Amnesia : Causes, Symptoms, Diagnosis, Treatment, and Prevention



Amnesia refers to the loss of memories, such as facts, information and experiences. Though forgetting your identity is a common plot device in movies and television, that's not generally the case in real-life amnesia.

Instead, people with amnesia " also called amnestic syndrome " usually know who they are. But, they may have trouble learning new information and forming new memories.

Amnesia can be caused by damage to areas of the brain that are vital for memory processing. Unlike a temporary episode of memory loss (transient global amnesia), amnesia can be permanent.

There's no specific treatment for amnesia, but techniques for enhancing memory and psychological support can help people with amnesia and their families cope.

Introduction from Mayo Clinic


The brain’s mechanisms for storing information and recalling it from memory are located primarily in the temporal lobe and frontal lobe, but many areas of the brain are involved in memory. For example, the hippocampus, located deep within the brain, is involved in the formation of new memories and retrieval of stored memories. The hippocampus is part of the limbic system, which controls the experience and expression of emotions. Thus, the hippocampus helps connect memories to the emotions experienced when the memories form.

Emotions originating from the limbic system can influence the storing of memories and their retrieval. The limbic system includes part of the cerebrum and some structures deep within the brain. Areas that are responsible for alertness and awareness in the brain stem also contribute to memory.

Because memory involves many interwoven brain functions, damage almost anywhere in the brain can result in amnesia.

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What is amnesia?

Amnesia is a form of memory loss. Some people with amnesia have difficulty forming new memories. Others can’t recall facts or past experiences. People with amnesia usually retain knowledge of their own identity, as well as motor skills.

Mild memory loss is a normal part of aging. Significant memory loss, or the inability to form new memories, may indicate the presence of an amnestic disorder.

So Amnesia is a general term that describes memory loss. The loss can be temporary or permanent, but 'amnesia' usually refers to the temporary variety. Causes include head and brain injuries, certain drugs, alcohol, traumatic events, or conditions such as Alzheimer's disease. Anterograde amnesia means that the person can't learn anything new, while retrograde amnesia means the person forgets events from their past. In many mild cases, such as those caused by concussion, the person can't recall the blow to the head or their recovery time, but the rest of their memory is intact. Infantile amnesia, or the inability to remember anything at all from the first few months or years of life, is universal. It is thought that the memory processes of the brain take time to develop.



Symptoms of amnesia

The primary symptom of amnesia is memory loss or inability to form new memories. If you have amnesia, you will have difficulty recalling facts, events, places, or specific details. The details can range from what you ate this morning to the name of the current president. You will still retain your motor skills, such as your ability to walk, as well as fluency in any languages you speak.

There are multiple types of amnesia, including retrograde amnesia, anterograde amnesia, and transient global amnesia.

The symptoms of amnesia depend on the cause, but generally include:

- Memory loss
- Confusion
- Inability to recognise familiar faces or places

- Once the person recovers, they typically have no memory of their amnesia episode.

Retrograde amnesia
When you have retrograde amnesia, you lose existing, previously made memories. This type of amnesia tends to affect recently formed memories first. Older memories, such as memories from childhood, are usually affected more slowly. Diseases such as dementia cause gradual retrograde amnesia.

Anterograde amnesia
When you have anterograde amnesia, you can’t form new memories. This effect can be temporary. For example, you can experience it during a blackout caused by too much alcohol. It can also be permanent. You can experience it if the area of your brain known as your hippocampus is damaged. Your hippocampus plays an important role in forming memories.

Transient global amnesia
Transient global amnesia (TGA) is a poorly understood condition. If you develop it, you will experience confusion or agitation that comes and goes repeatedly over the course of several hours. You may experience memory loss in the hours before the attack, and you will probably have no lasting memory of the experience. Scientists think that TGA occurs as the result of seizure-like activity or a brief blockage of the blood vessels supplying your brain. It occurs more frequently in middle-aged and older adults.

Infantile amnesia
Most people can’t remember the first three to five years of life. This common phenomenon is called infantile or childhood amnesia.

Diagnosis of amnesia
- Diagnosing the cause of amnesia involves a range of tests, including:
- Medical history
- General examination
- Tests for short and long term memory recall
- Other tests related to thought processing
- Head x-ray
- Blood tests
- Computed tomography (CT) scan

- Cerebral angiography (scans taken after a special dye is injected).

Causes of amnesia

Memory loss can be caused by a wide range of conditions, including:

- Head injury
- Severe illness
- High fever
- Seizures
- Emotional shock or hysteria
- Alcohol-related brain damage
- Certain drugs, such as barbiturates or heroin
- General anaesthetics
- Electroconvulsive therapy
- Stroke
- Transient ischaemic attack (a 'mini stroke')
- Alzheimer's disease
- Brain surgery.

  


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Dementia
A memory’s location in your brain is thought to depend on its age. To lose old memories, you must have widespread brain deterioration. This can be caused by Alzheimer’s disease or other forms of dementia. People with dementia usually lose more recent memories first and keep older memories longer.

Anoxia
A depletion of oxygen levels can also affect your entire brain and lead to memory loss. This condition is called anoxia. If the anoxia isn’t severe enough to cause brain damage, the memory loss can be temporary.

Damage to the hippocampus
Your hippocampus is a part of the brain and limbic system responsible for memory. Its activities include forming memories, organizing memories, and retrieving them when needed. Its cells are some of your brain’s most energy-hungry and fragile. They’re most easily disrupted by anoxia and other threats such toxins.

When your hippocampus is impaired, you will have difficulty forming new memories. If your hippocampus is damaged in both halves of your brain, you can develop complete anterograde amnesia.

Head injuries
Traumatic head injuries, as well as stroke, tumors, and infections, can also cause damage to your brain. This damage can include permanent memory problems. Concussions commonly disrupt memories of the hours, days, or weeks before and after you were injured.

Alcohol use
Short-term alcohol use can cause blackout. This is a temporary form of anterograde amnesia. Long-term alcoholism can cause Wernicke-Korsakoff syndrome. If you develop this condition, you will have difficulty forming new memories but may not be aware of it.

Trauma or stress
Severe trauma or stress can also cause dissociative amnesia. With this condition, your mind rejects thoughts, feelings, or information that you’re too overwhelmed to handle. A specific type of dissociative amnesia, called dissociative fugue, can lead to unexpected traveling or wandering. It can also lead to amnesia around the circumstances of traveling as well as forgetting other details of your life.


Electroconvulsive therapy
If you receive electroconvulsive therapy for depression or other conditions, you could experience retrograde amnesia of the weeks or months before your treatment. You could also experience anterograde amnesia, usually resolving within 2 weeks of the treatment.

How is amnesia diagnosed?
Amnesia can be diagnosed by your doctor or a neurologist. They will start by asking questions about your memory loss, as well as other symptoms you may have. They may ask a family member or caregiver to help with their evaluation, since you may not be able to remember the answers to their questions.

Your doctor may also use cognitive tests to check your memory. They may also order other diagnostic tests. For example, they may use an MRI or CT scan to check for signs of brain damage. They may use blood tests to check for nutritional deficiencies, infections, or other issues. They may also perform tests to check for seizures.

How is amnesia treated?

Treatment depends on the cause. For example, a person who has suffered a traumatic event may benefit from sedation, plenty of love and care, and (perhaps) psychiatric treatment. Concussion needs rest, once complications have been ruled out. If alcoholism is the cause, then abstinence, emotional support and addressing dietary deficiencies are recommended. In the case of Alzheimer's disease, a range of new medications that enhance the cholinergic function of the brain are now available; however, nursing homes or other extended care options may eventually be needed as the person becomes less able to look after themselves.

To treat amnesia, your doctor will focus on the underlying cause of your condition.

Chemically induced amnesia, from alcohol for example, can be resolved through detoxification. Once the drug is out of your system, your memory problems will probably subside.

Amnesia from mild head trauma usually resolves without treatment over time. Amnesia from severe head injury may not recede. However, improvements usually occur within six to nine months.

Amnesia from dementia is often incurable. However, your doctor may prescribe medications to support learning and memory.

If you have persistent memory loss, your doctor may recommend occupational therapy. This type of therapy can help you learn new information and memory skills for daily living. Your therapist can also teach you how to use memory aids and techniques for organizing information to make it easier to retrieve.

Preventing amnesia
The following healthy habits can lower your risk of blackouts, head injuries, dementia, stroke, and other potential causes of memory loss:

Avoid heavy use of alcohol or drugs.
Use protective headgear when you’re playing sports that put you at high risk of concussion.
Stay mentally active throughout your life. For instance, take classes, explore new places, read new books, and play mentally challenging games.
Stay physically active throughout your life.
Eat a heart-healthy diet, including fruits, vegetables, whole grains, and low-fat proteins.
Stay hydrated.

Source :

Health Line
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