neurologic disorders
Amnesias
Introduction
Amnesia is partial or total inability to recall past experiences or inability to store new memoriesafterthe causative event. It may result from traumatic brain injury, degeneration, metabolic disorders, seizures, or psychologic disturbances. Diagnosis is clinical but often includes neuropsychologic testing and brain imaging (eg, CT, MRI). Treatment is directed at the cause. Processing of memories involves the following: Registration (taking in new information) Encoding (forming associations, time stamps, and other processes necessary for retrieval) Retrieval Deficits in any of these steps can cause amnesia. Amnesia, by definition, results from Memory Loss , not impairment of other functions (eg, attention, motivation, reasoning, language), which may cause similar symptoms. Amnesia can be classified as follows: Retrograde:Amnesia for eventsbeforethe causative event Anterograde:Inability to store new memoriesafterthe causative event Sense-specific:Amnesia for events processed by one sense—eg, visual memory Amnesia may be Transient (as occurs after brain trauma) Permanent, as occurs after a serious event such as Encephalitis , global ischemia, or cardiac arrest Progressive (as occurs with degenerative dementias, such as Alzheimer Disease ) Memory deficits more commonly involve facts (declarative memory) and, less commonly, skills (procedural memory). 