• Clinical science

Transient global amnesia

Abstract

Transient global amnesia (TGA) is a neurological disorder resulting in acute, transient memory loss. The etiology of this form of amnesia remains unclear, but certain triggers have been identified (e.g., strenuous physical exercise, psychological stress). Affected patients experience sudden memory loss and an impaired ability to retain any new information. Additionally, they may be disoriented to time and place, but retain full knowledge of self-identity. Transient global amnesia resolves after a maximum of 24 hours, after which time the patient spontaneously returns to their normal state of consciousness. The diagnosis is established based on the history of the episode (onset, duration, nature of amnesia). However, an EEG or contrast CT may be performed to rule out transient amnesia caused by other conditions. Transient global amnesia is predominantly associated with a good prognosis and does not indicate an underlying or impending cerebroischemic condition.

Epidemiology

  • Peak incidence: 50–70 years (patients are rarely < 40 years)

References:[1][2][3]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

  • Idiopathic
  • Precipitating factors
    • Vigorous physical exercise or exhaustion due to overwork
    • Working bent over (e.g., gardening)
    • Psychological stress
    • Sudden immersion in cold or hot water

References:[1][3][4][5][6]

Clinical features

  • Abrupt onset
  • Episodes last between 1–24 h, but never > 24 h (mean duration 6–8 h)
  • Nature of amnesia: anterograde or partial retrograde
  • The patient may appear anxious and distraught, with desperate attempts to orientate themselves.
  • The attack resolves over hours, with older memories returning first, followed by a gradually increasing capacity to retain new information.

References:[4]

Diagnostics

  • If the diagnosis is clear, further diagnostic procedures are not necessary.
  • If the diagnosis is uncertain:
    • MRI: evidence of typical focal, hyperintense lesions in the hippocampus
    • EEG: exclude differential diagnoses (e.g., epileptic amnesic attacks)

References:[1][4][7]

Treatment

  • Outpatient management is possible under the supervision of a caregiver.
  • Monitoring for at least 24 h is advisable if an alternative diagnosis is suspected.
  • No medical therapy

Prognosis

  • Resolves spontaneously within 24 h
  • Approximately 3–20% of patients may experience a further episode.

References:[4][8]