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Transient Global Amnesia
Last updated 3rd December 2020
Transient Global Amnesia
- A sudden and temporary anterograde and retrograde amnesia in the absence of any other neurological defecits
- Sometimes preceded by a precipitating event: emotional distress, pain, sexual intercourse, immersion in hot or cold water
- Pathophysiology is poorly understood – hypotheses include a vascular etiology (either arterial or venous), a migrainous phenomenon or cortical spreading depression, epilepsy and a psychogenic disorder
Epidemiology
- Affects middle-aged and elderly patients 50-70 years of age
- Patients often have vascular risk factors such as diabetes, hypertension and hyperlipidaemia
Clinical Presentation
- Anetrograde amnesia without compromise of any other neurological functions
- Accompanied with repetitive questioning – the answers to their questions are forgotten due to their inability to retain information
- Patients appear restless, nervous or confused
- Spontaneous resolution is normally within 24 hours or less
Diagnostic Criteria
- Attack must be witnessed and information available from a capable observer who was present for most of the attack
- Clear-cut anterograde amnesia during the attack
- Cognitive impairment is limited to amnesia without clouding of consciousness or loss of personal identity
- No accompanying focal neurological symptoms during the attack and no significant neurological signs afterward
- Absence of epileptic features
- Resolution of the attack within 24 hours
- Patients with recent head injury or active epilepsy are excluded
Investigations
- The diagnosis is essentially clinical but routine bloods including glucose together with CT scan to exclude acute ischaemia, head trauma and other causes are recommended
Differential Diagnosis
- Transient ischaemic attack (TIA) or stroke – isolated amnesia without other focal neurological deficits is a rare manifestation of TIA or stroke
- Epileptic amnesia – features that suggest this diagnosis include a short duration of the attack (<1 hour, usually a few to several minutes), occurrence on awakening from sleep and multiple attacks at the time of presentation
- Head injury, carbon monoxide exposure, hypoglycaemia, intoxication, drug or alcohol withdrawal, herpes simplex encephalitis and other causes of toxic metabolic encephalopathy and delirium can be confused with TGA. In such cases however, patients will usually demonstrate a more global confusion
Prognosis
- The patient will recover, they will be able to form new memories and retain information
- There does not seem to be an increased risk of ischaemic stroke although both conditions have similar risk factors
Further Information
For more information on Transient Global Amnesia, search on Dynamed Plus from EBSCO
Patient Information Leaflet on Transient Global Amnesia [pdf]