Transient global amnesia (TGA), is an anxiety-producing temporary loss of short-term memory. Typically, patients will not be able to remember events for the past few hours, and not be able to retain new information for more than a few minutes. Patients will suffer the effects of TGA for up to 24 hours, after which symptoms resolve. Worldwide, its incidence is approximately 2.9–10/100 000 cases per year. 
TGA is differentiated from stroke by the lack of tingling, peripheral limb involvement, speech impairment or ability to walk. It is differentiated from subarachnoid hemorrhage from the lack of headache. 
TGA does produce an inability to assimilate certain, generally current or recent, details while social skills and memories of distant past events or trivia is maintained.
-The attack was witnessed and reported as being a definite loss of recent memory (anterograde amnesia).
-There was an absence of clouding of consciousness.
-There were no focal neurological signs or deficits during or after the attack.
-There were no features of epilepsy, and the patient did not have any recent head injury or active epilepsy
-The attack resolved within 24 hours
The underlying cause of TGA is unclear. One current hypothesis is that TGA may be due to venous congestion of the brain , leading to ischemia of structures involved with memory, such as the hippocampus. This may be triggered by performing a Valsalva maneuver in the context of various precipitating events such as immersion in cold water, sexual activity, severe emotional stress and vigorous exertion.
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." 
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^ Magnus Harrison and Mark Williams
The diagnosis and management of transient global amnesia in the emergency department
Emerg Med J 2007; 24: 444-445. doi:10.1136/emj.2007.046565