Internal Medicine Board Review: Dementia

Dementia is an important topic to understand for the USMLE Step 3, ABIM, and on other medical exams where internal medicine is a major focus. The following is an excerpt out of Cracking the USMLE Step 3.

• Dementia
  • Global cognitive decline in functioning
    • Not limited to certain area of the brain
  • Consciousness does not wax and wane like in delirium
  • EEG usually normal
  • Differential diagnosis of dementia:
    • Alzheimer’s Dementia (AD)
    • Vascular Dementia
    • Pick’s Disease
    • Pseudodementia
      • Depression in the elderly that presents as dementia
      • Remember to inquire about guilt, concentration, anhedonia, sleep, appetite, and mood
      • Critical to assess suicidality given increased risk in elderly
    • Chronic subdural hematoma
      • Rule out with CT
    • Dementia pugilistica
      • Seen in boxers and football players
      • Caused by repeated trauma to the head
    • Parkinson’s Disease (PD)
      • Dementia occurs late in disease course
    • Lewy Body Dementia (LBD)
      • Similar to PD, but dementia occurs early in disease course
    • Multiple Sclerosis (MS)
    • Normal aging
      • No cognitive deficits
      • No limitation in everyday activities
      • May have some memory loss
    • Hypothyroidism
      • Check TSH, total/free T4 and T3
    • Vitamin B12 deficiency
      • Check serum Vitamin B12 levels
      • More sensitive to check homocysteine and methylmalonic acid levels, both of which are increased in Vitamin B12 deficiency
    • Folate deficiency
      • Check serum folate levels
    • Niacin (B3) deficiency
      • Causes pellagra:
        • Dementia
        • Diarrhea
        • Dermatitis
      • Normal Pressure Hydrocephalus (NPH)
      • Neurosyphilis
        • Check RPR and VDRL in CSF
      • HIV
        • Usually occurs years after infection
        • Check Elisa as screening test (i.e., highly sensitive)
        • If positive, check Western blot (i.e., highly specific)

• Alzheimer’s Dementia (AD)
  • Cholinergic defect due to Damage to the Nucleus Basalis of Maynert
  • AD common in Down’s syndrome patients who reach the age of 40
  • EpoE4 allele increases the risk for AD
  • EpoE2 allele protective against AD
  • Present with memory loss
  • Ruling out other reversible causes of dementia:
    • Hypothyroidism
    • Syphilis
    • Vitamin B12 deficiency
    • Folate deficiency
    • HIV
    • Normal Aging Process
  • MMSE score below 27 is consistent with dementia
    • Below 20 consistent with severe dementia
  • MRI shows atrophy of temporal lobes (i.e., hippocampus)
    • Can progress to atrophy of all lobes
  • On autopsy, histology shows tau (i.e., intracellular, forms tangles) and β amyloid (i.e., extracellular, flame-like appearance)
  • Consider donepezil, rivastigmine, or tacrine (i.e., acetylcholinesterase inhibitors) to reduce rate of cognitive decline
  • Consider memantine (i.e., NMDA antagonist) or new AMPAkines to slow cognitive decline if refractory
  • Vitamin E: Possible therapeutic benefit
  • Poor prognosis:  Aspiration pneumonia is most common cause of death in AD

• Vascular Dementia (i.e., Binswanger Disease)
  • Consider diagnosis in a patient with a history of multiple TIAs, strokes, or other coronary artery disease risk factors or equivalents including angina pectoris, myocardial infarction, diabetes mellitus, or hypertension
  • MRI may show multiple areas of strokes within periventricular white matter
  • Treatment involves controlling risk factors and preventing further strokes