Glucose Hypometabolism in Hippocampal Subdivisions in Alzheimer's Disease: A Pilot Study Using High-Resolution ¹⁸F-FDG PET and 7.0-T MRI

BACKGROUND AND PURPOSE: Atrophy of the hippocampus is an important clinical diagnostic marker of Alzheimer's disease (AD), and so assessments of hippocampal activity and its subdivisions might provide invaluable information. This study compared the glucose metabolism of hippocampal subdivisions in mild-AD patients and healthy controls. METHODS: High-resolution T2*-weighted gradient-echo magnetic resonance imaging (MRI) images and ¹⁸F-fluorodeoxyglucose (FDG) positron-emission tomography (PET) images were acquired using 7.0-T MRI and high-resolution research tomograph FDG-PET, respectively, in 9 early-stage AD patients and 10 healthy subjects. The hippocampal body was divided into three equal parts (anterior, middle, and posterior), and in each part a region of interest (ROI) was drawn over the cornus ammonis (CA)1, CA2/3, CA4/dentate gyrus (DG), and subiculum. The standardized uptake values of the hippocampal subdivisions were calculated for each ROI as ratios relative to the pons standardized uptake value. Statistical analysis was conducted using the Mann-Whitney U test. RESULTS: Patients with early-stage AD patients showed significantly less metabolic activity than healthy controls focally in the middle (p=0.050) and posterior (p=0.034) CA2/3 regions of the right hippocampus, and significantly less activity throughout the left hippocampal body in the anterior CA2/3 (p=0.027) and CA4/DG (p=0.027) regions, the middle CA1 region (p=0.011), and the posterior CA1 (p=0.034), CA2/3 (p=0.007), and CA4/DG (p=0.014) regions. CONCLUSIONS: It was possible to use high-resolution PET-MRI fusion images to identify hippocampus subdivisions and assess glucose metabolism in the subfields. Reductions in metabolic activity were found to vary along the hippocampal axis in early-stage AD patients.

Hypometabolism based on a cutoff point on the mini-mental state examination in Parkinson’s disease

Objective: The aim of the present study was to evaluate cortical hypometabolism of the F-18- fluorodeoxyglucose positron emission tomography (FDG-PET) based on a diagnostic cutoff point of the mini-mental state examination (MMSE) in de novo PD.Methods: We recruited 24 PD patients and 15 healthy controls to analyze FDG-PET. We divided the patients into two groups by the diagnostic cutoff point of MMSE for diagnosing dementia, with scores of>25 vs. 25. Compared to healthy controls, patients with a MMSE> 25 and 25 and < 25 was found in the right inferior parietal lobule. Conclusions: In the comparison by cutoff point of MMSE (25/24), hypometabolism in the right inferior parietal lobule suggests that the posterior cortical deficit is the main region ofde novo PD with cognitive impairment. Hypometabolism of right inferior parietal lobule is related to the damage of cerebral networkin de novo PD.

A case of Posterior Cortical Atrophy Presenting with Features of Atypical Dementia

Posterior cortical atrophy(PCA) is a presenile dementia that presents primarily with signs and symptoms of cortical visual dysfunction, while memory is relatively preserved until the late stage of the disease. We report a patient with PCA, confirmed by brain magnetic resonance imaging (MRI) and F18-fluorodeoxyglucose positron emission tomography(FDG PET). A 58-year-old right-handed woman presented initially with visual dimness and difficulty finding things around her. She had partial Balint's syndrome, partial Gerstmann syndrome, and idiomotor apraxia. She also had a mild memory disturbance, but preserved insight of her disease. Neuropsychological evaluation showed decreased parietal and left temporal functions bilaterally. Brain MRI and F18-FDG PET revealed typical bilateral occipitoparietal atrophy and hypometabolism, which were slightly worse on the right side. Cholinesterase inhibitor administration for 6 months improved the memory impairment slightly, but not the cortical visual dysfunction. This is a typical case of PCA, confirmed by neurologic signs and imaging findings.

The Clinical Findings of Unitemporal and Bitemporal Glucose Hypometabolism in Mesial Temporal Lobe Epilepsy / 대한간질학회지

PURPOSE: To identify clinical characteristics in patients with unitemporal hypometabolism (UTH) or bitemporal hypometabolism (BTH) in mesial temporal lobe epilepsy (TLE). METHODS: We enrolled 95 patients with mesial TLE, 87 of whom subsequently had a surgery. Seizures, interictal and ictal EEG, brain MRI, Wada test, and neuropsychological test results were reviewed. (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) scans were visually interpreted. Patients were divided into two groups, UTH and BTH. RESULTS: There were 59 UTH patients and 36 BTH patients. Semiology showed that UTH had higher frequencies of aura and unilateral dystonic posturing than BTH, whereas BTH had higher frequencies of a non-lateralized bilateral ictal EEG pattern and of bilateral interictal spikes than UTH. Moreover, BTH had symmetric Wada memory scores more frequently than UTH, and white matter changes of the bilateral temporal lobes in brain MRI were more frequent in BTH than UTH. All UTH patients with bilateral TLE in scalp EEG showed unilateral seizure onset in intracranial EEG. CONCLUSION: The characteristic clinical findings of mesial TLE patients with BTH were more frequent non-lateralized ictal EEG pattern, bitemporal interictal spikes, symmetric Wada memory score, the presence of anterior temporal white matter changes, and less frequent aura, and unilateral dystonic posturing. Surgical outcomes were similar and good in both groups although surgery could not be performed in 8 (22.2%) BTH patients.

Correlation of FDG PET Hypometabolism with Interictal Spike Frequency during FDG Distribution Phase in Temporal Lobe Epilepsy

BACKGROUND: Although hypometabolism of positron emission tomography (PET) helps lateralization of epileptic focus in temporal lobe epilepsy (TLE), the mechanism of PET hypometabolism (PET-Hypo) is still controversial. We investigated whether interictal spike frequency during distribution phase of 18F-fluorodeoxyglucose (DP-FDG) correlates with the degree of PET-Hypo in TLE. METHODS: FDG PET was performed in 21 TLE patients. In PET, polar, mesial, anterior, middle and posterior temporal ROIs (region of interests) were determined in superior, middle and inferior transtemporal planes. PET Asymmetry index (AI) of each ROI was obtained by (right-left)/(right+left) x 2. Scalp EEG was recorded from 30 min prior to FDG injection until the end of scanning. Interictal spikes on temporal electrodes (F7, F8, FT9, FT10, T3, T4, T5 and T6) were counted during DP-FDG. Left-Right difference of spike numbers on electrodes of both temporal regions was obtained by subtracting spike number of right temporal region from that of left side. RESULTS: Average number of interictal spikes during FDG-DP was 11.5 per patient. Distributions of spikes were anterior temporal (F7, F8, FT9, FT10):70.7%, mid-temporal (T3,T4):29.3%, posterior temporal (T5,T6):0%. Left-Right difference of spike number was strongly correlated with PET AI of whole temporal region (r=0.655, p=0.002). Lateralization of all PET-Hypo was concordant to that of interictal spike dominance during DP-FDG although 2 cases showed false lateralization of epileptic focus by PET. CONCLUSIONS: FDG PET hypometabolism was significantly correlated with DP-FDG interictal spike numbers. Anterior and polar temporal regions showed the best correlation. PET-Hypo may reflect not only permanent functional deficit but also transient regional cerebral dysfunction.