Neuroimaging studies in the evaluation of dementia
- Norman Relkin, MD, PhD
Norman Relkin, MD, PhD
- Associate Professor of Neurology
- Director, Memory Disorders Program
- Weill Cornell Medical College, NY
Neuroimaging is most informative when performed as part of a comprehensive dementia evaluation that includes review of the history and medications, a physical examination (including neurologic and psychiatric components), and assessment of cognitive, functional, and behavioral status. This is supplemented in selected cases by blood and urine tests, cerebrospinal fluid analysis, electroencephalography, and other procedures. In this context, neuroimaging provides unique and valuable information that complements the other elements of a dementia evaluation.
Neuroimaging can be divided into structural, functional, and molecular categories. Structural brain imaging studies are generally considered routine parts of dementia evaluations and may be repeated at a later time point for clarification of diagnosis. More specialized functional and molecular imaging studies are performed in selected patients when additional diagnostic information is required.
Diagnostic criteria for Alzheimer disease (AD) and other neurodegenerative disorders acknowledge the existence of precursor states to symptomatic dementia, such as mild cognitive impairment (MCI) and preclinical stages, which lack overt clinical symptoms but can be identified on the basis of biomarkers and imaging evidence [1,2]. In this context, neuroimaging has taken on new importance as an objective means of documenting some of the earliest manifestations of dementia pathology.
Structural, functional, and molecular imaging techniques in dementia will be reviewed here. The clinical presentation and diagnosis of mild cognitive impairment and dementia are discussed elsewhere. (See "Mild cognitive impairment: Epidemiology, pathology, and clinical assessment" and "Evaluation of cognitive impairment and dementia".)
Additional topics relevant to the diagnosis of specific forms of dementia include:
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- STRUCTURAL NEUROIMAGING
- Indications for structural imaging
- - Computed tomography versus magnetic resonance imaging
- - Use of contrast
- Structural imaging findings
- - Cerebral atrophy
- - Hippocampal atrophy
- - Cerebrovascular disease
- - Microhemorrhage
- - Ventriculomegaly
- - Altered brain diffusivity
- FUNCTIONAL AND MOLECULAR NEUROIMAGING
- Functional imaging modalities
- - Techniques
- - Parameters
- Cerebral perfusion
- Regional glucose metabolism
- Molecular imaging modalities
- - Striatal dopamine transporter imaging
- - Amyloid imaging
- - Magnetic resonance spectroscopy
- Indications for functional and molecular imaging
- Functional imaging findings
- - Alzheimer disease
- - Dementia with Lewy bodies
- - Frontotemporal dementia
- Molecular imaging findings