Introduction: A case of mistaken identity?

Transient Global Amnesia (TGA) is a condition in which someone experiences abrupt, temporary memory loss, making it difficult to form new memories or recall recent events. However, it's worth noting that the person experiencing an episode of TGA will remain alert and cognitively intact throughout.¹ On the other hand, a seizure is caused by abnormal electrical activity in the brain cells. The person experiencing a seizure has little to no awareness of their surroundings and no control over their behaviour.²  Due to the similarities in the triggers and clinical presentations of these two conditions, especially the sudden onset of memory loss,  they are often mistaken for each other. Although TGA is generally thought to be harmless, it is very important to rule out serious conditions like seizures and stroke during the diagnosis process to provide the proper medical advice.³ This article will explore the similarities, differences, and difficulties in the diagnosis of both these conditions, with the hope of educating readers and helping them understand these neurological conditions better.

What is transient global amnesia? The mystery of sudden memory loss

Before delving into the details of TGA, it is essential first to identify and understand the different types of amnesia. Amnesia is characterised by memory loss and is divided into two subtypes. Anterograde amnesia is the inability to form new memories, whilst retrograde amnesia is the inability to recall recent memories. A person with TGA may experience both anterograde and retrograde amnesia, where the former is more prevalent amongst patients.

Duration of occurrence and target population:

The word “transient” means temporary, indicating that the memory loss that occurs during a TGA episode is short-lived. A TGA episode can last for several hours to 24 hours at most in some rare cases. During recovery, the person might start to remember events and circumstances. The condition is rare and mainly affects middle-aged or older patients (aged 50 and above). A few studies have revealed that people with high cholesterol, heart conditions, and migraines are more likely to develop TGA.

Symptoms

• Apart from amnesia, people with TGA appear to be confused. They might not remember how they got to a place or why they came there
• They might be asking the same questions to the people around them repeatedly since they cannot remember the answers
• They might go blank or seem disoriented
• A few people might also experience physical symptoms like headache, nausea, and anxiety during an episode

However, people with TGA do not experience loss of consciousness or control over their bodies. They will still be able to remember their close family and friends, recognise familiar objects and remember simple directions. They will be able to perform mundane tasks like cooking or driving and will not show any cognitive symptoms, such as language loss.

Causes and Triggers

Although people with certain health conditions are more prone to developing TGA, researchers haven’t determined the exact cause of the condition. Some believe it may be caused by a blockage in the blood vessels leading to the brain, resulting in insufficient blood supply to the brain. Whilst others think that TGA could be caused by a short-term problem with the hippocampus, the part of the brain that controls memory.

Some of the most commonly reported triggers include:

• Performing strenuous physical activity
• Sexual intercourse
• Physical pain or a mild head injury
• Sudden immersion in extremely hot or cold water
• Stress

While TGA is not known to be fatal, its onset can be frightening and can cause a lot of anxiety to the patient.⁴

What are seizures?

As discussed previously, seizures are caused by abnormal electrical activity in the brain. A person experiencing a seizure has no control over their body movements, no knowledge about their surroundings and can also experience loss of consciousness. There are two types of seizures. A focal seizure occurs when an abnormal electrical impulse begins in a specific region of the brain and spreads from there. The symptoms that patients experience during a focal seizure can be diverse, depending on the area from which the abnormality originates. On the other hand, a generalised seizure occurs when all regions of the brain experience abnormal electrical activity simultaneously.⁵  

Duration of occurrence and target population

A seizure typically lasts from 30 seconds to 2 minutes and stops on its own. If it lasts for more than five minutes, the patient must be taken to a doctor immediately.

A seizure can affect people of all age groups. It can often be a symptom of some serious medical condition, like stroke, high fever, or epilepsy, with patients suffering from these conditions more likely to experience a seizure.⁶

Symptoms

The symptoms of someone having a seizure vary depending on the type. However, most people experience this common set of symptoms:⁷

• People experiencing a seizure often lose awareness of what is happening around them and lose control over their actions. While a few might urinate unintentionally during a seizure, others might start wandering, unaware of their surroundings
• People might also experience twitching, sudden stiffness or floppiness in their bodies
• They might lose consciousness or their ability to stand still
• They might experience loss of memory
• Some people may also experience other sensations, such as numbness, tingling, or fear

Causes and triggers

Brain cells use electrical impulses to communicate with each other. Seizures occur when there are changes in how these brain cells communicate. Epilepsy is a major cause of seizures, and someone suffering from epilepsy can experience seizures multiple times, regularly. Although epilepsy is the most common cause of seizures, they can also be caused by:

• A high fever (such seizures are called a febrile seizure)
• A brain infection
• Overconsumption of alcohol or use of recreational drugs
• Severe head injury that can cause internal bleeding
• Usage of medications that are used to treat mental health conditions like depression
• Usage of medication that can deplete blood sodium levels       
• Lack of sleep
• Some types of seizures are also triggered by flashing lights

Most seizures are harmless. But people with recurring seizures require a proper medical diagnosis and medications prescribed by doctors to keep their condition under control. Although seizures by themselves are harmless, we must treat a person experiencing a seizure with extreme caution and care since they have little knowledge of what is happening to them and no control over their actions.⁶

TGA vs. Seizures: Exploring the Similarities

People often confuse TGA and seizures due to the similarities in their clinical presentation. People with both conditions experience a temporary loss of memory and confusion during/after the episode. As well as having similar symptoms, these conditions also share a few triggers, like lack of sleep, recent head injury, emotional stress, and physical exertion.

People with either condition have little to no knowledge of when episodes can begin, and it is also hard for those around them to predict their onset. Additionally, both episodes resolved on their own in both conditions.

Differences and the need for accurate diagnosis

A major difference between the conditions is the duration of their episodes. A seizure lasts for a maximum of a few minutes; however, an episode of TGA can last several hours. A person experiencing an episode of TGA is mostly conscious, aware of their surroundings, and capable of performing basic tasks. However, a person experiencing seizures loses control over themself and has no awareness of their surroundings. The physical manifestations of a seizure are much more apparent and severe.

An electroencephalogram (EEG) is a test that measures the electrical activity of the brain. People experiencing TGA will have no issues with the electrical activity of the brain; however, abnormalities can be seen on EEG tests performed on patients with seizures.^4,6

Magnetic resonance imaging (MRI) is an imaging technique that uses radio waves to assess brain function. A few studies indicate the presence of lesions in the brain region associated with memory in patients with TGA. These lesions are not seen in patients experiencing seizures.⁸

Summary

Given their similarities, it is very easy to misdiagnose one condition as the other.

TGA is a rare and harmless condition compared to seizures. In most cases, it can be managed without medical intervention. Although some studies believe that it might be a type of epilepsy.⁸ Nobody knows for sure, and there is a growing need to research more about the causes to rule out the possibility of TGA being linked to serious health conditions.

Seizures do not require much medication, and although they are incurable, they can be controlled using medications prescribed by doctors. In some cases, they can even prove to be fatal if they present themselves as a symptom of conditions like stroke or brain infection.

Therefore, a thorough medical evaluation is essential to identify potential risk factors and ensure the patient's safety.