What is Amnesia?
Amnesia or Loss of Memory is quite a complex concept and is a symptom rather than a disease in its own right as it has many causes and varies considerably between individual cases. It is divided roughly into anterograde amnesia and retrograde amnesia. Patients may have one or the other or a combination of the two depending on the cause and location of the brain damage. The brain damage itself can be caused by trauma such as a blow to the head, a brain bleed, brain swelling, stroke, a tumour or a disease such as viral encephalitis or a dementia such as Alzheimer’s disease.
Anterograde Amnesia is the inability to make new memories after a brain trauma or due to illness. It is often as a result of damage to the hippocampus. The extent and duration of this form of disorder depends on the severity of the brain damage and whether there is sufficient of the hippocampus to recover and eventually start encoding new memories. Damage to other parts of the brain involved in the creation of new memories can also cause this form of amnesia, particularly when the chemical balance of the brain is disturbed. When the chemical balance is restored the ability to make new memories may return.
Retrograde Amnesia is the inability to remember the past and once again can be as a result of brain trauma or illness. Often very early memories can be remembered quite clearly as they are the most firmly embedded whereas more recent ones prior to the incident that caused the amnesia may be lost. The physical part of the brain in which the memories are stored may be damaged or affected by illness in which case the memories may no longer be there to recall. Amnesia may also be caused by problems with the brain’s retrieval system in which case the memories are physically still there but the ability to retrieve them has been lost.
In Alzheimer’s disease and other forms of dementia it is usually short term memory that is affected first whereas long term memory, particularly procedural and episodic or autobiographical memory may be the last to go. The short term memory problems in this case are believed to be caused by chemical imbalances, tau tangles and the build-up of amyloid protein in the brain, preventing synapses from firing properly and neurons from being able to form new memories.
Amnesia is more than just forgetting where you put your keys, it is a very serious condition and can have a devastating impact on everyday life, particularly if in the case of anterograde amnesia, the inability to create new short-term memories. This is not something that can be ignored, particularly if it occurs suddenly or is connected with any other event or symptoms such as a blow to the head, high fever, pain in the neck, visual disturbances and so on.