Transient global amnesia

Transient global amnesia (TGA) is a temporary and isolated disorder of memory. The patient is usually over 50 years old and an attack may last several hours.

Patients with this condition are often described - wrongly - as being confused.

The patient with TGA:

is neurologically intact except for absent memory

• asks pertinent questions repeatedly
• is unable to recall the episode once they have recovered
• presents classically with an abrupt onset of severe anterograde amnesia
• does not have any focal neurological symptoms
• patient remain alert, attentive, and cognition is not impaired
• are disoriented to time and place
• attacks usually last for 1-8 h but should be less than 24 h (1)

Epidemiological data put the annual incidence of TGA between 3.4 and 10.4/100,000 (2)

• most commonly presents in the seventh decade of life. Across studies, the mean age of an episode ranges from 61 to 67.3 years
• studies show a slight female predominance
• study evidence showed a recurrence rate of 6.3% in a 10 year period

Precipitating factors include sexual intercourse and heavy physical exercise, particularly swimming in cold water.

• possible that it may result from different mechanisms such as venous congestion with valsalva-like activities before symptom onset, arterial thromboembolic ischaemia and vasoconstriction due to hyperventilation (1)
  
• close precipitating events for TGA are considered emotional stress (i.e., triggered by gastric endoscopy, birth/death announcement, and difficult/exhausting workday), physical effort (i.e., gardening, house work, and sawing wood), physical exertion (including sexual activity), and water contact/temperature change (i.e., hot bath/shower and cold swim) (3)
  
• remote precipitating events, with onset reported weeks prior to TGA, are considered anxiety triggered by conflict at home or work, health problems, and financial stressors (3)
  
• diagnosis may be made safely in the presence of a characteristic collateral history

There is a correlation between TGA and migraine. There is no excess of cerebrovascular disease in patients with TGA

• a population-based study concluded that an episode of TGA does not increase the risk of subsequent cerebrovascular events, seizures, or cognitive impairment (4)

Diagnostic Criteria (5)

The diagnosis of transient global amnesia is primarily clinical, based on a detailed history and a thorough neurological examination during the acute stage. Advanced neuroimaging, cerebrospinal fluid analysis, and EEG are unnecessary unless the clinical diagnosis is uncertain.

• the attack onset should have been witnessed.
• dysfunction during the attack should have been limited to repetitive queries and amnesia.
• there should have been no other major neurologic signs or symptoms.
• the memory loss should have been transient, usually lasting hours or up to one day

There is no treatment

• no specific treatment is indicated for a typical episode

Reference:

1. Owen D et al. Classical diseases revisited: transient global amnesia. Postgrad Med J. 2007 Apr; 83(978): 236-239.
2. Spiegel DR et al. Transient global amnesia: current perspectives.Neuropsychiatr Dis Treat. 2017; 13: 2691-2703.
3. Portaro S et al. Risk factors of transient global amnesia - Three case reports. Medicine (Baltimore) 2018 Oct; 97(41): e12723.
4. Arena JE et al. Long-Term Outcome in Patients With Transient Global Amnesia: A Population-Based Study.Mayo Clin Proc. 2017 Mar; 92(3): 399-405.
5. Caplan L. Transient global amnesia. What's in a name? J Neurol Sci. 2022 Oct 15:441:120348.