Causes of Retrograde Amnesia
Stedmans medical dictionary (2001) defines retrograde amnesia as amnesia in reference to events that occurred before the trauma or disease that caused the condition (pg. 858). Therefore, retrograde amnesia affects the individuals memory for events that occurred prior to the trauma or disease. For example, frequently, individuals involved in automobile accidents do not remember what happened to cause the accident or even being in the accident.
Retrograde amnesia in its pure form is very rare, and would involve an injury or disease that affected either the hippocampus, which is an area of the brain responsible for long term memory, or the inferior aspects of the temporal lobe, which plays a role in the memory for both visual and auditory events. Retrograde amnesia is usually accompanied by anterograde amnesia, which is amnesia for events that follow the traumatic episode.
There are several reasons why an individual might develop retrograde amnesia. Of all of these, the most common cause would be head trauma, which includes falling, car accidents, sports injuries (i.e., boxing and football), or in general, receiving a blow to the head. During this type of injury, the individual sustains what is called both coup and contrecoup injury. The coup injury consists of the brain area directly involved in the impact, while contrecoup damage involves injury to the area opposite that at which the blow occurred. This shifting of the brain in the skull results in a great deal of shearing, in which axons (nerve cells) break, along with edema (swelling), which compresses the brain in the skull. Both of these factors result in further brain damage.
Another cause of retrograde amnesia would include anoxia, which is a deprivation of oxygen to the brain. Without much needed oxygen, brain cells begin to die and the result is gross (overall) damage to the brain. An example of an anoxic event would include drowning. Similar in nature, an ischemic event may cause retrograde amnesia. An example would include a stroke. However, the stroke should affect either the hippocampus or the inferior aspect of the temporal lobe in order to result in a retrograde amnesia.
Finally, diseases, such as epilepsy and encephalitis, may result in this type of amnesia. It should be noted that the epilepsy must be severe. Also, Korsakoff syndrome may cause retrograde amnesia. Korsakoff syndrome is an amnestic syndrome due to alcohol and is characterized by confusion and impaired memory. This is seen in individuals with alcohol dependence and poor nutrition.