• The main sign of TGA is being temporarily unable to form new memories. This is called prominent anterograde amnesia. During the episode of TGA, the person will seem disoriented in time and often ask questions about the date or their environment over and over again. This may be described as the person sounding like a "broken record."
• During the TGA episode, the person may forget memories from the recent past (retrograde amnesia). The period of memory loss varies and may extend back hours to days or weeks, but only in rare instances, years.
• Other cognitive functions (ability to think) are not affected. In other words, even during the TGA episode, the person will know who they are and will be able to recognize and name familiar objects and people. The person is able to perform normal complex daily tasks such as driving or cooking.
• No other neurological problems are noticed during an exam. For example, reflexes, balance and coordination are normal.
• The TGA episode lasts between 1 and 10 hours (6 hours is the average). When the episode is over, the person will be able to make new memories again, but there will be no memories from the time during the episode.
• Within 24 hours of the end of the TGA episode, any memories from the past lost during the episode will completely return. This does not include the time during the episode when no new memories could be made. In rare cases, some people may not remember an additional short period of time just before the TGA episode.
• Other less common symptoms include headache, nausea, dizziness, anxiety, and feelings of tingling and numbness in hands, feet, arms or legs.

There is currently no consensus on an underlying cause of transient global amnesia (TGA). Possible mechanisms that have been proposed include:

• A vascular etiology, such as venous flow abnormalities
• Hypoxia (deficiency of oxygen supply) and/or ischemia (deficiency of blood supply)
• A relation to migraine (some studies have shown that history of migraine is associated with TGA)
• Epilepsy
• Psychological factors

However, none of these theories clearly and consistently explain the features of TGA. Because no one theory appears to apply to all people with TGA, some speculate that TGA may have multiple different causes.

Events that reportedly may trigger an episode of TGA include:

• Sudden immersion in cold or hot water
• Physical exertion
• Emotional distress or psychological stress
• Pain
• Medical procedures
• Head trauma
• Sexual intercourse
• A Valsalva maneuver

There is a distinct form of TGA that may occur following excessive alcohol consumption, large sedative doses of barbiturates, the use of several illicit drugs, or sometimes, relatively small doses of benzodiazepines.

• Sudden immersion in cold or hot water
• Strenuous physical activity
• Sexual intercourse
• Medical procedures, such as angiography or endoscopy
• Mild head trauma
• Acute emotional distress (e.g., from bad news, conflict or being overworked)
• Exposure to high altitudes