Introduction 

Have you or anyone you know ever woken up one day and experienced a sudden, unexplained memory loss? In movies, this unsettling experience is often portrayed in a condensed and dramatic version when compared to the reality of people with amnesia. This is because amnesia is more than just forgetfulness; it can alter an individual’s sense of identity and affect their ability to carry out daily activities. 

Transient global amnesia (TGA) is a condition characterised by a sudden and temporary loss of memory before, during, and after the event that led to amnesia. Furthermore, a history of migraine headaches is one of the risk factors for developing transient global amnesia. Thus, this article elucidates the connection between TGA and migraine headaches. 

Understanding transient global amnesia 

Transient global amnesia (TGA) is characterised by the inability to encode new memories (i.e., anterograde amnesia) and sometimes with a retrograde component, which could last up to 24 hours or more.¹ Repetitive questioning often accompanies this condition without further focal neurological involvement and occurs commonly in patients between the ages of 50 and 70 years. TGA is not associated with focal neurological deficits, seizures, or loss of consciousness. The symptoms include vomiting, headache, blurry vision, dizziness, and nausea.² Patients with TGA are typically not aware that they have this problem. This is why a medical professional must observe and diagnose this condition and advise on strategies to mitigate the symptoms.¹ Thus, the diagnosis relies on detailed clinical history, cognitive evaluation, and thorough physical examination.

The annual incidence of TGA has been studied to be 3.4 to 10.4 per 100,000 people.⁴ If the incidence is narrowed down to the population older than 50 years of age, the incidence rises to 23.5 per 100,000 per year.⁴ TGA is more common in individuals with migraine and more frequent in patients with a history of ischaemic heart disease and hyperlipidaemia.⁵ A TGA episode is often precipitated by a recent stressful physical or psychological event, ranging from 52% to 89% in most cases.⁵ Women are affected by TGA more often than men, and the highest incidence occurs during the seventh decade of life when risk factors and accompanying diseases are most common.⁷

Triggers of transient global amnesia 

TGA can be triggered by the following; 

• Physical exertion
• Pain (acute) 
• Sexual intercourse ⁶ 
• Emotional or psychological stress 
• Valsalva manoeuvre (straining during cough and lifting)
• Ischaemic heart disease
• History of migraine and cardiovascular issues 
• Exposure to extreme temperatures (either hot or cold)
• Slight head trauma ⁶

TGA is considered a diagnosis of exclusion. This is because it can occur among people who are typically healthy and do not have any comorbidities, risk factors, or even triggering factors.⁶ However, TGA is related to vascular risk factors, migraine, and epilepsy.

What are migraine headaches? 

Migraines are severe, unilateral headaches (i.e., on one side of the head), which can increase in intensity with physical activity or in the presence of triggers.⁸ Apart from the pulsating-throbbing headache associated with migraine, this condition can also cause a lack of appetite (most of the time), nausea (80%), and sensitivity to light (60%) and sound (50%).⁸    

When the headaches are one-sided, they may change sides during an attack. However, the severity of the attacks may vary markedly depending on the duration of exposure to triggering factors. According to the International Headache Society (IHS), the duration of attacks is between 4 and 72 hours. In children, the attacks are shorter and can manifest without headache, except for severe nausea, vomiting, and dizziness.⁸ 

Types of migraine 

According to the National Institute of Neurological Disorders and Stroke (NINDS), there are different types of migraine, and they are not limited to headaches. These include: 

• Migraine with aura: This type comes with a warning sign (i.e., an aura) that a migraine is about to happen. The aura includes visual changes, speech impediment, ear ringing, temporal paralysis on one side of the body, etc
• Migraine without aura: This does not come with a warning sign but can be severe. The headache associated with this type of migraine elicits throbbing pain, which can get worse when you move around. It is characterised by attacks that can last between 4 and 72 hours and is the most common type of migraine

A migraine can affect anyone, regardless of age, from children to adults. However, women are more likely than men to experience a migraine, especially a menstrual migraine. Other risk factors that can increase the risk of developing a migraine include a family history of migraines, underlying health conditions such as sleep issues, depression and anxiety, use of tobacco products, etc.  

The connection between TGA and migraine headache

The connection between TGA and migraine headaches stems from similar pathophysiological mechanisms of both conditions. TGA pathogenesis is focused on 3 distinct mechanisms: vascular dysfunction, epileptic activity, and migraine-related processes.¹ The short-term formation of memory is centred on the hippocampus (a brain structure central to memory formation, which appears to be a common target), and any injury to this location causes TGA. Similarly, cortical spreading depression, which leads to the activation of the trigeminal nerve in migraines, can lead to the damage of the pyramidal neurones of the hippocampus called the CA1 neurones, which are critical for memory encoding.⁹ Additionally, the Valsalva manoeuvre, which is one of the triggers of TGA, can cause a transient elevation of intrathoracic pressure. Consequently, this causes abnormal venous drainage from the temporal lobes.¹⁰ 

Therefore, the hippocampal migraine vascular changes, which can be precipitated by impaired venous drainage of the hippocampus, increase the risk of TGA accompanied by migraine headaches. This is why migraine has been identified as most prevalent in patients with TGA. Whereas hypertension, diabetes mellitus, previous ischaemic stroke, and atrial fibrillation were found to have a lower prevalence in individuals with TGA.¹¹

Management of TGA 

TGA is generally benign, with no long-term neurological consequences. The recurrence rate is low, with most individuals experiencing only one episode. When recurrences occur, they tend to happen within a few years of the first incident and are often linked to a personal or family history of migraines. Additionally, most people with recurrent TGA had 3 or fewer recurrences in 3 to 4 years.¹⁴ In comparison, individuals with recurrent episodes of TGA were similar in age, sex, length of anterograde amnesia, identifiable triggers, and electrodiagnostic findings.¹⁴

e Also, it does not increase the risk of developing other neurologic disorders, such as stroke, dementia, or epilepsy.¹⁴ Thus, the most essential part of management after diagnosis is being aware of and fulfilling the psychological needs of the patient and his or her relatives.¹³

Diagnosis of TGA 

To diagnose TGA, the following criteria should be present in the patient, as created by Hodge and Warlow in 1990.¹² 

• TGA must be witnessed by a capable observer who will also provide the required information
• Anterograde amnesia must occur during the episode of TGA 
• There should be cognitive impairment, which is limited to amnesia without other neurological deficits 
• The episode must resolve within 24 hours
• Loss of personal identity and clouding of consciousness should not occur
• There shouldn’t be a recent head injury or epileptic attack in the patient 
• No significant neurologic signs should be observed afterwards 

Summary 

• Transient global amnesia is a condition characterised by profound anterograde amnesia that can last up to 24 hours, while other neurologic functions remain intact 
• The inability to form new memories during TGA can make a patient ask certain questions repetitively, but the identity is not compromised 
• TGA can be triggered by a variety of factors, such as the Valsalva manoeuvre and sexual intercourse, but the most significant risk factor is a history of migraines
• A migraine is a severe, throbbing headache that could be accompanied by a warning sign (called an aura) or the absence of a warning sign (without an aura)
• The connection between TGA and migraine headache is due to a shared pathophysiology of both conditions
• The hippocampus, which is part of your brain’s limbic system, holds short-term memories and transfers them to long-term storage in the brain. 
• Cortical spreading depression, which induces vascular changes in the hippocampus, is the common denominator in TGA and migraine headaches
• Management of TGA involves identifying the psychological needs of the patients and family members and improving the general quality of life 
• The diagnostic criteria should be fulfilled to eliminate differential diagnoses of TGA, such as transient epileptic amnesia, which shares similar symptoms

FAQs 

How long does it take to recover from TGA?

Transient Global Amnesia (TGA) typically resolves on its own within 24 hours. Additionally, most episodes might last a few hours, and memory function can return to normal afterwards

Can TGA lead to complications? 

Transient global amnesia has no direct complications. It's not a risk factor for stroke or epilepsy. It's possible to have a second episode of transient global amnesia, especially when frequently exposed to the risk factors, but it's extremely rare to have more than two. Although TGA can cause anxiety and emotional distress, there are no severe long-term complications of this condition. 

Can TGA be prevented?

As TGA has several triggers, it is almost impossible to prevent or avoid this condition. However, some of the modifiable triggers, such as physical exertion and emotional or psychological stress, can be adjusted through lifestyle changes in order to reduce the risk of the onset of TGA.  

Can drugs cause TGA? 

A distinct benign form of TGA occurs following excessive alcohol consumption, large sedative doses of barbiturates, use of several illicit drugs, or sometimes relatively small doses of benzodiazepines. However, in some cases, TGA can occur in healthy people.