Overview

Transient global amnesia (TGA) is a sudden and temporary episode of memory loss that can be alarming for those who experience it and their loved ones. Unlike conditions such as alzheimer’s disease or stroke, TGA does not lead to permanent damage or long-term cognitive decline, nor is it linked to neurological conditions such as seizures.¹ However, the exact cause of TGA remains unclear. Researchers have identified several potential triggers, including emotional stress, physical exertion, and sudden temperature changes.² Understanding these triggers can help in recognising and possibly preventing episodes of TGA.

What is transient global amnesia?

TGA is a condition where a person suddenly experiences short-term memory loss. They may also repeatedly ask the same questions because they cannot retain new information.² Despite this, they remain aware of their identity and retain other cognitive functions, such as language and problem-solving skills. Episodes of TGA typically last less than 24 hours (normally 4-8 hours, but can be as short as 30-45 minutes), and once the episode ends, memory function gradually returns to normal without lasting effects.^3,4

TGA is rare, with an incidence of 5.2 to 10 per 100,000 each year in the general population.⁵ It mainly affects middle-aged and older adults, with an incidence of 23.5 to 32 per 100,000 in individuals over 50 years old.^5,6 TGA occurs most commonly in people between the ages of 60 and 69, with the average age range being from 61 to 67.3 years.⁶ TGA affects slightly more females than males.⁷ Although it is a temporary and benign condition, its sudden onset can be distressing. The exact cause remains unknown, but researchers have identified various factors that may contribute to its occurrence.

Potential triggers of TGA

While TGA can occur without any clear cause, studies suggest that certain activities or situations may trigger an episode. There are 50-90% of documented TGA cases that were caused by triggers which can be put into one of the following categories: 

• Emotional stress (e.g., triggered by conflict, a birth or death, a medical procedure, or a challenging day)
• Physical exertion (e.g., exercise, manual labour, housework, or gardening) 
• Sudden temperature change (hot bath or shower, or swimming in cold water)
• Acute pain
• Sexual intercourse
• Valsalva-associated manoeuvres (a breathing exercise which slows down the heart)- Accounted for 41% of cases in one study⁸
• Unspecified⁹

In general, in individuals assigned male at birth (AMAB), TGA occurred due to a physical event, whereas in those assigned female at birth (AFAB), TGA occurred due to an emotional event.⁹ Nevertheless, psychological and emotional distress account for a significant proportion of triggers of TGA (most commonly in those with a phobia).⁹ Additionally, episodes of TGA commonly take place in the morning between 10 and 11 AM and in the evening between 5 and 6 PM.¹⁰  

Physical exertion

Strenuous physical activity is a common trigger for TGA. Engaging in demanding exercises such as long-distance running, heavy weightlifting, or even sexual activity has been linked to episodes.¹¹ Scientists believe that intense exertion may cause temporary disruptions in blood flow to the brain, particularly the hippocampus, which is responsible for memory formation.⁷ However, it is important to note that TGA is not linked to heart attacks or strokes, and people experiencing an episode usually recover fully. If signs of amnesia are still present after 24 hours, however, stroke, intoxication, Wernicke–Korsakoff encephalopathy, limbic encephalitis, and psychogenic (dissociative) amnesia will need to be ruled out.¹²

Emotional stress and psychological factors

Experiencing strong emotional reactions, such as shock, anxiety, or grief has been associated with TGA. Receiving unexpected bad news, going through a stressful event, or even intense excitement can act as triggers.⁷ Stress or anxiety triggered by conflict, health issues, or financial difficulties are normally reported weeks prior to a TGA episode.⁷ Stress may affect the brain’s ability to regulate memory processes, leading to a temporary breakdown in how short-term memories are stored and retrieved.

Studies have shown that people with high levels of anxiety or those prone to emotional distress may be at a slightly higher risk of experiencing TGA. A history of depression is associated with a 4 times higher risk of TGA.¹⁵ While TGA has been linked to psychiatric disorders, its occurrence does not necessarily indicate a chronic mental health issue.⁷

Sudden temperature changes

A sudden and extreme change in temperature, such as plunging into cold water or entering a hot sauna, has been reported as a trigger for TGA. This could be due to a temporary shock response that affects blood circulation in the brain.⁷ Some cases have been observed in individuals who went for a swim in cold water or took an ice bath. Additionally, TGA has been linked to both cold and warm weather, while some researchers theorise that there is no link between environmental temperature and TGA.^4,13 The exact reason why sudden temperature changes affects memory processing is not entirely understood, but it is believed that blood vessel reactions play a role in disrupting normal brain function.¹³

Medical conditions linked to TGA  

 Although no single explanation fully accounts for TGA, researchers have proposed several theories and associated medical conditions. 

Vascular (blood flow) theory

One leading hypothesis is that TGA results from temporary disruptions in blood flow to the hippocampus, a brain region critical for memory formation. This may happen due to venous congestion (when blood flow is temporarily blocked or slowed down in the veins).⁷ Some researchers suggest that activities causing a sudden increase in pressure in the veins, such as straining during physical exertion or experiencing emotional stress, may contribute to this temporary change in flow.^13,14 Additionally, cardiovascular diseases such as ischaemic heart disease and hyperlipidaemia have been linked to TGA.¹³

Migraine theory

There is evidence that people who suffer from migraines may be twice as likely to experience TGA.¹⁵ Some scientists believe that TGA could share similar underlying mechanisms with migraines, such as temporary disruptions in brain function caused by changes in blood vessel activity.⁹ However, unlike migraines, TGA does not cause headaches or visual disturbances. 

Epilepsy theory

Some researchers have explored whether TGA might be a mild, non-recurring form of epileptic activity in the brain. However, studies have found little evidence to support this, as brain scans of individuals experiencing TGA do not show typical patterns seen in epilepsy.⁹

Psychiatric condition theory

Certain personality traits may play a role in the occurrence of TGA. Studies have found a link between TGA and depression, anxiety disorders, and phobias.⁹ 33.3% of TGA patients reported a family history of psychiatric illness.⁹ Other studies have also identified a link between TGA and psychological instability, as well as a heightened tendency toward feelings of guilt.⁹

How is TGA diagnosed?

Current diagnostic criteria for TGA have been in use since 1990.⁷ TGA is diagnosed based on clinical symptoms and by ruling out other serious conditions such as stroke, seizures, or brain injuries. Typical steps include:

• History – Signs, symptoms, and events leading up to the episode must be reported. The following are criteria used to diagnose TGA based on history:
  • TGA episode must be witnessed
• Repetitive questioning such as, “Where am I? What is happening? What is the time?” must be witnessed⁴
  • Anterograde amnesia (memory loss with inability to create new memories)
  • Amnesia must be the only cognitive impairment
  • No clouding of consciousness or loss of personal identity
  • No loss of function of one part of the body (focal neurological signs)
  • No signs of epilepsy
  • Resolves within 24 hours
  • No recent head injury⁷
• Neurological examination – Checking for ataxia (loss of bodily movements), muscle/limb weakness, and sensory issues. There are also assessments for cognitive function, reflexes, and overall neurological health
• Brain imaging tests – MRI or CT scans may be conducted to rule out stroke or other abnormalities
• Blood tests – To check for signs of infection or metabolic imbalances
• Electroencephalogram (EEG) – This test measures electrical activity in the brain to rule out epilepsy

Since TGA does not cause permanent damage, treatment is usually not required. The focus is on ensuring the person is safe, reassuring them and their family, and monitoring recovery.

What to do if someone has an episode of TGA

If someone experiences sudden memory loss and confusion:

• Remain calm – Although TGA can be distressing, it is temporary and not life-threatening
• Seek medical attention – While TGA itself is not dangerous, it is important to seek a professional to rule out more serious conditions such as stroke
• Reassure the individual – Let them know that their memory will return to normal within a few hours
• Monitor symptoms – If symptoms persist beyond 24 hours or if there are other concerning signs (such as weakness, speech problems, or loss of consciousness), further medical evaluation may be needed

Summary

Transient global amnesia is a temporary but startling condition that causes sudden memory loss. Although the exact cause remains unclear, certain triggers such as physical exertion, emotional stress, and temperature changes are believed to contribute to its onset. While TGA can be frightening, it is not linked to long-term brain damage and most individuals recover fully within a few hours. Understanding potential triggers and risk factors can help people recognise the condition and seek appropriate medical attention when needed. As research continues, scientists hope to uncover more about the mechanisms behind TGA and how to prevent it.