dimensional stereotactic surface projection (3D-SSP) images. All patients underwent clinical and neuropsychological examinations as well as cardiac [(123) I]-metaiodobenzylguanidine ([(123) I]-MIBG) scintigraphy.


RESULTS
Four patients were found to have diffuse areas of reduced cerebral metabolic rate of glucose (CMRglc), predominantly in the occipital lobe, which is the preferentially affected region in DLB patients. In contrast, five patients showed no such occipital hypometabolism; instead, these five patients showed hypometabolism in the left anterior cingulate gyrus (Broadmann area (BA) 24), right frontal lobe (BA 32) and right anterior temporal lobe (BA 38), which are the preferentially affected regions in Parkinson's disease rather than DLB. The extent of the reduction in CMRglc in the left occipital lobe was correlated with scores on the Bender Gestalt Test, which reflects visuospatial ability, but not with global cognitive measures. All patients showed reduced cardiac [(123) I]-MIBG levels, consistent with underlying Lewy body disease.


CONCLUSIONS
These variations in [(18) F]-FDG PET scans raise the possibility that the specific pattern of CMRglc reduction may predict developing DLB in patients with idiopathic RBD. Further follow-up studies are needed, particularly on patients with diffuse occipital hypometabolism.
Fujishiro
Hiroshige
H
PET/CT Dementia Research Center, Juntendo Tokyo Koto Geriatric Medical Center, Juntendo University School of Medicine, Tokyo, Japan. fujishiro17@hotmail.co.jp
Iseki
Eizo
E
Murayama
Norio
N
Yamamoto
Ryoko
R
Higashi
Shinji
S
Kasanuki
Koji
K
Suzuki
Masaru
M
Arai
Heii
H
Sato
Kiyoshi
K
D019797:3-Iodobenzylguanidine; D000368:Aged; D004292:Dominance, Cerebral / Q000502:physiology; D042241:Early Diagnosis; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D019788:Fluorodeoxyglucose F18; D005625:Frontal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology; D006179:Gyrus Cinguli / Q000000981:diagnostic imaging / Q000503:physiopathology; D006321:Heart / Q000294:innervation; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007457:Iodine Radioisotopes; D020961:Lewy Body Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008297:Male; D009483:Neuropsychological Tests; D009778:Occipital Lobe / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D049268:Positron-Emission Tomography; D020187:REM Sleep Behavior Disorder / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D011877:Radionuclide Imaging; D013223:Statistics as Topic; D013564:Sympathetic Nervous System / Q000503:physiopathology; D013702:Temporal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology
D007457:Iodine Radioisotopes; D019788:Fluorodeoxyglucose F18; D019797:3-Iodobenzylguanidine