Transient Global Amnesia

Aka: Transient Global Amnesia

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II. Definitions

  1. Transient Global Amnesia
    1. Transient inability to form new memories (Anterograde Amnesia) in episode lasting minutes to hours

III. Epidemiology

  1. Incidence 5-10 per 100,000 per year (23 to 32 per 100,000 per year in age over 50 years)
  2. Age: Over age 50 years (typical age range 50 to 80 years)
  3. More common in women (esp. ages 40 to 60 years old)

IV. Pathophysiology

  1. Hippocampus is key in the creation of short-term memory
    1. Increased intrathoracic pressure and Jugular Venous Pressure may decrease Hippocampus perfusion
  2. Dysfunction of bilateral medial Temporal Lobes, and Hippocampus
    1. MRI Brain DWI has shown bright punctate foci in Hippocampus of TGA patients
    2. Jain (2018) Indian J Radiol Imaging 28(1): 6-9 PMID: 29692518 [PubMed]
  3. Associations with Migraine Headache, Temporal Lobe ischemia or partial complex Seizures have been postulated
  4. Venous congestion and venous reflux is also postulated as cause
    1. May explain why some TGA episodes are preceded by straining or Valsalva Maneuver
    2. Lewis (1998) Lancet 352(9125):397-9 [PubMed]

V. Risk Factors

  1. Migraine Headache (TGA Relative Risk: 6)
  2. Obstructive Sleep Apnea (TGA Relative Risk 8.4)
  3. Hypertension
  4. Hyperlipidemia

VI. Symptoms

  1. Previously well person becomes confused and amnestic
    1. Transient inability to form new memories (esp. immediate and recent)
    2. Episode lasts for minutes to hours
      1. Typically resolves within 6 hours, and always within 24 hours
    3. Patient asks orientation questions repeatedly (e.g. "Where am I?" )
    4. Maintains procedural memory (e.g. driving, eating)
    5. No associated neurologic deficits
    6. No Seizure activity or Head Trauma
  2. Associated Symptoms (variably present)
    1. Nausea
    2. Vomiting
    3. Headache
    4. Mild Dizziness
    5. Blurred Vision
  3. Spontaneous onset is typical, however is associated with triggers in some cases
    1. Valsalva Maneuver
    2. Emotional stress (e.g. learning of the death of a loved one)
    3. Significant physical exertion
    4. Sexual intercourse
    5. Water immersion
    6. High Altitude environment
    7. Extreme Temperature exposure
    8. Acute medical illness

VII. Exam

  1. Normal Level of Consciousness and orientation
  2. Impaired ability to form new memories
  3. Other intellectual tasks preserved
  4. No other neurologic deficits

VIII. Diagnosis

  1. Witnessed abrupt onset of Anterograde Amnesia (mild Retrograde Amnesia may also be present) AND
  2. Otherwise normal other cognition including normal level of conciousness, orientation and attention AND
  3. No history of Head Injury or Seizures AND
  4. Non-focal Neurologic Exam during and after the episode AND
  5. Personal identity intact (contrast with Dissociative Amnesia or Fugue State) AND
  6. Resolves within 24 hours

IX. Differential Diagnosis

  1. See Amnesia
  2. Cerebrovascular Accident, Vertebrobasilar Insufficiency or Transient Ischemic Attack
    1. Includes Posterior Circulation lesions (e.g. Basilar Artery Thrombosis)
    2. May present with Nausea, Vomiting and Acute Vestibular Syndrome
  3. Transient Epileptic Amnesia
    1. Short, rapid recurring amnestic episodes consistent with Seizure activity
    2. Complex Partial Seizures (esp. Temporal Lobe Epilepsy)
  4. Concussion
  5. Metabolic Encephalopathy
  6. Encephalitis
  7. Delirium
  8. Drug Intoxication (e.g. Alcohol Intoxication, Benzodiazepine Intoxication)
  9. Non-convulsive Status Epilepticus
  10. Atypical Migraine Headache
  11. Conversion Disorder
  12. Dissociative Amnesia (Psychogenic Amnesia)
    1. Longer duration (lasts days or longer)

X. Associated Conditions

  1. Takotsubo Cardiomyopathy
    1. Has been observed to occur concurrently

XI. Labs

  1. Fingerstick Glucose
  2. Complete Blood Count
  3. Comprehensive Metabolic Panel
  4. C-Reactive Protein (cRP)
  5. Erythrocyte Sedimentation Rate (ESR)
  6. Thyroid Stimulating Hormone
  7. Urine Toxicology
  8. Blood Alcohol Level
  9. Amonia Level

XII. Imaging

  1. MRI Brain
    1. Diffusion weight imaging demonstrate hippocampal bright punctate lesions
    2. Lesions appear in first 12-24 hours, start to fade by 72 hours and resolve by 10 days
    3. MRI also evaluates for Differential Diagnosis (e.g. CVA)

XIII. Evaluation

  1. Exclude Cerebrovascular Accident with neuroimaging
  2. Consider EEG
  3. Observe (typically in hospital until resolution)

XIV. Prognosis

  1. Complete recovery is typical by 6-24 hours
  2. Recurrs in 2 to 23% of patients
    1. Higher recurrence rate in patients with Migraine Headaches or Family History, or age <50 years at initial episode

XV. Resources

  1. Nehring, Spurling and Kumar (2020) Transient Global Amnesia, Stat Pearls (accessed 6/1/2021)

XVI. References

  1. Brown and Hachinski in Wilson et. al. (1991) Harrison's Internal Medicine, Twelfth Edition, McGraw-Hill, St. Louis, p.188-9
  2. Pensa and Swaminathan in Herbert (2021) EM:Rap 21(6): 1-2
  3. Sealy (2022) Am Fam Physician 105(1): 50-4 [PubMed]

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