Transient global amnesia

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Classification according to ICD-10
G45.4 Transient global amnesia (amnesiac episode)
ICD-10 online (WHO version 2019)

The Transient Global Amnesia (TGA) or amnesic episode is a neurological disorder that frequently occurs in the elderly and a temporary disturbance of memory leads. It is considered harmless, but repeatedly leads to great concern among those affected and their relatives. The cause is a temporary dysfunction of the mediobasal temporal lobe (including both hippocampi ), the pathogenesis of which is not known.

Epidemiology

The annual new disease rate ( incidence ) is estimated at 3 / 100,000 inhabitants. Men and women are equally affected. The second half of life is clearly overrepresented, with transient global amnesia most common in the sixth decade of life.

Symptoms

There is a disturbance of memory that lasts up to 24 hours with a corresponding disorientation regarding time, situation and place ( anterograde amnesia ). The old memory remains largely intact; as far as the recent past is concerned, however, limitations are quite typical ( retrograde amnesia ) - hence “global” amnesia. Those affected make a perplexed impression. The constant repetition of the same questions, although they have already been answered several times, is very characteristic. The procedural memory , i.e. the ability to call up automated motor skills such as driving a car, is not disturbed. The symptoms appear abruptly and gradually and completely resolve after a few hours. It only leaves a memory gap for the time of the memory impairment .

Diagnosis

The diagnosis can usually be made clinically (without additional examinations) according to the criteria of Caplan (1985) and Hodges and Warlow (1990):

  • sudden and severe memory impairment
  • Preservation of procedural memory (e.g. continuation of complex activities such as playing the piano)
  • Duration 1 to 24 hours
  • no further abnormalities in the neurological examination
  • especially no impaired consciousness or disorientation towards the person
  • no previous trauma or epilepsy

The transient global amnesia must be differentiated, in particular, from memory disorders caused by:

treatment

Inpatient admission is always required if the diagnosis cannot be made clearly or if adequate care is not guaranteed at home. Ultimately, however, it is used to monitor the progress (waiting for improvement) and to carry out examinations ( EEG , MRT ) to rule out the above-mentioned serious diseases.

A rational therapy is not possible because the cause of the disease is not known. It does not seem necessary either, as there are no further consequences beyond the memory gap. Only the risk of a new transient global amnesia is slightly increased after a single episode.

Cause considerations

Diffusion-weighted MRI in TGA: punctiform diffusion disorders in the left hippocampus (right in the picture).

A transient circulatory disorder was primarily suspected. In the majority of patients, punctiform diffusion disorders in the lateral hippocampus can be detected in magnetic resonance imaging . However, this is contradicted by the fact that transient global amnesia, unlike other short-term ischemias of the head ( TIA , amaurosis fugax ), is not a risk factor for suffering a stroke .

Further, due to the association was to migraine a cortical spreading depression adopted as a common basis of both diseases. However, this could not be further substantiated in practice, and the age at the time it first appeared does not speak in favor of it.

Venous congestion of the blood flow from the head was also suspected. This is supported by studies on the venous valves of the jugular vein of TGA patients. However, there are no reports to date that such patients could induce transient global amnesia using a Valsalva maneuver . As with most diseases, the cause of which is not known, functional (psychogenic / dissociative) causes were also discussed, as with the rather longer-lasting and non-age-related dissociative amnesia . Ultimately, the cause is still not clear.

literature