What is the role of neuroimaging in dementia? A review

Abstract

• Structural brain imaging is recommended in patients with dementia by all current guidelines. • Brain imaging cannot diagnose dementia but can suggest the most likely underlying neuropathology in a demented patient. • Alzheimer's disease is the commonest cause of dementia and usually co-exists with other pathologies, most often cerebrovascular disease. • Frontotemporal dementias are a heterogeneous group of neuropathologies that typically cause asymmetric frontal, anterior temporal and/or insular atrophy. • Dementia with Lewy bodies is caused by the same pathology as Parkinson's disease, and there is clinical overlap. • Cerebrovascular disease is associated with vascular risk factors, increases linearly with age and, typically, is manifest as white matter ischaemic change and/or lacunar infarcts. • There are no currently available disease-modifying treatments for dementia. • The prevalence of dementia is doubling every 20 years, as people live longer and health and social care resources will soon become insufficient. The worldwide prevalence of dementia is estimated to be 36.5 million with an additional 7.7 million new cases every year. In the UK alone, the prevalence is close to a million. Dementia continues to have huge implications for health and social care. Even in affluent societies like the UK, the needs will soon outstrip available resources. Dementia, defined as a syndrome of progressive memory and cognitive decline that affects the individual in activities of daily life is still fundamentally a clinical diagnosis. However, neuroimaging has increasingly come to play a major role not only in clinical practice but also in research and clinical trials. Current guidelines in the UK recommend structural brain imaging in all patients with a new diagnosis of dementia. Largely, this is to exclude treatable causes like subdural haematoma. However, imaging can also assist in further characterization of certain types of dementia. This article is an update on the various imaging modalities available in current clinical practice in the work-up of dementia in the UK and briefly touches on the newer technologies being explored in dementia research.