Neurodegenerative Disorders: Classification and Imaging Strategy

Abstract

Clinical scenarios in progressive neurodegenerative diseases encompass a spectrum ranging from (ab)normal aging to dementia and movement disorders. Even during typical aging, there is a variable degree of accumulation of (micro)vascular pathology, amyloid deposition, and Lewy bodies. This reflects partly overlapping risk factors, e.g., for vascular disease and Alzheimer disease (AD). Instead of distinct diseases, there is oftentimes a coexistence of, for example, neurodegenerative AD type pathology and microvascular changes, which might even be supra-additive. Moreover, there is no strict relationship between the underlying pathology and the clinical presentation. For example, the accumulation of Lewy bodies might lead to Parkinson disease (movement disorder) or dementia with Lewy bodies (dementia), and imaging findings for those clinically different conditions may be overlapping and indistinguishable. Additionally, there is a substantial interindividual variability in resilience to disease manifestation or “cognitive reserve,” i.e., the same degree of neurodegeneration may lead to various degrees of clinical symptoms.

As a consequence, dementia syndromes and movement disorders in clinical neuroradiology may be considered as a partially overlapping spectrum of neurodegenerative diseases in terms of clinical presentation, underlying pathology, and imaging findings. Moreover, several types of pathology may potentially coexist. This is fundamentally different to most other domains of neuroradiology, in which patients have in general for example one specific histologic type of tumor, or one type of infection at a time. Consequently, the conclusion of radiology reports in neurodegenerative diseases is therefore often probabilistic rather than uniquely conclusive.

We provide suggestions for the most appropriate radiological techniques and image interpretation strategies for subjects suspected of a neurodegenerative or movement disorder including CT, MRI, PET imaging of glucose metabolism (FDG) and pathological deposits (amyloid and tau) and dopaminergic imaging, as well as an overview of the most important semiquantitative rating scales.

This publication is endorsed by: European Society of Neuroradiology (www.esnr.org)