Diagnostic imaging of dementia with Lewy bodies, frontotemporal lobar degeneration, and normal pressure hydrocephalus.

Neuroimaging can provide important biomarkers and is very useful for supporting dementia diagnosis. This review summarizes the neuroimaging findings of dementia with Lewy bodies (DLB), frontotemporal lobar degeneration (FTLD), and normal pressure hydrocephalus (NPH). In DLB, medial temporal atrophy is milder than that of Alzheimer's disease. 2-fluoro-2-deoxy-D-glucose-positron emission tomography and brain perfusion single-photon emission computed tomography demonstrate hypometabolism and hypoperfusion in the occipital lobe, in addition to decreased metabolism and perfusion in the parietotemporal, posterior cingulate, precuneus, and frontal association cortices. The cingulate island sign, which shows relatively spared middle-to-posterior cingulate cortex metabolism compared with precuneus hypometabolism, is proposed to detect DLB in 2-fluoro-2-deoxy-D-glucose-positron emission tomography imaging. Reduced uptake in dopamine transporter imaging and reduced myocardial uptake in iodine-123 metaiodobenzylguanidine cardiac scintigraphy are indicative biomarkers for DLB diagnosis. Characteristic findings of FTLD include dominant frontotemporal atrophy, hypometabolism, and hypoperfusion. Most idiopathic NPH cases demonstrate disproportionally enlarged subarachnoid space hydrocephalus findings, including dilated ventricular systems, enlarged Sylvian fissures, tight sulci in the midline, and a high convexity.