Nuclear medicine imaging in dementia: a practical overview for hospitalists

Dementia is a clinical syndrome with diverse presentation, a challenging differential diagnosis, and time-sensitive therapy. The most common cause of dementia in patients aged > 65 years is Alzheimer's disease, which now affects 4 million people in the United States, but is often underrecognized, especially in the inpatient population. The hospitalist may have the opportunity to evaluate a patient's initial presentation of dementia. Addressing the inpatient's dementia symptoms can improve overall care and outcomes, so it is imperative that the hospitalist is abreast of recent developments in the dementia workup. The focus of this article is to overview how nuclear medicine imaging of the brain can aid in this process, with perfusion single-photon emission computed tomography (SPECT) and fludeoxyglucose F 18 ((18)F-FDG) positron emission tomography (PET) as the 2 most common modalities. Our discussion focuses on Alzheimer's disease, as this the most common etiology of dementia in patients aged > 65 years; however, we also touch on the other common neurodegenerative dementias (eg, dementia with Lewy bodies, vascular dementia, and frontotemporal dementia) for completeness. We begin with a summary of the most recent published guidelines for each of these neurodegenerative diseases, and then expand on the role that nuclear imaging plays in each. We provide a basic overview of the principles of these nuclear medicine techniques, and then illustrate findings in perfusion SPECT and (18)F-FDG PET for typical patterns of dementia, with emphasis on evidence regarding diagnostic accuracy of each modality, in comparison with accepted gold standards. Finally, we outline some future research topics within the field of nuclear medicine in dementia, including amyloid plaque imaging and dopamine transporter imaging.