Memory loss is a common symptom of many neurological conditions. Although the exact mechanics of memory are not completely understood, anything that disrupts functioning of the brain has the ability to result in memory loss. Memory loss may be temporary or permanent, depending on the cause and the extent of damage (if any) to the brain.
Memory is usually described as being short-term or long-term. Short-term memory is the ability to store or recall information for a short period of time (e.g., a couple of minutes or hours). Long-term memory is the ability to store or recall information for indefinite periods of time.
Memory loss does not necessarily indicate a loss of intelligence or inability to make judgments. However, certain conditions that can cause memory loss may also cause cognitive disorders such as the loss of speech or inability to understand speech (aphasia), the loss of movement (apraxia) or the loss of the ability to recognize familiar people, places, objects or sensations such as smells (agnosia).
The term amnesia is sometimes used interchangeably with memory loss. There are two major types of memory loss that involve disease or injury to the brain. These are:
- Anterograde amnesia. The inability to form new long-term memories after a certain point in time (e.g., after a head injury).
- Retrograde memory loss. The loss of some or all long-term memories before a certain point in time (e.g., prior to a head injury).
Another, less common type of memory loss is called psychogenic memory loss. This involves a loss of memory, either short- or long-term, that is the result of emotional trauma. It is not related to physical damage to the brain.
Memory loss can be caused by many conditions, including:
- Alzheimer’s disease
- Head injury
- Parkinson’s disease
- Alcohol or drug abuse
- Tumors or brain lesions
- The use of certain medications
- Psychological trauma
Some instances of memory loss resolve without treatment. Memory loss that is caused by damage to the brain may be permanent and, although some medications are available to slow the progression of memory loss, there is rarely a cure. In some cases, treating the underlying disease or condition may resolve memory loss.
Many neurological conditions are poorly understood and no known prevention methods exist for these causes of memory loss. However, some causes of memory loss (e.g., head injury, substance abuse) may be prevented with appropriate self-care or avoidance techniques.
About memory loss
Memory is the process that occurs when the brain records and stores information. Memory can be divided into immediate (events that happened in the previous few seconds), intermediate memory (events that happened in the preceding seconds to last few days) and long-term memory (events that happened further back in time). In many cases, when people speak of short-term memory they are referring to immediate and intermediate memory.
Despite this process of recording information, most people forget things from time to time. When this forgetfulness occurs in a consistent pattern or involves impairment that affects a person’s ability to function, they are said to be experiencing memory loss (sometimes referred to as amnesia).
The exact mechanics of memory loss are not completely understood. However, memory loss can occur any time normal functioning of the brain is disrupted. Most often, memory loss is due to disease or physical injury to the brain. The extent of memory loss depends on the type and severity of injury or other cause of the memory loss.
Many areas of the brain are involved in memory storage and retrieval. The temporal lobe and frontal lobe (front part of the brain involved in cognitive function) are primarily responsible for storing and retrieving information. Emotions can also influence memory, which may involve the limbic system (brain structures involved in emotion and motivation, such as the hypothalamus, hippocampus and amygdala). Several large networks of neurons (nerve cells) connect different parts of the brain involved in memory storage and retrieval. Because memory involves so many different areas of the brain, almost any kind of brain damage can cause memory loss.
Short-term memory is stored in the temporal lobe of the brain. This area may be affected in certain degenerative disorders (e.g., Alzheimer’s disease). Long-term memory is stored in both the temporal and parietal lobes of the brain. The parietal lobe may become affected in later stages of some degenerative neurological conditions.
Memory loss is a common symptom of many neurological conditions. It is especially common in people with dementia and people with head injuries. In some cases, memory loss is temporary, lasting from a couple of minutes to several hours before disappearing on its own. However, when memory loss is caused by severe brain damage or certain degenerative neurological conditions, it may be permanent and worsen over time.
The specific cause of a patient’s memory loss will determine whether it is temporary or permanent. For example, a type of memory loss called transient global amnesia is strictly temporary. The cause of a patient’s memory loss will also determine whether the memory loss appears suddenly (as in the case of transient global amnesia) or occurs gradually, over a period of time (e.g., in cases of dementia).
Memory loss can affect a patient’s ability to remember events of the past, as well as behaviors or skills previously learned. This may impact a patient’s ability to function on a daily basis, depending on the severity and type of memory loss.
Memory loss is often associated with old age. However, it is important to note that mild memory loss associated with aging is not the same as the often severe memory loss associated with medical conditions such as Alzheimer’s disease and dementia, which are more prevalent among older adults.
Other symptoms related to memory loss
People who experience memory loss may also experience other symptoms at the same time. These additional symptoms may be the result of brain damage that not only affects memory, but other functions as well. For example, behavioral and personality changes (e.g., irritability, confusion, moodiness) may occur alongside memory loss in patients with dementia.
Additional symptoms are sometimes related to psychological conditions that may be causing the memory loss. For example, patients with post-traumatic stress disorder may experience anxiety, nightmares and insomnia in addition to memory loss.
There are many additional symptoms that can occur in patients with memory loss. Some of these other symptoms include:
- Aphasia. Inability to communicate and understand language. When certain areas of the brain become damaged, patients may forget words and have difficulty communicating with or understanding others. This symptom may accompany memory loss in many different neurological conditions, including brain tumors and Alzheimer’s disease.
- Apraxia. Loss of motor function. This symptom is usually progressive when it occurs in patients with neurological conditions. Apraxia may occur with memory loss in conditions such as dementia and head injuries.
- Seizures. Involuntary muscle contractions due to excessive electrical activity in the brain. Memory loss and seizures may occur together, such as in some cases of epilepsy and substance abuse.
- Agnosia. Inability to recognize familiar people, objects or sensory information. For example, a patient experiencing agnosia may be unable to recognize signals from the body, such as when the bladder is full, certain smells or pain signals. Agnosia is a relatively rare symptom, although it may occur with memory loss in some instances, such as in some cases of stroke.
Types and differences of memory loss
As a symptom, memory loss can occur in many different forms. Memory loss may be temporary or permanent. It can last for brief periods of time (e.g., for several hours) or it can last for longer periods of time (e.g., days, months, years). Impairment can be partial or complete. It can involve short-term memory loss (inability to remember or store recent events), long-term memory loss (inability to remember events that occurred in the past), or both. It can also involve the inability to store new information into memory.
There are two major types of memory loss caused by disease or injury to the brain. These are:
- Anterograde amnesia. The inability to store or recall new events and information – those occurring after the moment of brain damage. Patients with anterograde amnesia typically struggle to remember day-to-day events, but have less difficulty remembering events from their childhood. It is thought that anterograde memory loss is caused by damage to the hippocampus, a structure located in the temporal lobe of the brain. The hippocampus is known as the gateway to memory. Research has shown that memories stored in the hippocampus are permanently retained. Thus, patients with damage to the hippocampus may have difficulty storing new memories.
- Retrograde amnesia. The inability to recall events and information that occurred prior to the moment of brain damage. Most cases of retrograde amnesia involve memory loss of events directly preceding the brain injury. This is often the case for people involved in automobile accidents who cannot remember the events that led to the accident. In some cases, retrograde amnesia involves the loss of all memories that occurred before brain damage, including those from childhood and memories of family and friends.
Transient global amnesia is another type of memory loss. It is believed to be related to either a transient ischemic attack (mini-stroke) or a seizure without convulsive activity. This type of memory loss is temporary and may involve both anterograde and retrograde amnesia.
A less common type of memory loss is psychogenic amnesia. This is also called dissociative amnesia because certain mental processes (e.g., memory) become separated from the rest. Psychogenic amnesia is psychological in origin. It is not caused by physical injury or disease of the brain, nor does it involve any disruption of brain functioning. Psychogenic amnesia is often the result of severe emotional trauma that may be too distressing for a person to recall. It tends to appear in the form of localized amnesia, which affects all memories during a particular period of time. This type of memory loss usually appears suddenly, is temporary, and may be resolved with therapy.
There are many different subtypes of psychogenic memory loss (e.g., localized amnesia, selective amnesia, generalized amnesia, systematized amnesia). For example, the memory loss associated with post-traumatic stress disorder (PTSD) may be considered a type of psychogenic memory loss.
Potential causes of memory loss
Memory loss can be caused by anything that disrupts normal functioning of the brain. This is usually due to disease or head injury. Conditions that may cause memory loss include:
- Alzheimer’s disease, dementia. A disease of the brain that gets worse over time. It is the most common cause of dementia among people over the age of 65, according to the National Institute of Neurological Disorders and Stroke. Both conditions involve the death of neurons (nerve cells) in the brain or loss of their ability to connect with other neurons. When this affects neurons or parts of the brain associated with memory, memory loss can occur. Anterograde amnesia is one of the first symptoms of Alzheimer’s disease. As the disease progresses, patients may also permanently lose long-term memory, become unable to understand language, and may even forget how to swallow.
- Head injury. Physical injury to the head may include damage to parts of the brain that affect memory. Head injuries can have a variety of causes, including car accidents, falls, sports mishaps and brain surgery. People with head injuries often experience memory loss of events immediately preceding the injury (retrograde amnesia). Sometimes these memories are never recovered. People with severe brain injuries may experience permanent memory loss and have trouble forming memories for the rest of their life. Head injuries rarely result in memory loss that gets progressively worse (as is seen in certain degenerative neurological conditions, such as dementia).
- Epilepsy. Epilepsy is a neurological disorder that involves a tendency to experience disruption of electrical activity in the brain that causes recurring seizures. Epilepsy may be caused by brain injury, certain medical conditions (e.g., cerebral palsy) or genetics, although in many cases the cause is unknown. People with epilepsy may experience damage or disruption of brain functioning that can result in memory loss. This is especially true for people who have seizures that affect the temporal lobe, which is thought to be critical for memory storage.
- Parkinson’s disease. Parkinson’s disease is chronic, progressive disease in which patients lose brain cells that produce the neurotransmitter dopamine, which helps to regulate movement. As a result, it causes several characteristic symptoms, including tremors, slowness of movement and rigidity. It can also cause memory loss.
- Substance abuse. Alcohol is believed to damage the hippocampus, a brain structure involved with memory storage. Even relatively minor alcohol intake can cause memory loss to a certain extent. People who drink large quantities of alcohol over a long period of time can develop a condition called Wernicke-Korsakoff syndrome. This syndrome is caused by a lack of thiamine – a common vitamin deficiency in alcoholics – and may cause permanent memory loss. In addition, the abuse of certain drugs, (e.g., barbiturates, hallucinogens), can alter brain chemicals and make it more difficult for a person to recall memories.
- Stroke. A stroke is a life-threatening event in which part of the brain is deprived of adequate oxygen (hypoxia). Also known as a cerebrovascular accident (CVA) or a “brain attack,” a stroke occurs when a blood vessel in the brain bursts or becomes clogged by a blood clot or other mass. This prevents oxygen and nutrients from getting to nerve cells in the affected area of the brain. These nerve cells can die within minutes, and the area of the body that they control can cease to function. In many cases, this damage is permanent, especially if the patient is not treated immediately.
- Brain tumors or lesions. Tumors or brain lesions, which can cause pressure to build in the brain, can disrupt the function of neurons, leading to memory loss. In some cases, removal of the tumor or lesion may restore memory function, although sometimes the memory loss may be permanent.
- Side effects of certain medications. Some medications, particularly sedatives such as benzodiazepines and anticholinergics, may cause temporary memory loss.
- Psychological trauma. Severe emotional distress can cause psychogenic amnesia, a type of memory loss that is psychological in origin (no brain injury or damage is present).
Many additional conditions can cause memory loss. This includes certain infections (e.g., encephalitis, meningitis, syphilis, HIV), degenerative diseases (e.g., Huntington’s disease) and brain disorders (e.g., Creutzfeldt-Jakob disease). Additional causes of memory loss may include malnutrition and exposure to toxins.
Treatment options for memory loss
Many cases of memory loss resolve without treatment after a period of time. This is especially the case when memory loss is caused by mild to moderate head injuries (such as concussions) where the brain is able to recover after a short period of time.
Memory loss may be permanent when it is caused by severe head injuries or degenerative neurological conditions such as Alzheimer’s disease. In these cases, it may be possible to treat memory loss enough to enable a patient to function without requiring caregivers.
Medications used to treat cognitive loss (which includes loss of memory) may include:
- Cholinesterase inhibitors. This type of medication is often prescribed for Alzheimer’s disease and other disorders that cause damage to the basal forebrain (group of structures near the bottom front of the brain). It maintains levels of the neurotransmitter acetylcholine in the brain, which is essential for memory, judgment and learning.
- N-methyl D-aspartate receptor antagonists (NMDAs). These drugs work by regulating the amount of another neurotransmitter called glutamate, which is also important for memory and learning. If there is too much glutamate in the brain, it can overstimulate parts of the brain and cause the disruption and death of neurons.
In addition, the herbal supplement ginkgo biloba is claimed to have a beneficial effect on memory. It also acts as an antioxidant (substance that inhibits cellular damage) in the body. Ginkgo biloba is a popular supplement in the United States, although its claims have not been substantiated by science and it is not regulated by the Food and Drug Administration.
For memory loss caused by other neurological conditions (e.g., epilepsy, brain tumor), treating the underlying cause may resolve a patient’s memory loss. This may include the use of certain medications or surgery.
If memory loss is caused by substance abuse or as a side effect of certain medications, eliminating the substance or medication may resolve a patient’s memory loss. Patients are advised to consult their physician before discontinuing any current medications. In addition, people with substance abuse problems may wish to consult a physician about how best to stop their behavior, especially since withdrawal symptoms may include memory loss.
Psychological counseling may help resolve memory loss for people who experience psychogenic amnesia.
Patients with permanent memory loss may find memory aids useful. This can include using beeping watches or sticky notes as reminders for certain tasks. In some cases, people with conditions that result in degenerative memory loss may benefit from living in a structured environment such as long-term care facilities.
Prevention methods for memory loss
Many of the neurological conditions that can cause memory loss are poorly understood and have no known prevention methods.
There are certain measures people can take to prevent head injuries, which are a common cause of memory loss. Appropriately protecting the head in different situations can be an effective way to reduce the risk of sustaining head injuries. For example, people should always wear seat belts and children should be placed in appropriate restraining devices when traveling in a car. Protective head gear should be worn during many different sports or activities. This includes contact sports such as football and hockey, as well as when riding a bicycle, horse or rollerblading.
Some studies have shown that oxidative stress, the process of cell damage by free radicals, contributes to the risk of developing Alzheimer’s disease, which results in memory loss. Oxidative stress may be prevented by consuming foods that are high in antioxidants (substances that prevent cellular damage in the body), including olive oil, fish and fresh fruit and vegetables. Oxidative stress may also be prevented by taking supplements of vitamins A, C and E, although a physician should always be consulted before starting to take any type of dietary supplement.
It is also becoming clear that keeping the brain healthy is helped by remaining physically and mentally active throughout life, especially in later life. Physical and mental activity may reduce the risk of memory loss as well as keep the body healthy.
Questions for your doctor about memory loss
Preparing questions in advance can help patients and their loved ones have more meaningful discussions with healthcare professionalsregarding their condition. Patients or their friends and family members may wish to ask their doctor the following questions related to memory loss:
- What type of memory loss is involved in this case (e.g., retrograde amnesia, anterograde amnesia, psychogenic amnesia, transient global amnesia)?
- Does it affect short-term or long-term memory? Will it be temporary or permanent?
- What do you think caused this memory loss?
- Does this memory loss indicate brain damage? If so, is the damage reversible?
- Can the memory loss be stopped or prevented from worsening?
- What treatments do you recommend? What are their benefits and risks?
- Are there any over-the-counter remedies or dietary supplements you recommend?
- Will surgery be able to resolve this memory loss?
- Are some memories likely never to be restored? How will this affect daily life?
- What day-to-day precautions do you recommend because of this memory loss?
- Do you recommend psychotherapy?