Dementia

Basics

Description

  • Chronic cognitive decline severe enough to interfere with activities of daily living
  • Heterogeneous syndrome defined by progressive deterioration of one or more cognitive domains (language, memory, complex attention, perceptual-motor, social cognition)
  • A chronic and progressive form of organic brain syndrome
  • Most common cause is Alzheimer dementia (60–80% of cases), followed by vascular dementia, mixed dementia, and dementia with Lewy bodies
  • Affects between 5–16% of individuals between age 65 and 85 and between 30% and 40% in people >85 yr old
  • Incidence of dementia has decreased in past few decades, although there has been a rise in absolute number of patients with dementia worldwide
  • Characterized by gradual decline in cognitive functioning:
    • Typically evolves over years
    • Rapid decline indicative of other causes, or rare rapid onset causes of dementia (prion diseases, progressive supranuclear palsy)
  • Variable hereditability:
    • Increased risk of Alzheimer disease in 1st-degree relatives of patients with Alzheimer
    • Apolipoprotein ε4 is the only well-established mutation with late-onset Alzheimer

Etiology

  • Neurodegenerative changes in the brain, characterized by neuronal damage and loss, abnormal protein accumulation, and disruption of synaptic function
  • Over 50 different causes
  • Primary dementia:
    • Cortical (Alzheimer disease, frontotemporal dementia)
    • Subcortical (Huntington disease, Parkinson disease, progressive supranuclear palsy)
  • Secondary dementia:
    • Cerebrovascular disease (multi-infarct dementia)
    • Toxic, metabolic, nutritional derangements
    • Prion disorders (Creutzfeldt–Jakob or bovine spongiform encephalopathy and variants)
    • Infectious agents (HIV, syphilis, encephalitis)
    • Vasculitis (systemic lupus erythematosus, thrombotic thrombocytopenic purpura)
    • Traumatic (chronic subdural hematomas, pugilistic dementia, chronic traumatic encephalopathy)
    • Structural (normal pressure hydrocephalus, brain masses)
    • Binswanger disease
  • Reversible causes (15%) include normal pressure hydrocephalus, adverse effects of medications, intracranial masses, and alcohol use disorder
  • Pseudodementia:
    • Depression in elderly can present with dementia-like symptoms
    • Common in mildly demented patients, look for pin-point event with short duration of symptoms
    • Typically seen in patients with preexisting psychiatric disorders

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