Summary
Transient global amnesia (TGA) is a neurological disorder characterized by acute, transient memory loss lasting ≤ 24 hours. The etiology of TGA is unclear, but certain triggers (e.g., physical exertion, psychological stress) have been identified. Affected individuals experience a sudden inability to retain new information (i.e., anterograde amnesia), with or without partial retrograde amnesia. Patients often present with mild agitation, anxiety, and/or disorientation but are typically alert and oriented to self. No other new neurological deficits or cognitive impairments are present. TGA is a clinical diagnosis, but diagnostic studies (e.g., MRI, laboratory studies, EEG) are often obtained to rule out other causes of amnesia. The condition is self-limited by definition, and no specific treatment is indicated. TGA recurs in a minority of patients, but the prognosis is otherwise good.
Epidemiology
- Incidence: 3–10 cases per 100,000 per year [1][2]
- Peak age: 50–80 years; rarely occurs in individuals < 50 years of age [1][2]
Epidemiological data refers to the US, unless otherwise specified.
Etiology
- Idiopathic [1][3]
- Precipitating factors (common) [1][3]
- Physical exertion (e.g., athletic activity, sexual intercourse, strenuous work)
- Psychological stress
- Medical procedures
- Severe pain
- Extreme temperatures (e.g., sudden immersion in cold water)
Clinical features
- Abrupt onset
- Anterograde amnesia with or without partial retrograde amnesia
- No focal neurological deficits or other new cognitive impairments
- Preserved alertness and orientation to self
- Patients often present with mild agitation, disorientation, and/or anxiety.
- Return to baseline within 24 hours (often within 6 hours) [1]
Rapidly recurring episodes of acute amnesia lasting < 1 hour suggest transient epileptic amnesia rather than TGA.[1]
Diagnosis
Clinical diagnosis [1][3]
-
TGA is diagnosed clinically based on the typical clinical features of TGA, including:
- Complete resolution within 24 hours
- No changes in the level of consciousness
- No recent head injury or seizures
- Diagnostic studies are not required for TGA but are commonly obtained to rule out differential diagnoses.
Consider TGA in patients with new-onset amnesia lasting ≤ 24 hours and no other neurological findings.
MRI [1]
-
Indication
- Obtain when a structural cause of transient amnesia is suspected.
- Consider within 12–24 hours of symptom onset to support the diagnosis.
- Findings: focal, hyperintense lesions in the hippocampus
Focal neurological deficits and/or seizures exclude TGA. Obtain CNS imaging if stroke or other structural lesions are suspected.
Additional diagnostics [1]
Consider other diagnostics for altered mental status (AMS) to rule out alternative causes of AMS, e.g.:
- Laboratory studies: CBC, CMP, TFTs, ethanol level, urine toxicology
- CT head: if recent head injury or hemorrhagic stroke are suspected
- EEG: if there is concern for seizure (e.g., in patients with recurrent episodes of amnesia)
Differential diagnoses
- Other conditions that may manifest with acute memory loss include: [1][2]
- Stroke or transient ischemic attack
- Transient epileptic amnesia
- Migraine
- Transient amnesia due to traumatic brain injury
- Intoxication (e.g., benzodiazepines, alcohol)
- Hypoxia
- Dissociative amnesia
- Also see “Causes of altered mental status.”
The differential diagnoses listed here are not exhaustive.
Treatment
TGA is a self-limited condition. No specific treatment is indicated once the differential diagnosis is ruled out. [1][4][5]
- Observe the patient until amnesia has fully resolved.
- Reassure patient and caregivers.