Transient global amnesia: A retrospective study of 25 patients

Background. Transient global amnesia (TGA) is a syndrome characterized by an abrupt onset of severe anterograde amnesia and variable retrograde amnesia, usually accompanied by repetitive query during the attack. Its etiology is unknown. Methods. We retrospectively studied patients who were admitted to National Cheng Kung University Hospital during, or just after, their first transient amnesic episode between July, 1988, and December, 1997. We examined the details of the attacks, including time of onset, duration, activities upon onset, potential precipitating factors, behavior during attack, and accompanying neurologic signs or symptoms. We also inquired about past medical history, current status and recurrence. Results. Twenty-five patients, 11 men and 14 women met the criteria for TGA. Their ages ranged from 27 to 77 years (mean, 60 years). The length of an attack ranged from one to 11.5 hours (mean, 6.3 hours). Nineteen attacks occurred in the morning and 10 had precipitating factors. The significant past history included hypertension, cardiovascular disease, migraine headache and thyroid disorders. None of the patients had a family history of TGA. Investigation revealed abnormal cerebral computerized tomographic (CT) scans or magnetic resonance images in three patients (12%), abnormal cerebral single photon emission CT (SPECT) in six (86%) of seven performed within the first eight days, and abnormal electroencephalography (EEG) in five patients (24%). The left temporal region was the most common site of dysfunction shown by EEG and cerebral SPECT. Three (12%) patients experienced a recurrent attack. Conclusions. Our patients had a higher rate of thyroid disorders, and most had their amnesia attacks in the morning. As compared with previously published studies, the results showed no differences with respect to age, duration of behaviour during attack, EEG, CT, family history and recurrence rate. The exact duration of an attack is sometimes difficult to estimate. Moreover, the increasing case numbers over the years indicates the importance of the need for better education of medical residents regarding TGA.