Amnestic Disorders is characterized by cognitive impairment involving an inability to form new memories and an inability to recall old memories.
The amnestic disorders are a group of disorders that involve loss of memories previously established, loss of the ability to create new memories, or loss of the ability to learn new information. As defined by the mental health professional's handbook, the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, text revision (2000), also known as DSM-IV-TR, the amnestic disorders result from two basic causes: general medical conditions that produce memory disturbances; and exposure to a chemical (drug of abuse, medication, or environmental toxin). An amnestic disorder whose cause cannot be definitely established may be given the diagnosis of amnestic disorder not otherwise specified.
The amnestic disorders are characterized by problems with memory function. There is a range of symptoms associated with the amnestic disorders, as well as differences in the severity of symptoms. Some people experience difficulty recalling events that happened or facts that they learned before the onset of the amnestic disorder. This type of
amnesia is called retrograde amnesia. Other people experience the inability to learn new facts or retain new memories, which is called anterograde amnesia. People with amnestic disorders do not usually forget all of their personal history and their identity, although memory loss of this degree of severity occurs in rare instances in patients with dissociative disorders.
In addition to problems with information recall and the formation of new memories, people with amnestic disorders are often disoriented with respect to time and space, which means that they are unable to tell an examiner where they are or what day of the week it is. Most patients with amnestic disorders lack insight into their loss of memory, which means that they will deny that there is anything wrong with their memory in spite of evidence to the contrary. Others will admit that they have a memory problem but have no apparent emotional reaction to their condition. Some persons with amnestic disorders undergo a personality change; they may appear apathetic or bland, as if the distinctive features of their personality have been washed out of them.
Some people experiencing amnestic disorders confabulate, which means that they fill in memory gaps with false information that they believe to be true. Confabulation should not be confused with intentional lying. It is much more common in patients with temporary amnestic disorders than it is in people with long-term amnestic disorders.
Transient global amnesia (TGA) is characterized by episodes during which the patient is unable to create new memories or learn new information, and sometimes is unable to recall past memories. The episodes occur suddenly and are generally short. Patients with TGA often appear confused or bewildered.
DSM-IV-TR specifies three general categories of amnestic disorders. These are: amnestic disorder due to a general medical condition, substance-induced persisting amnestic disorder, and amnestic disorder not otherwise specified. The basic criterion for diagnosing an amnestic disorder is the development of problems remembering information or events that the patient previously knew, or inability to learn new information or remember new events. In addition, the memory disturbance must be sufficiently severe to affect the patient's social and occupational functioning, and to represent a noticeable decline from the patient's previous level of functioning. DSM-IV-TR also specifies that the memory problems cannot occur only during delirium, dementia, substance use or withdrawal.
Amnestic Disorder Due to a General Medical Condition.
There are no treatments that have been proved effective in most cases of amnestic disorder, as of 2002. Many patients recover slowly over time, and sometimes recover memories that were formed before the onset of the amnestic disorder. Patients generally recover from transient global amnesia without treatment. In people judged to have the signs that often lead to alcohol-induced persisting amnestic disorder, treatment with thiamin may stop the disorder from developing.