What is Transient Global Amnesia?
Amnesia is usually associated with memory loss that is sudden but permanent. BUT there is a form of amnesia that is comes on suddenly then goes and usually does not return.
Transient Global Amnesia is the term that is used to describe this kind of amnesia.
While I have seen amnesia many times, I have seen on case of (TGA) in my many years of practice.
A number of years ago a physician came to my office accompanied by his wife with a complaint of sudden onset memory loss for events that occurred for more than 12 hours.
As best as could be reconstructed, he functioned well treating his patients without error and observed all the while by his office staff.
What they did not know at the time was that this doctor did not remember the day's events.
As strange as that may seem, when he was interviewed, he could not tell me what he had done or which patients he had seen on that day. In fact, his anxiety about this circumstance as one might imagine was extremely high.
Prior to coming to my office he had seen his own personal physician who gave him a routine examination which was within normal limits. He was then referred to a neurologist who ordered a CT scan of his head. It to was normal.
This is not an usual scenario with TGA. Transient forms of amnesia have often been seen in cases of epilepsy and blood vessel abnormalities within the brain.
In the case of epilepsy there is a subgroup of people with temporal lobe epilepsy who have striking periods of amnesia. The temporal lobe is located in the left and right sides of the brain in the area above the ears.
In the case of blood vessel abnormalities or vascular problems the irregular functioning can be a temporary blocking of blood flow in the areas of the brain that relate to memory processing.
Most research on this topic has indicated that the persons memory loss when assessed later on formal neuropsychological tests has resolved within weeks or certainly months.
Some studies have indicated that verbal long term memory or time estimation could have been more permanently affected.
However, research has shown that procedural learning, semantic memory and implicit memory are all intact during the TGA episode.
BUT TGA is usually viewed as a sudden memory loss episode which is temporary. On examination these people are not usually found to have a more common neurological condition, such as epilepsy or cerebral vascular accident (CVA)(ischemia) or stroke.
So what is the cause?
This remains a mystery. As noted above, most forms of transient amnesia are in fact identified as being caused by stroke or a seizure than by transient global amnesia.
Thus, the condition is really defined by the effect (the brief 6-24 hour amnesia) than an actual clear cut cause.
IMPORTANT: If you or someone you know has had an episode of TGA it is extremely important to seek immediate medical attention to rule out a stroke or epilepsy.
Remember: If the person experiencing memory loss is too confused to call an ambulance, call 911 yourself.
For more information on amnesia see consult these resources:
The Amnesias: A Clinical Textbook of Memory Disorders by Andrew C. Papanicolaou
Memory Disorders: Fugue State, Transient Epileptic Amnesia, Transient Global Amnesia, Anterograde Amnesia, Psychogenic Amnesia on Amazon