Transient global amnesia (TGA) is characterized by the sudden onset of transient, anterograde amnesia without further focal neurologic deficits.^1–6 Mental status is overall normal but may include mild confusion.^1,2 Research suggests that the diagnosis is missed 90% of the time at initial presentation, often resulting in extensive and perhaps unnecessary evaluations.³

Epidemiology

The incidence of TGA is three to eight cases per 100,000 person years but increases to 23.8 cases per 100,000 in patients older than 50 years.^2,4–6 A TGA episode is often preceded by a recent stressful physical or psychological event, with reports in the literature ranging from 52% to 89%.^4–7 The most frequently cited precipitating events include acute illness, medical procedures, significant physical exertion, sexual intercourse, high-altitude environment, extreme temperatures, and Valsalva maneuver. ^5–7 Triggering emotional events can be positive or negative; TGA has been associated with birth announcements, news of suicide, and in patients learning of worsening health troubles, family concerns, financial pressures, and higher-stress urban living situations.^2,6–8

A history of migraine headache is the only diagnosis definitively associated with TGA, with a relative risk of 5.98.^9,10 This is most prevalent among women 40 to 60 years of age.^9,10 Other recent data suggest a higher rate of TGA in patients with hypertension and hyperlipidemia.¹¹ Case reports of takotsubo cardiomyopathy happening concurrently with TGA have occurred, with an odds ratio of 2.3 in a cross-sectional study of U.S. hospitalizations.¹² There have been additional reports of troponin I elevations or other concomitant cardiac events in the setting of TGA.¹³ Reports of TGA associated with severe COVID-19 have recently appeared, suggesting that the hypercoagulable state of COVID-19 may precipitate thrombotic strokes in the hippocampus.¹⁴ One case-control study demonstrated a relative risk of 8.4 for TGA associated with obstructive sleep apnea.¹⁵

Presentation

Patients may have nausea, vomiting, headache, mild dizziness, or subjective visual blurring.^1,2,4 Patients with TGA report feeling disoriented to time and believe that something is wrong with them.^1,2 This disorientation and sensation occur because of the patient's inability to encode new information with their episodic (short-term) memory. During the TGA episode, patients commonly ask repetitive questions such as “Where am I?” or “How did I get here?” Due to maintained procedural memory, learned functions such as eating, language, and driving are not impaired. TGA may last less than an hour, usually resolves within six hours, and always resolves within 24 hours.^2,16 The diagnostic criteria require that the episode be witnessed by reliable people present for most of the episode, with no reported seizure activity or recent head trauma in the patient as well as all other criteria in Table 1.¹