Types of Dementia

While Alzheimer’s disease (AD) is the most common form of dementia, accounting for 60-80% of cases, several other types exist, each with distinct characteristics, progression patterns, and underlying pathophysiology.

Alzheimer’s Disease

Alzheimer’s disease is characterized by the accumulation of amyloid-β (Aβ) plaques outside neurons and neurofibrillary tangles of tau protein inside neurons, leading to neuronal death and brain atrophy. These pathological changes typically begin in the entorhinal cortex and hippocampus, regions critical for memory formation, before spreading to other cortical areas (Scheltens et al. 1578).

The progression of Alzheimer’s disease follows a relatively predictable pattern, beginning with memory impairment, particularly for recent events, and gradually affecting other cognitive domains, including language, visuospatial abilities, executive function, and eventually, basic activities of daily living.

Vascular Dementia

Vascular dementia, the second most common type of dementia, results from conditions that damage blood vessels in the brain, reducing blood flow and affecting brain function. These conditions include stroke, atherosclerosis, and small vessel disease. Unlike Alzheimer’s disease, which typically progresses gradually, vascular dementia may progress in a stepwise fashion, with periods of stability followed by sudden declines, often coinciding with new vascular events (Scheltens et al. 1580).

Clinical features of vascular dementia often include:

• Impaired judgment or difficulty making decisions
• Inability to plan or organize
• Decreased attention and concentration
• Difficulties with language
• Slowed thinking
• Changes in mood or behavior, including depression, apathy, and emotional lability

Lewy Body Dementia

Lewy body dementia (LBD) is characterized by the presence of Lewy bodies, abnormal deposits of the protein alpha-synuclein, in brain cells. LBD encompasses two related conditions: dementia with Lewy bodies and Parkinson’s disease dementia, which differ primarily in the timing of cognitive and motor symptoms.

Distinctive features of LBD include:

• Visual hallucinations, often vivid and detailed
• Fluctuations in cognition, attention, and alertness
• Parkinsonism (tremor, rigidity, slowness of movement, and postural instability)
• REM sleep behavior disorder (acting out dreams during sleep)
• Sensitivity to antipsychotic medications
• Autonomic dysfunction (blood pressure fluctuations, constipation, urinary difficulties)

Frontotemporal Dementia

Frontotemporal dementia (FTD) refers to a group of disorders caused by progressive nerve cell loss in the brain’s frontal or temporal lobes. These areas are associated with personality, behavior, and language. Unlike Alzheimer’s disease, which typically affects individuals over 65, FTD often begins between ages 40 and 65.

FTD is characterized by dramatic changes in behavior, personality, and/or language, with memory often relatively preserved in the early stages. Depending on which areas of the brain are affected, symptoms may include:

• Behavioral variant FTD: Changes in personality and behavior, including disinhibition, apathy, loss of empathy, compulsive behaviors, and changes in diet
• Primary progressive aphasia: Progressive language difficulties, including trouble naming objects, comprehending words, or producing speech

Mixed Dementia

Mixed dementia refers to the condition in which abnormalities characteristic of more than one type of dementia occur simultaneously in the brain. The most common form of mixed dementia is a combination of Alzheimer’s disease and vascular dementia, but other combinations are possible.

Research suggests that mixed dementia is more common than previously thought, especially in individuals over 80 years of age. In fact, many people with dementia have brain changes associated with more than one type of dementia (Alzheimer’s Association 349).