What is Transient Global Amnesia (TGA)?
The classic TGA patient asks the same questions repeatedly in the absence of other signs or symptoms. They exhibit anterograde memory loss. For instance, a patient might repeatedly ask "Have we met before" despite several introductions. Other common concurrent symptoms seen with TGA are headache, nausea, and vomiting.
Do a full neurological exam (Cranial Nerves, Sensory-Motor, Cerebellum, Reflexes). Memory function forms a crucial part of the examination as patients with TGA experience explicit memory loss i.e only the loss of memory pertaining to new facts and events (mainly stored by the hippocampus). By contrast, implicit memories (stored in the cerebellum and the basal ganglia) should not be compromised. For example, a TGA patient retains the ability to operate a car or the ability to open a door with a key. Patients also retain all other cognitive functions.
- Witnessed at onset and during attack
- Must have anterograde amnesia
- No focal neurological symptoms or signs during or after
- No epileptic features
- No clouding of consciousness, no loss of personal identity, and no cognitive impairment other than amnesia
- No head injury in the past 72 hours
- No seizures in the last 2 years, and not on medication for epilepsy
- Must resolve in 24 hours
Differentials for TGA
- Seizure/transient epileptic amnesia (lasts < 1 hour)
- Stroke (rarely presents as isolated amnesia)
- Atypical migraine
- Head injury/occult trauma/concussion syndrome (Manage as Head Injury)
- Medication and recreational drug side effect
- Herpetic encephalitis (fails to resolve in <24hrs)
- Early neurosyphilis
- HIV dementia
- Alcohol psychosis
- Alcohol blackout
What are the risk factors for TGA?
- Past history of TGA
- Advanced Age
- Migraneous Headaches
The yield of extensive diagnostic testing in search of occult etiologies is low if history is not concerning and examination is normal. However, certain high-risk patients require extensive workup. Imaging is warranted only if examination is concerning and when the duration of symptoms approaching 24 hours without resolution of symptoms. MRI is preferred over CT whenever possible to rule out an unusual neurological syndromes. If there is any suspicion of an acute ischemic stroke, immediate computed tomography (CT) should be obtained. EEG can be done to rule in seizures.
- Absence of witness at onset
- Patients aged < 50 years warrant special consideration, as TGA is rare in young individuals
- High risk - Immunocompromised, Age<50, drugs/alcohol use, Abnormal Vital Signs
- Administer Thiamine if there is h/o chronic alcoholism
- Hold medications that may explain amnestic symptoms (BZDs)
- Admit in ED Observation unit or as an in-patient for 1-2 days and watch until resolution of symptoms
- Mainstay of Rx is serial neuro examinations until the patient returns to baseline
- Neurology Consultation
- TGA is characterised by the acute onset of amnesia that can last up to 24 hours in the absence of other neurologic deficits. Symptoms resolve gradually and spontaneously within 24 hours without the need for medical intervention.
- The definitive diagnosis of TGA cannot be made until symptoms have resolved.
- For a classic case, do minimum tests but pay special attention to high-risk individuals as well as any patient with abnormal vital signs or unusual symptoms.
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