Transient Global Amnesia: Clinical Features and Diagnostic Criteria
Transient global amnesia (TGA) is characterized by sudden-onset profound anterograde amnesia with repetitive questioning, variable retrograde amnesia, and complete resolution within 24 hours, without other neurological deficits or loss of consciousness. 1, 2
Core Clinical Symptoms
The hallmark presentation includes:
- Anterograde amnesia: Inability to form new memories during the episode, representing the most prominent feature 3, 4, 5
- Repetitive questioning: Patients repeatedly ask the same questions reflecting disorientation in time and place 3, 6
- Variable retrograde amnesia: Some inability to recall general or personal information from before the episode, though this may improve over time 3, 5
- Preserved immediate recall and remote memories: Other cognitive functions remain intact during the episode 4, 6
- Duration: Episodes last up to 24 hours by definition, with complete resolution except for amnesia of the event itself 1, 4, 6
Associated Factors and Precipitants
Physical exertion and Valsalva-like maneuvers are the most commonly identified precipitating events 4, 6. These include:
- Strenuous physical activity 4
- Sexual intercourse 6
- Sudden immersion in cold or hot water 6
- Emotional stress 5
- Medical procedures 5
Critical Diagnostic Criteria
The diagnosis requires witnessed observation of the memory loss episode and mandates the following features 1, 4:
- Absence of neurological signs or deficits beyond the memory impairment 1, 4
- No loss of consciousness at any point during the episode 4, 7
- No features of epilepsy (no seizure activity) 4
- No recent head trauma in the preceding period 1, 4
- Complete resolution within 24 hours 1, 4
What TGA Is NOT
TGA does not present with:
- Focal neurological symptoms (weakness, sensory loss, visual field defects) 2
- Altered level of consciousness or confusion beyond the memory deficit 7
- Seizure activity or postictal states 4
- Persistent cognitive deficits after resolution 6
Age and Demographics
TGA typically affects middle-aged to older adults, with most cases occurring in patients aged 50-70 years 5, 6. The condition shows no clear gender predominance 6.
Important Clinical Pitfall
Retrograde amnesia may be underrecognized, particularly in older individuals, as it can be more frequent than previously thought 8. However, unlike conditions causing global confusion, patients with TGA maintain awareness of their identity and can perform complex tasks despite their inability to form new memories 3, 7.
Recurrence Risk
The relapse rate is low, with most patients experiencing only a single episode in their lifetime 6. When episodes are brief and recurrent, alternative diagnoses such as epilepsy should be strongly considered 2, 6.