Definition of Transient global amnesia

Transient global amnesia: A passing episode of short-term memory loss without other signs or symptoms of neurological impairment. In transient global amnesia (TGA) the individual does not lose consciousness but does lose the ability to form new lasting memories. Motor function is not affected. The individual may be disoriented to place and time, may recognize that something is wrong, and may become distressed at this realization. The average age of patients with TGA is 62 (range: 47-80) and the mean duration of the episode is 5.7 hours, with a range of 20 minutes to 20 hours.

The recommended criteria for the diagnosis of TGA are:

1. Attacks must be witnessed and information must be available from a capable observer.
   
2. Clear-cut anterograde amnesia must be present during the attack.
   
3. Clouding of consciousness and loss of personal identity must be absent and cognitive impairment must be limited to amnesia.
   
4. There must be no accompanying focal neurological symptoms or signs, and epileptic features must be absent.
   
5. Attacks must resolve within 24 hours.
   
6. Patients with a recent head injury or known active epilepsy are excluded.

Patients with many other clinical ­entities may present with amnesia and these may need to be ruled out before the diagnosis of TGA can be made. These conditions include alcoholic "blackouts," TIA (transient ischemic attack), temporal lobe epilepsy, brain tumor, drug reactions, and intracerebral or subarachnoid hemorrhage.