|Classification and external resources| |ICD-9||294.0, 780.9,
780.93| Amnesia (from Greek Ἀμνησία "a" meaning "without",
"μνησία" memory) is a deficit in memory caused by brain damage,
disease, or psychological trauma. Amnesia can also be caused
temporarily by the use of various sedatives and hypnotic drugs.
Essentially, amnesia is loss of memory. The memory can be either
wholly or partially lost due to the extent of damage that was
caused. There are two main types of amnesia: retrograde amnesia
and anterograde amnesia. Retrograde amnesia is the inability to
retrieve information that was acquired before a particular date,
usually the date of an accident or operation. In some cases the
memory loss can extend back decades, while in others the person
may lose only a few months of memory. Anterograde amnesia is the
inability to transfer new information from the short-term store
into the long-term store. People with this type of amnesia
cannot remember things for long periods of time. These two types
are not mutua