Amnesia can be classified as follows: Retrograde: Amnesia for events before the causative event Anterograde: Inability to store new memories after the causative event Sense-specific: Amnesia for events processed by one sense—eg, visual memory Amnesia may be Transient (as occurs after brain trauma) Fixed (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).