Generality
Retrograde amnesia is a disorder characterized by the inability to remember events or information acquired before a pathological event .
In this form of memory loss, the patient has complete lucidity for all that has happened following the onset of the disease and has no difficulty in memorizing new information.
The causes of retrograde amnesia are to be found in the brain and may include traumatic lesions, vascular accidents, degenerative processes and metabolic disorders.
The diagnosis of this form of amnesia is based on the collection of anamnestic data and is formulated following a psychological evaluation and a neuroradiological examination (eg computerized tomography, magnetic resonance, etc.).
Some cases of retrograde amnesia are temporary, others are permanent . Therefore, the manifestations related to the disorder can improve, remain the same or gradually worsen with time.
Treatment of retrograde amnesia is directed to the cause and focuses on problem management. Usually, the interventions include a psychotherapeutic course, sometimes in combination with other techniques or approaches to improve the quality of life of the patient (eg specific exercises, memory aids or dietary supplements).
What's this
What is Retrograde Amnesia?
Retrograde amnesia is a memory disorder characterized by a partial or total inability to recover information or events prior to the onset of a morbid event.
In practice, the patient cannot remember what was already part of the mnesic heritage (this is why the disorder is also called " re-enactment amnesia ") before brain damage, but presents a complete lucidity for what happens later.
The extent of the memory gap is variable and can be limited to a few minutes or expand to several decades of life. In general, however, remote memories are better preserved than more recent ones.
Causes and Risk Factors
Retrograde amnesia is a memory deficit that fundamentally depends on brain damage . Because of this event, the patient has serious difficulty recovering memories prior to the illness or the triggering event, while the ability to store new information remains unchanged.
In retrograde amnesia, the mnemonic gap essentially concerns autobiographical memories, while it does not concern professional gestures and social behaviors.
Retrograde amnesia may be the consequence of a traumatic brain injury . At other times, the disorder is the result of an acute event such as a cerebral ischemia, a heart attack, oxygen deprivation ( hypoxia ) or an epileptic attack . Less commonly, retrograde amnesia can also be caused by shock, emotional disturbance, alcohol intoxication or the use of some drugs.
In the learning process, memory - understood as a method of preserving information - plays an essential role. It may happen that we do not remember some events of our life that happened a long time ago or yesterday, but, when brain injuries occur, the loss of memories can be more serious, defining a clinical picture of AMNESIA .
What parts of the brain are involved?
The elaboration of the memories includes the recording (acquisition of new information), the codification (formation of associations, temporal markings and other processes necessary for recovery) and the commemoration . An alteration of any of these phases can cause amnesia.
The parts of the brain most commonly affected by damage at the origin of retrograde amnesia are those on which the functions of episodic and declarative memory depend: the diencephalon, the ppocampus and some areas of the temporal lobe .
- IPPOCAMPO is the structure dedicated to the consolidation of memory . More in detail, it is a "passage" area, in which information is coded and stored temporarily, until it is transmitted to the frontal lobe for future retrieval ( long-term memory ). The hippocampus is, therefore, a sort of archive for short memory (ie the one capable of keeping a few elements, for a few seconds) and, if it does not behave as such, it will be difficult or impossible to store memories.
- The role of DIENCEFALO and surrounding areas in retrograde amnesia is not yet well understood. However, this structure seems to be involved in the memory of autobiographical facts, inserted in a precise temporal and spatial context .
- In addition to helping the hippocampus consolidate memories, TEMPORAL LOBES are extremely important for semantic processing and retrieval of information related to past events. Damage to this region of the brain can lead to alterations in verbal functions (eg language organization, understanding disorder and difficulty in studying) and long-term memory impairment .
If brain damage is limited, NEUROPLASTICITY (ie the brain's ability to re-map neural connections or search for alternative pathways to avoid injured areas) may allow the patient suffering from retrograde amnesia the opportunity for normal (or almost ), for memorizing memories. Clearly, this is only possible to a certain extent.
Other brain structures, including the Wernicke area and the neocortex, also participate in the recovery of older and consolidated memories over time, through alternative routes.
Retrograde Amnesia: which pathological conditions do you associate with?
Retrograde amnesia is often the consequence of:
- Severe head injury;
- Cerebrovascular problems (like an aneurysm);
- Epilepsy ;
- Brain ischemia or hypoxia (due to stroke or other conditions that result in a reduced blood oxygen supply);
- Carbon monoxide intoxication .
Other conditions that can cause retrograde amnesia include:
- Cardiac and respiratory arrest;
- Lobectomy (neurosurgical intervention usually performed to treat severe, drug-resistant seizures);
- Infectious diseases (herpes simplex virus encephalitis, meningitis, etc.);
- Brain hemorrhages;
- Chronic alcohol abuse;
- Korsakoff syndrome (vitamin B1 deficiency);
- Brain tumors of diencephalic areas and temporal lobes;
- Some drugs;
- Dementia and neurodegenerative diseases;
- Electroconvulsive therapy (ECT).
Symptoms and Complications
The main symptom of retrograde amnesia is memory loss . The deficit concerns, in a particular way, the memory of events that took place before the causal event ( re-enactment defect ).
Retrograde amnesia tends to negatively influence the episodic part of declarative memory, which coincides with the recollection of facts accessible to awareness, referred to autobiographical information, inserted in a temporal and / or spatial context.
The disorder keeps the procedural memory intact (that is, the learning of skills and habits, of how things are done and how objects are used), without difficulty in registering and recalling new knowledge . From the triggering moment onwards, therefore, those suffering from retrograde amnesia can remember and manage with clarity everything that happens.
Memory loss can extend into the past for a period ranging from several minutes to life . Sometimes, however, the mnemonic gaps of retrograde amnesia can manifest themselves with a temporal gradient, so that remote events are remembered better than recent ones.
Retrograde Amnesia: how it occurs
The symptoms of anterograde amnesia depend on the cause from which it derives and mainly concern the processing of long-term memory (that is, memories that persist over time).
In general, those affected by this form of memory loss are more likely to lose memories closer to the traumatic incident or to the onset of the disease, compared to more remote memories.
The type of forgotten information can be very specific (for example, amnesia may relate to a single event) or more general.
Unlike the anterograde amnesia, this form of memory loss affects, therefore, the memories that were already part of the memory heritage and does not affect the storage of new information from the onset of the morbid event onwards.
Duration of the disturbance
Retrograde amnesia can be:
- Transient : the loss of memory is temporary and the extent of the mnemonic gap is progressively reduced, to limit itself to short-term forgetfulness; therefore, patients affected by transient retrograde amnesia recover most of the memories, as often happens after mild brain trauma;
- Stable : occurs after a severe morbid event, such as an encephalitis, a global ischemia or a cardiac arrest;
- Progressive : this form occurs mainly in the Korsakoff syndrome and in dementias on a degenerative basis, such as Alzheimer's disease.
The recovery of normal functions differs with regard to time (from days to decades) and the contents of memories (some patients will remember only specific cases, others more details or episodes).
Diagnosis
The diagnosis of retrograde amnesia is based on clinical, psychiatric and neurological evaluation .
Initially, the patient is subjected to an interview concerning autobiographical facts (verified with the contribution of a well-informed family member) and simple tests are performed (eg recall of three words, location of objects previously hidden in the room, learning of a word list etc.).
The clinical findings generally suggest the causes of retrograde amnesia and which tests are needed to investigate the clinical picture.
The investigations aimed at defining the condition include:
- Specific neurological tests: they are useful to better understand the nature of the amnesic experience;
- Magnetic resonance : evaluates the presence of possible structural causes;
- PET (positron emission tomography) : is a survey that highlights the metabolic alterations of the brain;
- Blood and urine tests : make it possible to exclude intoxication, the use of psychotropic substances or treatable metabolic causes.
Treatment and Remedies
Treatment of retrograde amnesia fundamentally depends on the cause of the problem. Some patients recover their memories and the condition tends to resolve spontaneously, especially if appropriate assistance measures are arranged. Other people suffering from retrograde amnesia, on the other hand, fail to return to normal and their daily routine is strongly influenced by the disorder.
Retrograde Amnesia: what are the possible interventions?
Treatment of retrograde amnesia focuses on improving the patient's quality of life.
Options include:
- Memory training;
- Food supplements based on vitamin B1, in case of a possible deficiency;
- Occupational therapy;
- Psychotherapy;
- Technological assistance to facilitate mnemonic recovery.
At the moment, there are no medicines approved to treat retrograde amnesia, but the use of drug therapy may be indicated by the doctor to reduce anxiety-depressive symptoms, irritability and insomnia, hyperactivation and disorganization of thought. Among the most used medicines there are: antidepressants, anxiolytics, antipsychotics and neuroleptics.
In less severe cases, patients are educated to use alternative memory systems to compensate for the deficit. For example, it may be helpful to note the activities to be performed daily on small boards or notebooks.
