Transient Global Amnesia
Overview
Transient global amnesia is a sudden, temporary episode of memory loss that can't be attributed to a more common neurological condition, such as epilepsy, transient ischemic attack, stroke or head injury. During an episode of transient global amnesia, your recall of recent events simply vanishes, so you can't remember where you are or how you got there. You may also draw a blank when asked to remember things that happened a day, a month or even a year ago. You do remember who you are, and you recognize family members and others you have known for a long time, but that knowledge doesn't make your memory loss any less disturbing. Transient global amnesia would be even more distressing if it recurred more often or lasted longer than it does. The condition is rare to start with, and among the few who do have one episode, a second episode is uncommon. Also, episodes of transient global amnesia last only six hours, on average — although an episode of any length is frightening to witness or experience. When an episode of transient global amnesia is over, you remember nothing that happened while your memory was impaired, and you might not recall the hours beforehand. Otherwise, though, your memory is fine.
Symptoms
Transient global amnesia is identified by its main symptom, which is the inability to recall the recent past. Once that symptom is confirmed, ruling out other possible causes of amnesia is important. Diagnostic criteria The criteria for a diagnosis of transient global amnesia are: Sudden onset of memory loss, verified by a witness Retention of personal identity despite memory loss Normal cognition (ability to recognize and name familiar objects and follow simple directions, for example) Absence of signs indicating damage to a particular area of the brain (limb paralysis, involuntary movement or impaired word recognition, for example) Duration of no more than 24 hours Gradual return of memory No evidence of seizures during the period of amnesia No history of active epilepsy or recent head injury Additional signs and symptoms These signs and symptoms sometimes accompany the chief symptom, memory loss. Headache Nausea Vomiting Dizziness Chills or flushing Fear of dying Pins-and-needles sensation Cold hands and feet Powerful expression of emotion Trembling Sweating Chest or neck pain Visual disturbance Racing heartbeat
Causes
About half of all transient global amnesia episodes start just after a physically or emotionally stressful incident. Among the triggering events commonly reported are: Sudden immersion in cold or hot water Strenuous physical activity Sexual intercourse Medical procedures, such as angiography or endoscopy Acute emotional distress, as might be provoked by bad news, conflict or overwork The underlying cause of transient global amnesia is unknown. The incidence of migraine may be higher than can be explained by chance among those affected by transient global amnesia, suggesting that similar processes may be involved in both conditions. Compression of the large veins that empty oxygen-depleted blood from the brain and arms back into the heart may play a role as well. Many of the physical stresses experienced just before an episode of transient global amnesia result in compression of these veins.
Diagnosis
Diagnosis of transient global amnesia rests on excluding more serious conditions — stroke, seizure or head injury, for example — that can cause the same type of memory loss. The process begins with a neurological exam, checking your reflexes, muscle tone, muscle strength, sensory function, gait, posture, coordination and balance. Your doctor may also ask questions to test your thinking, judgment and memory. By checking your knowledge of general information — such as the name of the current president — and assessing your ability to recall a random list of words, the doctor can determine the extent of memory loss.
Prognosis
The prognosis of TGA is very good. It does not affect mortality and has a small recurrence rate. "The most important part of management after diagnosis is looking after the psychological needs of the patient and his or her relatives. Seeing a once competent and healthy partner, sibling or parent become incapable of remembering what was said only a minute ago is very distressing, and hence it is often the relatives who will require reassurance."
Treatment
No treatment is needed for transient global amnesia. It's self-limited and has no confirmed after-effects.