Tuesday, September 1, 2009
Mayoclinic.com defines transient global amnesia (TGA) as "a sudden, temporary episode of memory loss that can't be attributed to a more common neurological condition." MedicineNet.com calls it "a passing episode of short-term memory loss without other signs or symptoms of neurological impairment." The condition is rare.
TGA is often diagnosed because of what's not happening rather than what is. The amnesia is obvious, but it's the only cognitive symptom. The diagnosis is made by eliminating other possibilities, such as stroke, through tests such as EEGs (electroencephalograms) to check the brain's electrical activity, and CT (computerized tomography) scans, which look for brain abnormalities such as broken blood vessels.
People who experience TGA still know who they are and recognize people they know. There is no loss of consciousness, and there are no lasting effects.
Oxford Journals, a publisher of scientific research, says the first reports of TGA appear in 1956. A report from the 1980s, when several major studies of the condition were conducted, determined there may be 5.2 cases per 100,000 people annually. That rises to 23.5 cases per 100,000 for people older than 50. Second episodes are very uncommon.
Research shows that emotional stress or anxiety might trigger TGA in women, and physical stress appears to be a factor among men, but the underlying cause isn't known. TGA appears to affect people mostly from their mid-50s to mid-70s. Migraine might be a factor among younger people. Sex, high cholesterol and high blood pressure don't seem to play any role. Compression of the large veins that leave the brain may be involved.
No treatment is needed, and there's no proven way to prevent TGA. Because the symptoms are similar to those of stroke, medical personnel advise calling an ambulance immediately.
-- Carol and Dave Ochs