Introduction

Transient global amnesia (TGA) is a short-term neurological condition which lasts less than 24 hours, during which people cannot form new memories; this phenomenon is known as anterograde amnesia. There is also retrograde amnesia, where people are unable to remember recent events, which is also present in TGA.¹ 

There are many symptoms that are indicative of this condition, such as ataxia, where muscle control is compromised. The limbs of those affected appear to be weaker, with sensory experiences being altered and disturbed. These symptoms are used to differentiate TGA from other conditions that have a similar presentation, such as epileptic amnesia and transient ischemic attacks, where people have stroke-like symptoms.² 

The recurrence rates for this condition vary greatly between studies, and the long-term outcomes of TGA are still being investigated.³ This article will explore the prognosis (development) of this condition by assessing its causes, as well as the outcomes for those affected, in conjunction with recurrence rates. Management strategies for how to best alleviate symptoms will also be covered.

Causes and risk factors of TGA

TGA may be triggered by a variety of causes, such as when you are very physically active and overly exert yourself. Valsalva-like manoeuvres, which are used medically to slow a fast heart rate, have benefits, but the increased strain and pressure they create in the body are thought to potentially trigger TGA episodes in susceptible individuals.⁴ People who experience migraines are also more likely to be at risk for this condition, as well as those with high stress levels, as this is linked to the pathophysiology of TGA.⁵ Demographic factors may also strongly influence the prevalence of this condition, with most people having TGA between the ages of 40 and 80. However, it is largely accepted that biological sex does not significantly affect its prevalence.⁶ 

The pathophysiology of TGA is still not clear. One proposed mechanism involves venous congestion, where the veins have very high blood pressure, causing blood flow to regions of the brain to be compromised. This reduction in blood flow is thought to partially cause TGA.² Other theories include migraines decreasing brain activity and function due to ion imbalances in the cerebral cortex. Previous emotional trauma is also thought to affect brain regions, such as the hippocampus (part of the brain responsible for memory), thus leading to TGA presentation.⁷

Immediate and short-term prognosis

TGA leads to a few different outcomes in the short term. The aforementioned anterograde amnesia can be present for up to 24 hours; however, this is typically resolved within 6 hours, meaning that patients can form new memories after this time period. Some people may experience recurrent episodes of TGA that last for up to 72 hours.⁸ Typically, retrograde amnesia is resolved before anterograde amnesia due to areas of the brain, such as the hippocampus, being amongst the last parts to recover from TGA.⁹ It is important to note that cognitive impairment and memory issues vary between individuals, and symptoms may last longer than a day in some instances.¹⁰ 

Immediately after an episode, people may exhibit behavioural changes such as neglecting a routine, alongside being confused and disoriented. The implication is that those affected by TGA are largely unable to work whilst recovering from a TGA episode, and should therefore be allowed work leave.¹¹

Long-term outcomes of TGA

Some studies have concluded that TGA does not lead to an increased chance of long-term cognitive impairment. The time taken to decline cognitively with age is the same in those with and without TGA. It has also been found that the chance of seizures is not significantly affected by TGA occurrences, and strokes are not more likely to occur in those individuals with TGA.^3,12 It has been documented, however, that many people are anxious about a possible memory impairment and tend to worry about memory issues in the long-term, even though this may not be the case.¹³ Overall mortality and vascular issues are generally unaffected by TGA, though people with TGA are more likely to be susceptible to epilepsy in the future. More studies need to be done on this condition to establish the mechanism and reasoning behind this.¹⁴

Recurrence rates of TGA

For some people, TGA is a recurrent illness, which means that some are affected to a greater extent by this condition and its symptoms than others. For instance, the risk of recurrence is higher in those who experience migraines.¹⁵ Alongside migraines, other risk factors make the rate of recurrence more likely, including mental health issues such as depression, dementia, and previous head injuries. It is important to note that the link between head injuries and dementia due to recurrent episodes is not as strong as that between migraines and TGA recurrence.¹⁶ Recurrent episodes can be more severe and lead to worse consequences, such as a permanently impaired memory and other neuropsychological issues, such as dyspraxia. Amnesic strokes, in which memory loss occurs due to an issue with the vascular system, are also possible and more likely in recurrent TGA than when a person has a TGA episode for the first time.¹⁷

Management and prevention strategies

There are ways to manage TGA and lower the likelihood of susceptible people being affected by this condition. As mentioned before, stress is a primary cause of TGA and leads to memories not being formed correctly. This means that by reducing stress through avoiding certain triggers and implementing practices such as meditation, the likelihood of suffering from TGA is reduced.¹⁸ Managing neurological and medical conditions which lead to TGA or are strongly associated with this condition, such as migraines, is also crucial in managing TGA.¹⁹ Monitoring those who have experienced an episode by using techniques such as magnetic resonance imaging (MRI) is useful in finding out whether they are likely to suffer another episode. This will also allow for prevention and treatment strategies to be implemented.²⁰ Finally, increasing awareness of this condition and educating people on prevention strategies will greatly improve future outcomes and quality of life.²¹

Summary

In summary, TGA is typically a benign condition that lasts for 24 hours or less in the majority of cases, being more common in patients with mental health issues and migraines. 

Many people affected by this condition are anxious about long-term issues, which may include dementia and epilepsy. However, there are strategies to manage TGA. Reducing stress, as well as medical monitoring, lowers the risk. There is also an increasing amount of research regarding the long-term prognosis of TGA and the exact pathophysiology of this condition. With increased awareness, education, and management strategies becoming readily available, the prevalence of this condition may decrease in the near future, and outcomes for those with this condition may improve over time.