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Transient global amnesia

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Abstract

VOL: 100, ISSUE: 27, PAGE NO: 33

What is it?

- Transient global amnesia (TGA) is a temporary and isolated disorder of the memory.

- An episode of this disorder consists of a loss of recent and new memories.

- An episode of TGA usually occurs spontaneously.

- The syndrome is largely benign in nature due to the fact that the episode is temporary.

- The patient is usually otherwise healthy and middle aged or older.

- An attack may last several hours.

History

- TGA was first described in 1956 by Morris Bender.

- Since then, TGA has become a well-explained syndrome but its cause is still not totally understood.

- TGA affects memory function. 

Although many mechanisms have been proposed, no single cause can fully explain all the features of TGA.

- Some authors have stated that patients with TGA have age and risk factor profiles similar to those of patients who experience stroke or transient ischaemic attack (TIA).

Causes

Precipitating factors include:

- Sexual intercourse;

- Heavy physical exercise (usually swimming in cold water);

- There is a small correlation between TGA and patients who suffer from migraines, epileptic fits, and cerebrovascular disease;

- Physical or emotional stress;

- Driving a car.

Pathophysiology

- The precise pathophysiology of TGA is not clear.

- Blood flow to specific brain areas that involve memory including the thalamus and/or mesial temporal structures appears to be disrupted transiently during TGA.

Incidence

- Three people per 100,000 of the population per year are affected with TGA.

- The condition affects 50 per cent more men than women.

- Less than 25 per cent of patients experience repeated episodes. 

- Less than three per cent of patients experience three or more episodes.

- Permanent memory loss is rare.

Symptoms

A patient with TGA:

- Is acutely confused;

- Is neurologically intact except for absent memory (for example, remains alert, remembers identity, remembers past experiences); 

- Asks relevant questions repeatedly because she or he does not remember the answer;

- Is unable to recall the episode once she or he has recovered;

- Usually maintains her or his semantic memory (long-term memory responsible for retaining knowledge about the world, including the meaning of words and objects) and meta memory (the awareness of what one should know);

- Anterograde amnesia must be present.

Treatment

- There is no treatment.

- TGA is short-lived.

- Patients with recurrent episodes usually do not experience any increased morbidity. 

Differential diagnosis

- Toxin-induced memory loss tends to include inattention and an inability to sustain coherent thought.

- In complex partial seizures, repetitive questioning is not a feature.

- Psychogenic amnesia tends to occur at a younger age and the patient is more likely to have personality changes and not remember personal details. 

Website

Transient Global Amnesia (GP notes): www.gpnotebook.co.uk/cache/1557135375.htm

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