Anterograde amnesia is a disorder of long—term memorization of events occurring after the occurrence of pathological changes. It is characterized by forgetting places, people, events while preserving current memory and memories of the past. The clinical picture shows symptoms typical of the underlying disease. Diagnosis is carried out according to anamnesis, neurological examination, cognitive testing, results of toxicological analysis, neuroimaging, brain hemodynamics research. Treatment is mainly medical, includes nootropic, vascular, antioxidant agents. It is possible to prescribe memantins, anticholinesterase drugs.
R41.1 Anterograde amnesia
Anterograde amnesia is one of the main types of memory disorders, mnestic disorders in which capture the period after the occurrence of a causal disease or the impact of a traumatic factor. “Anterograde” (from the Latin words anterius — “before”, gradis — “to go”) means “moving forward”. The term was coined in 1881 by the French psychologist Theodule Ribot. Much later, in 1984, a model of system consolidation was proposed to explain the role of the hippocampus in memory processes. Later, this model formed the basis of the theory of the pathogenesis of anterograde amnesia. This type of amnesia occurs at any age. A higher frequency in the elderly is associated with the presence of vascular pathology, degenerative processes.
The brain is a rather fragile structure, subject to the negative influence of a wide range of physical, metabolic, and mental factors. Triggers of the anterograde type of amnesia can be any adverse effects on the cerebral tissues, leading to a violation of the interneuronal connections involved in memorization. Among the main etiological reasons are:
- Traumatic brain injuries. Severe concussions, brain contusions occur with combined memory lesions. Anterograde amnesia is combined with congrade and retrograde.
- Degenerative processes of the central nervous system. Senile dementia, Alzheimer’s disease are accompanied by progressive atrophic changes in the cerebral cortex, entailing disorders of the functioning of various types of memory.
- Cerebrovascular pathology. Acute and chronic insufficiency of cerebral blood supply, caused by hypertension, atherosclerosis, vascular abnormalities, leads to hypoxia and insufficient supply of neurons with nutrients, which negatively affects their functioning. Along with memory, other cognitive functions also suffer.
- Cerebral neoplasms. Intracranial neoplastic processes destroy brain structures and connections between neurons due to germination in them or compression.
- Intoxication. Alcoholism, drug addiction, acute carbon monoxide poisoning, and other toxic effects on cerebral tissues lead to morphological and functional disorders, including amnesia. A well-known example is the Korsakov syndrome.
- Neuroinfections. Infectious and inflammatory processes of the cerebral substance, meningitis with a transition to the cerebral cortex lead to neuronal dysfunction of the affected area with the possible occurrence of anterograde amnesia.
- Mental disorders. Hysteria, schizophrenia, obsessive-compulsive neurosis can occur with memory loss for certain events of the recent past.
- Taking benzodiazepines. Against the background of taking pharmaceuticals of this group, it is possible to develop anterograde amnesia with the preservation of short-term memory. The information stored before the start of the reception is not lost.
The mechanisms of memorization, recall and the morphological structures responsible for them have not been fully studied. Experiments on animal models have suggested that short-term memorization of new information is carried out with the participation of the hippocampus. Then a so-called “trace” is formed between the hippocampus and the neocortex, and short-term information is transferred to long-term storage. The morphological basis of this process are neurons, axon-dendral and axon-somatic synapses.
Variable etiofactors that cause damage or dysmetabolic disorders of brain tissue disrupt interneuronal connections, the formation of a cortical “trace” is partially or completely blocked. As a result, the transition of short-term memory into long-term memory is disrupted, anterograde amnesia occurs.
Macro- and microscopic changes in the brain correspond to the cause of the disease. They may include post-traumatic necrotic foci, hemorrhages, ischemic zones, inflammatory changes, atrophic areas, neoplastic invasion. In some cases, morphological abnormalities are not detected, the pathological process occurs at the functional level.
It is characterized by the absence of memories of events that occurred after the onset of the disease. Patients are oriented in the present, recognize familiar surroundings, familiar people, easily find their way home. The ability to remember current information is not impaired. Mnestic deviations are detected by chance, are unexpected for the patient himself. For example, after visiting a new place, the patient retains memories of it for some time, but after a few days he completely forgets. Returning to the place where he lived for several weeks, he does not recognize either the people or the situation, he absolutely does not remember the events that happened to him.
Memories of the period of life before the development of the disease are preserved in full. Therefore, patients are distrustful of the first episodes of revealing the absence of memories, do not believe others. However, repeated cases convince them to seek medical help.
Concomitant symptoms depend on the etiology. Vascular lesions are accompanied by increasing cerebral manifestations, episodes of transient ischemia. With encephalitis, hyperthermic syndrome is often noted. For degenerative processes, an aggravating cognitive deficit is typical. Cerebral tumors occur with focal symptoms: paresis, visual disorders, speech disorders.
Korsakov syndrome is characterized by a combination of anterograde and fixation amnesia, patients fill the absence of real memories with confabulations. With the psychogenic nature of the disease, episodic amnesia is typical, strict selectivity is possible — the absence of memories of certain events.
The presence of anterograde amnesia causes the patient a state of psychological discomfort, self-doubt, and his abilities. The disease negatively affects professional qualities, with progression deprives the patient of the opportunity to work. Without adequate psycho-neurological assistance, the above can lead to the development of a serious mental disorder (depression, neurosis).
Diagnostic measures begin with the collection of anamnesis with the participation of the patient’s relatives. The neurologist carefully analyzes information about the loss of memories, the time of their appearance, duration, connection with trauma, psychogenic factor, disease.
Evaluation of the mnestic function is carried out by special testing. The data of the neuropsychiatric study make it possible to identify pathological changes corresponding to the causal disease: focal symptoms, cognitive disorders, behavioral reactions, changes in the psyche. If necessary, a psychiatrist is consulted. The list of additional examinations depends on the suspected underlying disease, may include:
- Chemical and toxicological analysis of blood. It is necessary to exclude the toxic etiology of anterograde amnesia. It includes the determination of alcohol, narcotic substances, individual medications, and their concentration.
- Neuroimaging. Allows you to identify traumatic injuries, hematomas, ischemic areas, neoplasms, atrophic changes. CT brain is most informative in patients with injuries, MRI — in the diagnosis of vascular foci and degenerative diseases.
- Investigation of cerebral blood flow. It is performed using angiography, ultrasound of the vessels of the head and neck, duplex scanning. It is necessary if the presence of cerebrovascular disorders is suspected.
- Lumbar puncture. It is carried out for the purpose of collecting cerebrospinal fluid. The study of the composition of liquor, its bacteriological culture is required to exclude the infectious etiology of anterograde amnesia.
Differentiation is carried out with other types of memory loss. The period of loss of memories is important. With retrograde amnesia, it precedes the onset of the disease, with congrade, it includes only a period of altered consciousness (the moment of epiprime, a state of affect, oneiroid). Fixation amnesia, unlike anterograde amnesia, occurs in relation to current events, accompanied by disorientation in time, situation. However, it should be remembered about the possibility of combined disorders of mnestic function in the form of a combination of retrograde and fixation amnesia with anterograde.
Therapy is aimed at eliminating the etiological cause, restoring the normal functioning of nervous structures, and rehabilitating the patient’s mnestic abilities. In the psychogenic form, psychotherapeutic treatment with the use of psychoanalysis, cognitive behavioral techniques is necessary. All patients are shown complex pharmacotherapy to improve cerebral metabolism, maintain the functioning of neurons in pathological conditions. The main medicinal products are:
- Nootropics. Improve cognitive functions by potentiating the metabolism of neurons, their functional activation. They are most effective in vascular disorders, post-traumatic conditions.
- Ginko biloba extract. The components of the drug synergistically support homeostasis of nervous tissue, carry out neuroprotection. In clinical trials in patients with neurodegenerative diseases, it has been proven to cause temporary stabilization of the pathological process.
- Antioxidants. By inhibiting oxidants and free radicals, they reduce the degree of damage to neurons in inflammatory, vascular, and traumatic lesions.
- Acetylcholinesterase inhibitors. In the course of scientific research, it has been established that drugs of this group reduce the degree of mnestic disorders in Alzheimer’s type dementia. However, the effectiveness varies in different patients.
- Mementines. It has been proven to improve cognitive abilities in Alzheimer’s disease. The ability to influence the process of neurodegeneration has not been proven.
- Vascular pharmaceuticals. They are prescribed if necessary to improve cerebral hemodynamics.
- Detoxification. It is carried out in acute and chronic intoxication by the use of sorbents, intravenous injections of detoxification solutions.
Prognosis and prevention
The possibility of memory recovery in anterograde amnesia depends on the type and success of treatment of the underlying pathology. Post-traumatic changes of moderate severity, acute intoxication, neuroinfections, psychogenic forms in young patients have a favorable prognosis. Degenerative changes lead to a steady progression of mnestic dysfunction. Preventive measures include prevention of exposure to etiofactors: prevention of injuries, vascular pathology (hypertension, atherosclerosis), neuroinfections. The use of toxic substances should be avoided.