Clinical Differences among Four Common Dementia Syndromes
Cases of dementia are increasing due to longer life expectancy of the world population. Physicians should be able to recognize common dementia syndromes. After excluding reversible causes of dementia, there are four common dementia syndromes, which are Alzheimer’s disease, vascular dementia, dementia with Lewy body, and frontotemporal dementia. The key points of clinical differences of these dementia syndromes are summarized in this article.
Key words: Alzheimer’s disease, vascular dementia, dementia with Lewy body, frontotemporal dementia, Parkinson’s disease.
Introduction
There are four clinical dementia syndromes accounting for 90% of all cases after excluding other common reversible causes of cognitive impairment.1 These four major diseases are Alzheimer’s disease (AD) and vascular dementia (VaD), which together account for approximately 80% of dementias, dementia with Lewy body (DLB), and frontotemporal dementia (FTD). The four common diseases have different clinical characteristics, and there are diagnostic criteria for each of them. These criteria bear review as physicians who deal with dementia might not always recall them in detail. As AD is the most common cause of dementia, accounting for 50-60% of cases, physicians should be familiar with the clinical difference between AD and other diseases.2,3 This article will focus on the clinical difference between AD and other common dementia syndromes.
Alzheimer’s Disease
A 70-year-old man presented with a 3-year history of progressive memory loss, which mainly affected his short term memory. He needed his daughter to remind him of his appointments and some day-to-day activities. He had problems with driving alone as he became confused with the routes, though he had used them for a long time. He could not manage his bills as usual. The physical examination was unremarkable. The Mini Mental State Examination (MMSE) was 20 out of 30.
Alzheimer’s disease is the most common cause of dementia among older adults. The major pathogenesis is the production and accumulation of beta-amyloid peptide, bringing about the formation of neurofibrillary tangles, oxidation and lipid peroxidation, glutaminergic excitotoxicity, inflammation, and activation of the cascade of apoptotic cell death. Furthermore, the other hypothesis regarding the pathophysiology of AD stresses tau-protein abnormalities, heavy metals, vascular factors, and viral infections.4 The natural course of AD averages 10 years. The cardinal features are insidious onset, progressive course, and early memory loss; at least one other cognitive impairment such as language dysfunction, apraxia, agnosia, visuospatial disorder, as well as executive dysfunction, must be seen. These impairments should constitute a decline from the previous level of cognitive functioning, interfering with daily activities.
Memory decline is the hallmark of cognitive change in AD. It is characterized as a storage deficit, meaning that material cannot be recalled with cue. In the early stage, memory impairment for recent events is common whereas long-term memory remains intact. As the disease progresses, individuals with AD are increasingly unable to recall more distant memories. Typically, the motor signs are absent early in the course. Likewise, sensory abnormalities, seizures, and gait difficulties are uncommon until the late phase of disease.2,4 Behavioural changes, including depression, anxiety, apathy, aggression, agitation, wandering, vocalization, disinhibition, and abnormal eating, are common thereafter and cause caregiver stress as well as greater use of health care service.5
Vascular Dementia
A 65-year-old man with hypertension, diabetes mellitus, and coronary artery disease developed sudden left hemiparesis and dysarthria 6 months ago. Three months later, his wife noticed that he could not name the only two grandchildren he