Neuroimaging in Dementia

Adam M. Staffaroni, PhD; Fanny M. Elahi, MD, PhD; Dana McDermott, DO; Kacey Marton, MS; Elissaios Karageorgiou, MD, PhD; Simone Sacco, MD; Matteo Paoletti, MD; Eduardo Caverzasi, MD; Christopher P. Hess, MD, PhD; Howard J. Rosen, MD; Michael D. Geschwind, MD, PhD

Disclosures

Semin Neurol. 2017;37(5):510-537. 

In This Article

Abstract and Introduction

Abstract

Although the diagnosis of dementia still is primarily based on clinical criteria, neuroimaging is playing an increasingly important role. This is in large part due to advances in techniques that can assist with discriminating between different syndromes. Magnetic resonance imaging remains at the core of differential diagnosis, with specific patterns of cortical and subcortical changes having diagnostic significance. Recent developments in molecular PET imaging techniques have opened the door for not only antemortem but early, even preclinical, diagnosis of underlying pathology. This is vital, as treatment trials are underway for pharmacological agents with specific molecular targets, and numerous failed trials suggest that earlier treatment is needed. This article provides an overview of classic neuroimaging findings as well as new and cutting-edge research techniques that assist with clinical diagnosis of a range of dementia syndromes, with an emphasis on studies using pathologically proven cases.

Introduction

The diagnosis of dementia is becoming increasingly reliant on a broad range of neuroimaging techniques, and this is reflected in several updated diagnostic criteria.[1,2] Neuroimaging enhances the accuracy of diagnoses for distinct dementia subtypes. The recent failures of treatment trials for Alzheimer's disease (AD)[3] indicate that earlier intervention, and therefore earlier diagnosis, may be critical to treatment success. Early diagnosis can be facilitated by neuroimaging techniques that can detect the earliest pathological and metabolic alterations that occur in neurodegenerative disease.

In this review, we discuss clinically relevant neuroimaging findings in a wide range of dementia syndromes, as well as cutting-edge techniques that are gaining traction in research. As we move toward the age of treatments designed for specific molecular targets (e.g., tau and amyloid), there is a growing need to move beyond simply classifying syndromes based entirely on clinical phenotypes to predicting underlying pathologies with greater precision using imaging, genetic, cerebrospinal fluid (CSF), and other objective markers of disease. In this review, we try to distinguish between imaging findings in pathologically proven versus clinically based diagnoses, placing particular emphasis on neuroimaging in pathologically confirmed cases as well as longitudinal neuroimaging studies. Dementia and related syndromes discussed in this review include AD, the frontotemporal dementia (FTD) spectrum, primary progressive aphasias (PPA), vascular dementia (VaD), Lewy body disease (LBD) and Parkinson's disease dementia (PDD), rapidly progressing dementias (RPD), normal pressure hydrocephalus (NPH), and cerebellar disorders. Other dementing conditions, including neurodegeneration with brain iron accumulation (NBIA) and chronic traumatic encephalopathy (CTE), are not covered here to allow for a greater depth of coverage of the more common and established causes of dementia. We conclude with a review of neuroimaging biomarkers of neurodegenerative diseases that are being developed in research, with a focus on structural and functional connectivity.

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