Atrophy measures can be a visual rating system (Scheltens score) [33], semiautomated, or automated volumetric techniques. Whole-brain and hippocampal atrophy rates are sensitive markers of progression of neurodegeneration and are increasingly used as surrogate outcomes in trials of potentially disease-modifying drugs. Volumetric MRI, along with FDG-PET and high CSF tau, is felt to be a biomarker of neurodegeneration or neuronal injury and could be able to document and follow disease severity [10,34]. In an evidence-based review of dementia diagnosis, the AAN did not recommend routine quantitative volumetry of the hippocampus or the entorhinal cortex because these techniques are labor intensive [9]. Diffusion-weighted imaging/apparent diffusion coefficient [35,36] and magnetization transfer imaging [37] are all either sensitive to early change or can add complementary information to atrophy measures but are second-line imaging tests. HMPAO SPECT or SPECT/CT Brain Regional cerebral blood flow determined using single-photon emission computed tomography (SPECT) imaging with Tc-99m hexamethylpropyleneamine oxime (HMPAO) shows bilateral temporoparietal or hippocampal hypoperfusion in patients with AD. Whether brain SPECT contributes substantially to diagnostic accuracy after a careful clinical examination using current diagnostic criteria is controversial. Although perfusion MRI is promising, SPECT remains superior in identifying pathologic perfusion [38]. An evidence-based review performed by the AAN concluded that SPECT imaging cannot be recommended for either the initial assessment or to clarify the differential diagnosis of suspected dementia because it has not demonstrated superiority to clinical criteria [9]. When compared with FDG-PET, SPECT has a lower diagnostic accuracy and is inferior in its ability to separate healthy controls from patients with true dementia [39,40]. Variant 2: Suspected frontotemporal dementia. Initial imaging. FTD is a neurodegenerative disorder that may be mistaken for AD.
Dementia. Atrophy measures can be a visual rating system (Scheltens score) [33], semiautomated, or automated volumetric techniques. Whole-brain and hippocampal atrophy rates are sensitive markers of progression of neurodegeneration and are increasingly used as surrogate outcomes in trials of potentially disease-modifying drugs. Volumetric MRI, along with FDG-PET and high CSF tau, is felt to be a biomarker of neurodegeneration or neuronal injury and could be able to document and follow disease severity [10,34]. In an evidence-based review of dementia diagnosis, the AAN did not recommend routine quantitative volumetry of the hippocampus or the entorhinal cortex because these techniques are labor intensive [9]. Diffusion-weighted imaging/apparent diffusion coefficient [35,36] and magnetization transfer imaging [37] are all either sensitive to early change or can add complementary information to atrophy measures but are second-line imaging tests. HMPAO SPECT or SPECT/CT Brain Regional cerebral blood flow determined using single-photon emission computed tomography (SPECT) imaging with Tc-99m hexamethylpropyleneamine oxime (HMPAO) shows bilateral temporoparietal or hippocampal hypoperfusion in patients with AD. Whether brain SPECT contributes substantially to diagnostic accuracy after a careful clinical examination using current diagnostic criteria is controversial. Although perfusion MRI is promising, SPECT remains superior in identifying pathologic perfusion [38]. An evidence-based review performed by the AAN concluded that SPECT imaging cannot be recommended for either the initial assessment or to clarify the differential diagnosis of suspected dementia because it has not demonstrated superiority to clinical criteria [9]. When compared with FDG-PET, SPECT has a lower diagnostic accuracy and is inferior in its ability to separate healthy controls from patients with true dementia [39,40]. Variant 2: Suspected frontotemporal dementia. Initial imaging. FTD is a neurodegenerative disorder that may be mistaken for AD.