FDG-PET findings in fronto-temporal dementia: A case report and review of literature.

Fronto-temporal lobar degeneration (FTLD) is a clinically and pathologically heterogeneous syndrome, characterized by progressive decline in behavior or language associated with degeneration of the frontal and anterior temporal lobes. Three distinct clinical variants of FTLD have been described. Despite the difficulties, accurate diagnosis is critical because the clinical management differs for Alzheimer's disease (AD) and FTLD. Positron emission tomography with fluro-deoxy-glucose (FDG-PET) typically shows sufficient abnormalities that can be used to improve the accuracy of distinguishing AD from FTLD in individual cases. Though temporo-parietal hypometabolism is sensitive in diagnosis of AD, it is less specific. The importance of evaluating the cingulate and anterior temporal cortices for arriving at a diagnosis of FTLD is stressed.

Crossed cerebellar diaschisis on F-18 FDG PET/CT.

Diaschisis is the inhibition of function produced by focal disturbances in a portion of the brain at a distance from original site of injury. Many studies using brain SPECT (single-photon emission computed tomography) have demonstrated crossed cerebellar diaschisis (CCD) in patients with cerebral cortical infarct. We report a case of cerebrovascular accident involving the left middle cerebral artery territory. PET/CT performed one month after stroke showed hypometabolism in the left cerebral hemisphere with hypometabolism of the contralateral cerebellum. The finding of diminished glucose metabolism in the contralateral cerebellum represents CCD.

Utility of high fat and low carbohydrate diet in suppressing myocardial FDG uptake.

INTRODUCTION: Fluoro-deoxy-glucose (FDG) can be used to visualize inflammation in atherosclerotic plaques in coronary arteries, if myocardial FDG uptake is adequately suppressed. Prolonged fasting for suppressing myocardial FDG uptake is inconsistent. We evaluated the feasibility to consistently suppress myocardial FDG uptake with a low carbohydrate high fat protein permitted (LCHFPP) diet. MATERIALS AND METHODS: This was a prospective study. 50 patients were included in fasting group (>12 hours fasting) and 60 patients were included into LCHFPP diet. Fasting group had no special dietary preparation. Patients in LCHFPP diet group were asked to consume LCHFPP diet the night before and 4 hours prior to the study. Visual analysis of myocardial FDG uptake was done on maximum intensity projection image. Using CT images for localization, the ability to delineate possible FDG uptake in the left coronary artery was assessed in the corresponding PET image and the studies were classified as "interpretable" or "Not interpretable". RESULTS: 60 patients (mean age 47 years) from LCHFPP diet group and 50 patients (mean age 49.9 years) from fasting group were included. None of the patients were known diabetics. The mean blood glucose level was 96 mg/dL. Forty-eight patients had consumed LCHFPP diet as per protocol. Twelve had consumed LCHFPP diet only on the night before the study (non-compliant). The average duration of fasting in compliant patients was 5.9 ± 0.9 hours in the diet group and 14.6 hours in fasting group. In LCHFPP diet group, the myocardial FDG uptake was classified as complete suppression in 31; minimal uptake in 15; moderate inhomogenous uptake in 8 and homogenous intense uptake in 6 patients. Fifty-four of the 60 patients had interpretable study. When non-compliant patients were excluded, 84% of the patients had significant FDG uptake suppression and 94% of the studies were classified as interpretable. In the fasting group, complete myocardial suppression of FDG uptake was noticed in 16; minimal in 8; moderate inhomogenous in 15; and homogenous intense in 11 patients. 27 patients (54%) had interpretable study. CONCLUSION: Consistent and significant myocardial FDG uptake suppression is possible in most patients using LCHFPP diet. The LCHFPP diet, if taken as per protocol, leads to consistent myocardial FDG uptake suppression to allow for adequate evaluation of the left coronary artery inflammation in nearly all the patients. LCHFPP diet is also significantly more efficacious than prolonged (>12 hours) fasting protocol in suppressing myocardial FDG uptake.