Transient Global Amnesia (TGA)
Transient global amnesia is a benign, temporary neurological syndrome characterized by sudden onset of anterograde amnesia with preserved immediate recall and remote memories, typically lasting less than 24 hours, with no long-term neurological consequences. 1
Definition and Clinical Features
Transient global amnesia presents with the following key characteristics:
- Sudden onset of profound anterograde amnesia (inability to form new memories)
- Variable retrograde amnesia (difficulty recalling past events)
- Preserved immediate recall and remote memories
- Repetitive questioning due to inability to retain new information for more than 30-180 seconds 2
- Preservation of other cognitive functions and personal identity
- No accompanying neurological deficits 1, 3
- Complete resolution within 24 hours 1
Epidemiology
- Most commonly affects individuals over 50 years of age 2
- Recent epidemiological data suggests an annual incidence of approximately 15 cases per 100,000 people 2
- Recurrence rate estimated between 2.9% to 23.8% over a lifetime 1
Diagnostic Criteria
According to Hodge and Warlow criteria 3, TGA diagnosis requires:
- Witnessed episode of memory loss involving anterograde amnesia
- No neurological signs or deficits
- No features of epilepsy or active epilepsy
- No recent head injury
- Resolution within 24 hours
Precipitating Factors
TGA episodes are often preceded by:
- Physical exertion, especially with Valsalva-like maneuvers 2, 3
- Emotional stress
- Temperature extremes (hot/cold water exposure)
- Sexual activity
- Pain
Diagnostic Workup
- Clinical diagnosis is primarily based on characteristic presentation and exclusion of other causes 1
- MRI brain: May show punctate lesions in the CA1 field of the hippocampus in 50-90% of cases when performed 24-72 hours after symptom onset 4, 2
- Basic laboratory tests should be performed to exclude metabolic causes:
- Complete blood count
- Electrolytes
- Glucose
- Thyroid function
- Vitamin B12 levels 1
Differential Diagnosis
TGA must be distinguished from other causes of acute amnesia:
- Transient ischemic attack (TIA)
- Stroke
- Seizures, particularly temporal lobe epilepsy
- Psychogenic amnesia
- Acute intoxication
- Head trauma
- Wernicke's encephalopathy
Pathophysiology
The exact mechanism remains unclear, with several theories proposed:
- Vascular mechanisms (venous congestion in temporal lobes)
- Migraine-related phenomena
- Epilepsy-like activity
- Psychological factors
- Hippocampal network dysfunction 2
Management and Prognosis
- No specific treatment is required during an episode 1
- Reassurance to patients and family members about the benign nature of the condition
- No increased risk of subsequent stroke or TIA 1
- No need for long-term medication 1
- No increased mortality associated with TGA 3
Key Points for Clinical Practice
- TGA is a clinical diagnosis based on characteristic presentation
- The condition is self-limiting and benign
- Patients and families should be reassured about the excellent prognosis
- No specific preventive measures or treatments are required
- Recurrences may occur but are generally infrequent
TGA represents a dramatic but ultimately benign neurological phenomenon that resolves completely, requiring primarily recognition and reassurance rather than specific interventions.