Amnesia overview

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Zehra Malik, M.B.B.S[2]

Overview

Amnesia can be divided into two broad groups, retrograde amnesia and anterograde amnesia

Historical Perspective

Richard Semon in 1904 described that experiences cause some changes in the neurons and these changes are referred to as engram and they form memory of the particular experience in those neurons. Reactivation of these neurons occur when patient tries to recall those memories. Theodule-Armand Ribot, a French psychologist determined that memory loss affects recent memories first. Memories are lost in reverse order of their development.

Classification

Amnesia can be divided into two broad groups, retrograde amnesia and anterograde amnesia. Retrograde amnesia is the loss of memory prior to the onset of amnesia and anterograde amnesia is the inability to form new memory. Other types of amnesia are Psychological including repressive amnesia and dissociative fugue, infantile amnesia, neurological amnesia (Alzheimer's disease, Pick's disease), post-traumatic Amnesia, drug-Induced Amnesia, transient global amnesia. Memory can also be divided into two groups depending on the duration, short-term memory and long-term memory.

Pathophysiology

Amnesia results from damage to different memory centers in the brain, such as the medial temporal lobe and the hippocampus, which are involved in acquiring and restoring memory.

Causes

Common causes of amnesia include medications, head trauma, depression and aging.

Risk Factors

Aging, depression, chronic stress, head trauma, chronic sleep deprivation and medications are risk factors ​for amnesia.

Diagnosis

History and Symptoms

It is critical to perform a formal and exhaustive assessment of the patient to look for any indications of memory disorders and to hear any subjective complaints. With this information, preventative measures and care can be specifically addressed to the patient's needs.

Physical Examination

The physical examination includes a detailed test of thinking and memory (mental status examination or neurocognitive test), and an examination of the nervous system. Recent, intermediate, and long-term memory should be tested.

MRI

Psychogenic amnesia is defined by the lack of structural damage to the brain, but upon functional imaging, abnormal brain activity can be seen. Tests using functional magnetic resonance imaging suggest that patients with psychogenic amnesia are unable to retrieve emotional memories normally during the amnesic period, suggesting that changes in the limbic functions are related to the symptoms of psychogenic amnesia.[1]

Other Imaging Findings

By performing a positron emission tomography activation study on psychogenic amnesic patients with face recognition, it was found that activation of the right anterior medial temporal region including the amygdala was increased in the patient whereas bilateral hippocampal regions increased only in the control subjects, demonstrating again that limbic and limbic-cortical functions are related to the symptoms of psychogenic amnesia.[2] Transient global amnesia is distinct in that abnormalities in the hippocampus can sometimes be visualized using a special form of magnetic resonance imaging of the brain known as diffusion-weighted imaging (DWI).

Treatment

Medical Therapy

Treatment can be offered in cases of reversible conditions. If not, provision of supportive care can help to improve a patient's condition.

Surgery

Surgical intervention is not recommended for the management of memory loss.

Primary Prevention

Measures for the primary prevention of amnesia include preventing brain trauma, managing stress, avoid alcohol abuse, manage stroke risk factors, good sleep habits, social integration, optimum nutrition and exercise routine.

Secondary Prevention

Effective measures for the secondary prevention of memory loss include, sustainable daily routine, healthy eating habits, social integration, exercise routine, reduce and manage stress, adequate sleep, reading and playing strategic games like puzzles and word games.

References

  1. Yang JC, Jeong GW, Lee MS; et al. (2005). "Functional MR imaging of psychogenic amnesia: a case report". Korean J Radiol. 6 (3): 196–9. PMID 16145296.
  2. Yasuno F, Nishikawa T, Nakagawa Y; et al. (2000). "Functional anatomical study of psychogenic amnesia". Psychiatry Res. 99 (1): 43–57. PMID 10891648.


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