Transient Global Amnesia

Transient Global Amnesia is a topic covered in the 5-Minute Emergency Consult.

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  • Transient global amnesia (TGA) has the following features:
    • Episode of amnesia with abrupt onset
    • No focal neurologic signs or symptoms
    • Temporary, severe, anterograde amnesia:
      • Acute inability to form new memories
      • Permanent memory gap after the episode
    • Temporary short-range retrograde amnesia:
      • More recent memories at more risk
      • Previously encoded memories unavailable only temporarily
    • Gradually improves until only remaining memory deficit is the gap induced by the anterograde amnesia
  • Incidence between 3 and 8 per 100,000 people:
    • 75% occur in people of 50–70 yr old
    • TGA rare <40 yr
  • Most attacks last between 1 and 8 hr (range 15 min–7 days)


  • Multimodal MRI, SPECT, and PET have shown some abnormalities of regional blood flow in selectively vulnerable hippocampal structures
  • The exact etiology of TGA is unknown; speculation is controversial
  • Speculated causes:
    • Vasoconstriction due to hyperventilation:
      • Psychogenic hyperventilation in setting of age-related cerebrovascular autoregulatory dysfunction
    • Hippocampal venous congestion with Valsalva:
      • Ultrasonography has suggested internal jugular vein incompetence
    • Migraine (in younger patients)
  • No correlation between TGA and thromboembolic cerebrovascular disease has been found

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