Transient Global Amnesia (TGA) is the complete inability to formulate new memory. Suddenly, new memories no longer register in the victim's mind, a condition known as anterograde amnesia. Any sensory input during this time will be preserved briefly, if at all, disappearing completely and forever within seconds, as though it never happened.
By Duane Graveline, M.D., M.P.H.
The onset of transient global amnesia is abrupt, without the slightest warning to the patient that a central nervous system catastrophe is about to strike. Although consistently aware of their own identities, patients are often perplexed as to their surroundings and the identity of those around them.
Individuals with transient global amnesia are surprisingly competent in many respects. Anecdotal reporting from observers indicates that routine tasks such as walking or jogging, riding a bicycle or even driving a car appear to be done as usual.
Although they can speak in a disarmingly normal manner, victims of TGA cannot communicate for they cannot remember words just spoken. Attempts at communication are often pathetically farcical as their responses to questions are usually totally irrelevant although earnestly delivered in a normal speech manner.
Characteristically, these TGA victims repetitively question those present about where they are and what is happening but are unable to remember any explanation. To the consternation and ultimate frustration of doctors, nurses and well-meaning companions, they ask the same question, over and over again, sometimes for hours.
In most of these cases disorientation is profound. Language and social skills are preserved and the ability to focus attention appears normal but, alas, despite the victim's desperate and almost pathetic desire to learn what is happening, nothing seems to register.
Fortunately, most are mercifully spared awareness of their memory impairment and preserve a remarkably calm demeanor, cooperating fully with their examiners. Many, but not all, of these people will have an extensive retrograde component to their amnesia extending back many years in their lives. Gone are memories of friends and relatives, marriages and deaths, positions held and occupations learned.
Since TGA was first identified in 1956, approximately 1000 cases had accumulated in the medical literature until the advent of the statin drugs. Now ER doctors find themselves turning to their sometimes dusty, neurology books to identify this formerly rare condition, now seen in some statin users.
During the pre-statin period a number of apparent precipitory factors had been reported. Moderate to severe physical exertion often precedes an episode; activities such as heavy digging, felling a tree, and laying concrete. Unusual emotional stresses such as newly reported cancer, a death in the family, news of a severe accident, and violent family arguments can trigger these reactions.
Swimming in cold water is occasionally a factor, and some individuals appear to recognize sexual intercourse as a frequent, and even consistent, trigger. Occasionally, transient global amnesia episodes have occurred after routine medical procedures such as venipuncture, minor surgery or application of the Valsalva maneuver, a "grunting" expiration test commonly used to determine cardiovascular responsiveness.
Another medical procedure identified as a trigger agent for a growing number of transient global amnesia cases is cerebral angiography. However, none of these seemingly diverse trigger agents have provided useful information as to the precise cause of transient global amnesia.
Millions of patients are now taking this class of drug and are at significant risk for cognitive side effects. Transient global amnesia is just the tip of the iceberg. For every reported case of TGA there are hundreds of reports of impaired memory, disorientation and confusion among an older group of patients that rarely get mentioned. All too frequently, this group is willing to accept old age, "senior moments" or incipient senility as the cause, particularly when their physicians are also ignorant about this side effect of the statin drugs.
Additionally, TGA is vastly under-reported because of the frequent lack of an observer. A patient recovering from such an attack has no recall of the event. And brief episodes of transient global amnesia, measured in minutes rather than hours, frequently offer no clue, even with an observer. Dozens of such attacks may occur undetected.
Attacks of transient global amnesia are thought to be largely benign in nature with cognitive impairment generally resolving after a few hours. Usually the resulting memory gap is only for the duration of the attack but, for some, the gap extends back hours, weeks and even years before the attack resulting in a retrograde memory loss as well. Any of life's experiences and training during this retrograde gap are now lost to the victim.
Characteristically, the neurological examination is completely normal except for the amnesia and, after periods of usually less than twelve hours, recovery spontaneously occurs. This restoration of memory takes place quite rapidly, usually within fifteen to thirty minutes after improvement begins until recovery is complete. During this time patients become progressively aware of their emergence from amnesia and, to the profound relief of those around them, their repetitive questioning finally ceases.
Duane Graveline MD MPH
Former USAF Flight Surgeon
Former NASA Astronaut
Retired Family Doctor
Updated October 2011