Should neuroimaging be obtained in the work-up of neurocognitive decline?

From the Guidelines

Yes, neuroimaging should be obtained in the work-up of neurocognitive decline. Brain imaging, typically starting with a non-contrast CT scan or MRI, is an essential component of the evaluation to identify potential structural causes of cognitive impairment. MRI is generally preferred when available as it provides better visualization of brain tissue, white matter changes, and subtle abnormalities, as noted in the study by 1. Imaging can detect treatable conditions such as normal pressure hydrocephalus, brain tumors, subdural hematomas, or cerebrovascular disease that may contribute to cognitive symptoms. It also helps distinguish between different types of neurodegenerative disorders, as certain patterns of atrophy may suggest specific diagnoses like Alzheimer's disease (hippocampal atrophy) or frontotemporal dementia (frontal and temporal lobe atrophy), as discussed in the study by 1.

The primary role of neuroimaging in the workup of patients with probable or possible AD has typically been to exclude other significant intracranial abnormalities, as stated in the study by 1. A noncontrast MRI examination will assist with the diagnosis of dementia by excluding structural pathology like tumors or subdural hematomas. The American Academy of Neurology (AAN) has recommended that the routine use of structural neuroimaging, such as a noncontrast CT or MRI examination, may assist with the diagnosis of dementia, as mentioned in the study by 1.

The timing of neuroimaging should be early in the evaluation process, particularly for patients with rapid decline, focal neurological signs, history of trauma, or onset before age 65. While not all causes of cognitive decline will show visible changes on imaging, the information gained helps guide treatment decisions and provides prognostic information for patients and families. Neuroimaging results should be interpreted alongside clinical history, cognitive testing, and laboratory studies for a comprehensive assessment, as recommended in the study by 1.

Some key points to consider when using neuroimaging in the work-up of neurocognitive decline include:

• MRI is preferred over CT due to its higher sensitivity to vascular lesions and certain subtypes of dementia, as noted in the study by 1.
• The use of semi-quantitative scales for routine interpretation of both MRI and CT scans, including the medial temporal lobe atrophy (MTA) scale, Fazekas scale, and global cortical atrophy (GCA), is recommended, as stated in the study by 1.
• Advanced MR sequences, such as rs-FMRI, MR spectroscopy, diffusion tensor imaging (DTI), and arterial spin labelling (ASL), are not recommended for routine clinical use, but may be useful in a research setting or if access to advanced expertise is present, as mentioned in the study by 1.

From the Research

Neuroimaging in Neurocognitive Decline

• Neuroimaging plays a crucial role in the evaluation and management of neurodegenerative cognitive/dementia syndrome, as stated in 2.
• The use of structural imaging, such as magnetic resonance imaging (MRI) or computed tomography (CT), is recommended as a first-tier approach to improve diagnostic confidence and assess for nonneurodegenerative treatable conditions 2.
• Molecular methods, such as fluorodexoyglucose positron emission tomography (PET), can provide more diagnostic specificity and help differentiate between atypical Alzheimer's disease and frontotemporal dementia 2.

Imaging Modalities

• Various imaging modalities, including structural and functional MRI, PET, and single-photon emission computed tomography, have shown characteristic changes in the brains of patients with Alzheimer's disease and other neurodegenerative diseases 3, 4.
• The combination of imaging biomarkers can help facilitate diagnosis, disease staging, and the development of effective disease-modifying therapies 3, 5.
• Advanced neuroimaging tests, such as diffusion tensor imaging, functional MRI, and magnetic resonance spectroscopy, can provide additional information on neural correlates of cognitive dysfunction 5, 6.

Clinical Utility

• Neuroimaging is an essential tool for the early diagnosis of neurodegenerative diseases in both clinical and research settings 4, 6.
• The use of different neuroimaging modalities together may lead to the identification of an early diagnostic and/or prognostic biomarker for Alzheimer's disease 5.
• Neuroimaging can help identify underlying causes of cognitive disorders, including Alzheimer's disease, Lewy body disease, cerebrovascular disease, and frontotemporal degeneration 6.