Amnestic disorders are mental conditions defined by loss of memory or inability to recall past information or retain new information in the memory and are characterized by disorientation to time and space, personality change, display of inappropriate emotions and possible confabulation. There are numerous forms of the amnestic disorders. However, the Diagnostic and Statistic Manual (DSM) of Mental Disorders categorizes them into three key areas as follows.
- Amnestic Disorder due to a General Medical Condition
- Substance Induced Persistent Amnestic Disorder
- Amnestic Disorder Otherwise Unspecified
Prevalence of amnestic disorders is difficult to assess. However, it is stated that people over the age of 40, with unhealthy lifestyles have a bigger risk of developing this disorder because of the declining physical state and also due to the fact that they have been exposed to a certain causative agent for longer than a person with lesser years. Studies have shown that those with relatives who have suffered from dementia, delirium, Alzheimer’s and amnesia are more likely to develop the condition, however the degree of correlation remains uncertain due to the lack of methodical documentation.
Amnesia, the Greek term for memory, has been used to indicate unconsciousness since very early days. There are two forms of amnesia, Anterograde amnesia and Retrograde amnesia. Anterograde amnesia is when the ability to form new memories declines, whereas retrograde amnesia is the inability to recall past details. Psychology has identified two forms of memory in humans, procedural and episodic. Procedural memories consist of memory of processes that are generally automated. (Playing piano, climbing stairs, dancing to music, etc) and episodic memory consists of the abstract facts that are placed together to form the personal identity or the type of memory that defines who we are. Most often only one type of memory gets impaired due to amnestic conditions. For example an individual may forget his personal identity but still remain a skilled pianist. But in certain are cases, both forms of memory can get affected and the individual’s daily functioning may decline rapidly.
Cause, Symptoms & Types
The most common cause for all forms of amnestic disorders is structural and chemical changes in the brain. The severity of the problem and form of the disorder varies according to the portion of the brain that has been affected. However, it is crucial to note that not in all cases of brain damage, can amnesia occur. Damage to brain tissue due to accidents, physical trauma, disease, infection, alcohol abuse or medicinal poisoning may either destroy the brain cells or block the blood flow to the brain (vascular insufficiency). Encephalitis and herpes are two physical disorders that are most likely to cause amnesia. However, it is crucial to note that amnesia may occur during the course of delirium or dementia but in such cases, the conditions are not labeled as an amnestic disorder. In other words, amnesia can be a symptom of disorders such as dementia and delirium. Recent studies have brought to light that exposure to harmful gases and radiation can also have a massive impact on amnesia. Constant contact with substances such as mercury, lead, carbon monoxide and insecticides can mutate the brain cells or damage them altogether, a phenomena similar to that occurring in the case of cancer, that can cause memory losses.
Symptoms of amnesia may vary from individual to individual. However, the key symptom is the loss of past memories and/or inability to form new memories. Disorientation to time and space, mood swings and inappropriate displays of emotions, changed personality and confabulations may also be other indication of the disorder. These symptoms should cause moderate to severe impairment in daily routines in the form of physical, social, emotional and cognitive misfits.
The types of amnestic disorders specified in the DSM as mentioned above are Amnestic Disorder due to a General Medical Condition, Substance Induced Persistent Amnestic Disorder and Amnestic Disorder Otherwise Unspecified. When an amnestic condition is brought about due to a general medical condition such as a physical trauma or illness, and cannot be attributed to any other form of dissociative disorders, it is considered as amnesia brought about due to general medical conditions. Transient global amnesia is when present memories are distorted, while the individual faces difficulties in recalling the past. It is one of the most damaging illnesses defined by neurology. It is known as Transient Global Amnesia during the first month of the medical condition and if the symptoms persist for over a month, it is recognized as Chronic Amnesia.
The second type of amnesia is substance induced amnesic conditions. Its symptoms are similar to those of general amnesia but the causes are substances such as alcohols, hypnotics, sedatives and anxiolytics. Neurological disturbances such as peripheral neuropathy, cerebellar ataxia and myopathy are some of the associated features of this form of amnesia. When the diagnostic criteria of amnesia don’t tally with the two types indicated above, it is diagnosed as an amnestic disorder which is otherwise unspecified.
Diagnosis and Tests
Amnestic Disorder due to a General Medical Condition
As stated above, the primary criteria for diagnosis should be the inability to form new memories and/ or the inability to recall the past. The condition should bring about impairments in the daily social and occupational routines of the individuals and should not be due to other mental conditions. Evidence indicating possible medical conditions are also necessary.
Substance Induced Persistent Amnestic Disorder
The diagnostic criteria are same as above expect for the fact that evidences related to substance inducement should be present. For example, prolonged drug abuse or overdoses of medication are key causes for this condition.
Amnestic Disorder Otherwise Unspecified
When the diagnosis doesn’t fit with the above, the amnestic disorder is categorized as having an unspecified cause.
Treatment Options & Care
Treatments for amnestic disorders are not highly effective. It is noted that time seems to cure or reduce certain symptoms of amnesia in some patients. About 3% of individuals to overcome amnesia have the risk of the condition recurring. A more practical approach to amnesia is to help sufferers function daily with the least difficultly by behaviors modification and group therapy. However, in the case of substance induced amnesia, thiamin is commonly used. Sufferers of amnesia need round-the–clock assistance to function in their daily lives and should be kept mentally active whenever possible.