Facts & Theories Regarding Transient Global Amnesia (TGA)
Facts
Theories
1. Transient Global Amnesia (TGA) is a syndrome of temporary disruption of short-term memory accompanied by repetitive questioning that resolves itself in usually less than 24 hours.
2. While the etiology (the cause, set of causes, or manner of causation of a disease or condition) remains unknown, TGA most commonly presents in 60 to 65-year-old females and males at a close to 50-50 split.
3. The incidence rate has been estimated at 23.5 to 32 per 100,000 per year.
4. The annual recurrence rate is approximately 2.5 to just over 5.0%
5. The clinical symptoms of TGA imply that the site of neurologic involvement would be the medial temporal lobe and hippocampus. This area of the brain is involved in the formation and retrieval of new episodic memories.
6. Mayo Clinic Overview:
“Transient global amnesia is a sudden, temporary episode of memory loss that can't be attributed to a more common neurological condition, such as epilepsy or stroke. During an episode of transient global amnesia, your recall of recent events simply vanishes, so you can't remember where you are or how you got there. In addition, you may not remember anything about what's happening in the here and now. Consequently, you may keep repeating the same questions because you don't remember the answers you've just been given. You may also draw a blank when asked to remember things that happened a day, a month or even a year ago. The condition most often affects people in middle or older age. With transient global amnesia, you do remember who you are, and you recognize the people you know well. Episodes of transient global amnesia always improve gradually over a few hours. During recovery, you may slowly begin to remember events and circumstances. Transient global amnesia isn't serious, but it can still be frightening.” Mayo Clinic Website https://www.mayoclinic.org/diseases-conditions/transient-global-amnesia/symptoms-causes/syc-20378531
1. Arterial ischemia has been proposed as one mechanism as transient ischemic attacks via arterial thrombo embolism and TGA share certain features such as duration of less than 24 hours and occurrence in older patients.
2. A venous congestion theory has been proposed in which Valsalva maneuvering impedes venous return via the superior vena cava, thus allowing transient retrograde transmission of elevated venous pressure to the cerebral venous system which may result in venous ischemia of the mesial temporal lobes.
3. A migrainous etiology has also been proposed in which TGA may be similar to an aura via cerebral spreading depression (a self-propagating wave of neuronal and glial depolarization) perhaps triggered by hippocampal glutamate release.
4. Epileptiform etiologies have also been proposed as a cause of TGA, given the transient amnesia may manifest some seizures.
5. Psychogenic causes have also been proposed based on findings that subgroups of TGA patients have certain phobic and other personality traits such as anxiety and depression.
6. A multi-factorial disorder is also plausible. There are certain precipitating triggers that have been identified, including alcohol use, severe nightmares, sexual activity, emotional distress, intense pain or cold, high altitude, myocardial ischemia, strenuous physical activity, and/or Valsalva maneuvers.
