Memory Digest

Amnesia

Amnesia is a loss of memory caused by brain injury, illness or emotional trauma; learn the main types, including brief "transient global amnesia," and how amnesia differs from dementia.

Last reviewed: October 2026

In movies, amnesia usually means someone wakes up with no idea who they are. Real life is different. Amnesia—also called amnestic syndrome—is a loss of memories, such as facts, information and experiences. As Mayo Clinic explains, most people with amnesia know who they are. Their main difficulty is learning new information and forming new memories.

The two main features

• Anterograde amnesia: trouble forming new memories after the illness or injury. This is the most common and often the most disabling part.
• Retrograde amnesia: trouble recalling memories from before the event. Recent memories are usually lost first, while older, deeply rooted memories—such as childhood experiences—are often kept.

Memory loss alone does not affect intelligence, general knowledge, attention, judgment or personality. People with amnesia can usually understand language and can still learn skills, such as riding a bike or playing piano, because skill memory relies on different brain systems. See Types of Memory.

Some people also experience confabulation—false memories that are invented or real memories misplaced in time—or confusion and disorientation, depending on the cause.

Amnesia is not the same as dementia

Dementia often includes memory loss, but it also involves declines in other thinking skills—language, judgment, visual-spatial skills—that interfere with daily life, and it usually gets worse over time. In amnesia, memory is the main problem, and it may be stable, improving or temporary depending on the cause. See What Is Dementia? and Mild Cognitive Impairment (MCI).

What causes amnesia?

Memory relies on a network of brain structures, especially the The Hippocampus in the temporal lobes and the thalamus deep in the brain. Damage to these areas can cause amnesia. According to Mayo Clinic and MedlinePlus, causes include:

• Stroke
• Brain inflammation (encephalitis), from infections such as herpes simplex virus or from autoimmune reactions
• Lack of oxygen to the brain, as after cardiac arrest, breathing failure or carbon monoxide poisoning
• Head injury—see Traumatic Brain Injury and CTE
• Wernicke-Korsakoff syndrome, caused by a severe shortage of vitamin B1 (thiamine), most often linked to long-term heavy alcohol use
• Seizures and brain tumors in memory-related areas
• Medicines, such as benzodiazepines and other sedatives—see Medications That Can Affect Memory
• Some treatments, such as electroconvulsive therapy (usually short-term memory loss) or certain cancer treatments
• Alzheimer's disease and related diseases—see Alzheimer's Disease

A rarer type, dissociative amnesia, results from severe emotional shock or trauma rather than physical brain damage. People may lose personal memories, and it usually doesn't last long.

Transient global amnesia (TGA)

Transient global amnesia is a sudden, temporary episode of memory loss that can be frightening to witness. According to Mayo Clinic:

• It most often affects people in middle or older age (risk is higher after 50 and in people with migraines).
• The person is awake, alert and knows who they are, but can't form new memories. They often ask the same questions over and over: "What am I doing here?"
• Episodes last no more than 24 hours and usually much less, and memory gradually returns.
• The cause is unknown. Possible triggers include sudden cold or hot water immersion, strenuous exercise, emotional upset or certain medical procedures.
• TGA itself isn't dangerous and is not a risk factor for stroke or epilepsy. Repeat episodes are uncommon.

However, sudden memory loss always needs emergency evaluation. There is no easy way to tell TGA from a stroke, seizure or other serious problem without medical testing. Call 911 if someone suddenly becomes confused or can't remember what just happened.

Diagnosis

A doctor will ask when and how the memory loss began, whether it is getting better or worse, and about head injuries, alcohol use, medications and other symptoms. Family and friends often provide key details. Tests may include:

• Memory and thinking tests—see Cognitive Screening Tests (MMSE, MoCA)
• Brain imaging (MRI or CT)
• Blood tests for infections, nutritional deficiencies (such as vitamin B1 or B12) and thyroid problems—see Vitamin B12 Deficiency and Memory
• EEG to look for seizure activity

Treatment and coping

There is no specific treatment for amnesia itself, but treating the underlying cause can help—for example, thiamine for Wernicke-Korsakoff syndrome, antiviral or immune therapies for encephalitis, or seizure medicines. Memory sometimes improves as the brain heals.

Practical strategies help people live with memory loss:

• Occupational therapy to learn new routines and memory strategies
• External memory aids: notebooks, calendars, smartphone reminders, labeled cabinets—see Memory Aids and Tools
• Written schedules for medicines and important tasks (MedlinePlus)
• Familiar photos, music and objects to support recall and comfort
• Support for families, who may need to provide supervision for safety

Prevention

Some causes can be prevented: limit alcohol, wear seat belts and helmets, treat infections promptly, and get emergency care for stroke symptoms such as a sudden severe headache or weakness on one side of the body (Mayo Clinic).

Bottom line

Amnesia means losing the ability to form new memories, recall old ones, or both. It has many causes—some treatable, some temporary—and is different from dementia. Any sudden or unexplained memory loss deserves prompt medical attention. Talk with a doctor about memory concerns rather than trying to diagnose them yourself.

Sources

1. Mayo Clinic: Amnesia – Symptoms and causes
2. Mayo Clinic: Transient global amnesia – Symptoms and causes
3. MedlinePlus (National Library of Medicine): Memory loss
4. MedlinePlus (National Library of Medicine): Wernicke-Korsakoff syndrome

Not medical advice. This article is general information, not a diagnosis or treatment plan for any individual. Talk with a doctor about your situation.

Related articles

• Types of Memory
• The Hippocampus
• How Memory Works: An Overview
• What Is Dementia?
• Traumatic Brain Injury and CTE