Challenges in the diagnosis and management of dementia in Hong Kong.

Dementia affects 47 million people worldwide.1 Persons with dementia require appropriate diagnostic investigations, treatments, and longterm care. The economic impact of dementia is huge. Globally, the total estimated worldwide cost of dementia is US$818 billion.1 In Hong Kong, the estimated number of persons with dementia was 103 433 among those aged 60 years or above in 2009, and this number is projected to increase to 332 688 by 2039.2 Dementia is a clinical syndrome due to a variety of causes. The most common is Alzheimer’s disease (AD) followed by vascular dementia.3 Other causes include dementia with Lewy bodies (DLB), Parkinson’s disease dementia (PDD), and frontotemporal dementia. Clinical diagnosis is often based on clinical features, with reference to the clinical criteria.4-7 Overlap of the clinical features of different dementias is common and may result in an incorrect clinical diagnosis. Notably, recent studies have confirmed the role of structural (magnetic resonance imaging [MRI]), functional ([18F]-2fluoro-2-deoxy-D-glucose positron emission tomography [18FDG-PET] or single-photon emission computed tomography [SPECT]), and amyloid pathology (carbon 11–labelled Pittsburgh compound B) brain imaging in improving the accuracy of clinical differential diagnosis of AD versus other dementia subtypes.4,8,9 For example, volumetric MRI hippocampal volumes differentiate AD from healthy elderly adults with over 80% accuracy. Recently, this has been applied in clinical practice and is preferred to the semiquantitative visual hippocampal assessment that has only 81% sensitivity and 67% specificity for AD diagnosis.4 Furthermore, new amyloid and tau PET neuroimaging for preclinical AD diagnosis will also be available soon for clinical application.9 Compared with AD, DLB and PDD are much less prevalent in Chinese than in Caucasian populations. In this issue of the Hong Kong Medical Journal, Shea et al10 reports a Chinese case series of 16 DLB and seven PDD patients from a memory clinic in Hong Kong. In contrast with the first reported series of 31 DLB and four PDD Chinese patients from Mainland China, which employed clinical assessment only,11 Shea et al10 included functional brain imaging with 18FDG-PET or technetium-99m hexamethylpropylene amine oxime SPECT in the diagnostic assessment, with hypometabolism or Hong Kong Med J 2017;23:218–9 DOI: 10.12809/hkmj175066 LW Chu *, FRCP (Lond, Edin, Glasg), FHKAM (Medicine)