FDG PET Scan for Diagnosis of Lewy Body Dementia

Diagnostic Approach for Lewy Body Dementia

The American College of Radiology recommends structural brain imaging with MRI (preferred) or CT to exclude other causes of cognitive impairment in patients with suspected Lewy Body Dementia (DLB) 3, 4
Clinical evaluation by a cognitive disorders specialist is necessary before proceeding to advanced imaging for patients with suspected DLB 1, 2
The American College of Radiology suggests that FDG PET is recommended when the underlying pathological process remains unclear after baseline clinical and structural imaging evaluation for patients with suspected DLB 1, 5

FDG PET shows characteristic patterns in DLB, including generalized low uptake with occipital hypometabolism, and relative preservation of posterior or midcingulate metabolism (the "cingulate island sign") 1, 2

The diagnostic algorithm for DLB involves completing baseline clinical evaluation and structural brain imaging (MRI preferred), and if diagnosis remains unclear, obtaining an FDG PET scan as the next diagnostic step 1, 3, 4, 5

The American College of Radiology prefers FDG PET before proceeding to [123 I]-Ioflupane SPECT (DaTscan) due to cost considerations and high probability of establishing the diagnosis for patients with suspected DLB 1, 2
FDG PET measures cellular glucose metabolism, which is reduced in DLB with a specific topographic pattern consistent with the neurologic localization of symptoms 5
The interpretation of FDG PET should consider the patient's clinical presentation and risk profile for accurate diagnosis of DLB 5