Synonyms
Memory loss, “blackout”
Definition
Amnesia is a mostly temporary disturbance of memory for temporal orientation or content memory. Amnesia is a symptom that can occur in a variety of triggering disorders or factors and must be distinguished from dementia, where the memory disorder progresses slowly and is persistent.
Causes
Many disturbing influences on the brain can lead to an impairment of consciousness and memory, which can be observed, for example, through the influence of poisons, in the form of alcohol, drugs (e.g. tranquilizers), but also drugs. Furthermore, violent influences of all kinds (mechanical, electrical) on the brain lead to memory gaps, which is also diagnostically groundbreaking in the case of concussion as the mildest form of craniocerebral trauma. Diseases of the brain, such as epilepsy, stroke or inflammations of various causes as well as migraine can also lead to amnesia.
Finally, there are psychiatric diseases such as personality disorders, dissociative disorders and hypnosis, which can also lead to a loss of consciousness or memory. If an injury to the brain occurs as a result of the use of force in an accident, this is known as a craniocerebral trauma. This can also be caused by a fall on the head.
Due to the duration of unconsciousness, different degrees of severity can be distinguished. The weakest form of craniocerebral trauma is a concussion. In this case the patient is unconscious only for a short time (up to a maximum of 10 minutes).
A typical symptom is retrograde amnesia. The patient cannot remember the exact course of the accident. The accompanying symptoms are nausea and vomiting.
A memory loss for future events, called anterograde amnesia, is unlikely to occur in mild brain injuries. This form of amnesia can occur in more serious brain injuries when nerve cells are compressed by bleeding or oedema. If the accident has caused extensive irreversible damage to the nerve cells, the amnesia will persist.
Memory training can help to activate other areas of the brain to compensate for the loss of function. Amnesia can also be triggered by stress. On the one hand it can lead to dissociative amnesia.
This form of amnesia leads to selective memory gaps in relation to autobiographical memories. Experts understand dissociative amnesia as a kind of protective function of the psyche in order to avoid having to repeatedly deal with stressful events. But stress also plays an important role as a trigger in transient global amnesia.
It occurs particularly frequently when physical and psychological stress situations have preceded it. It is as if the brain is taking a short break. After 24 hours at the latest, the memory gap closes again and the patient’s ability to remember is no longer restricted.
After excessive alcohol consumption, a so-called blackout can occur after waking up. The affected person has a memory gap of up to several hours. This is a temporary amnesia, i.e. the memory recovers over the course of time.
It is very different from which amount of alcohol an amnesia is triggered. Chronic alcohol consumption can lead to the development of Korsakow syndrome due to a vitamin B1 deficiency. The main symptom of this disease is amnesia.
This sometimes exists in a global form, i.e. both experienced events and new content can no longer be retrieved. Often, however, old memory contents are well remembered. However, patients cannot remember newly experienced events.
Unconsciously, the patients fill these memory gaps with fantasy content. This is called confabulation in medical terminology and is a typical symptom of the Korsakow syndrome. A loss of memory or memory disorders after a stroke are common.
The type and extent depend on which area of the brain is affected and how severely it is damaged. In patients with a stroke in the left hemisphere of the brain, there are often problems with semantic memory. Those affected cannot remember facts well.
The memory of personal experiences is not disturbed. This is more common after a stroke in the right hemisphere of the brain; this is where episodic memory is localised. Often these disturbances are only temporary or at least partially disappear.
However, if the stroke has caused nerve cells to die in large areas, the amnesia is permanent. Epileptic seizures are very often accompanied by amnesia. The type and extent of amnesia can vary greatly from patient to patient.
In most cases, the amnesia after an epileptic seizure is only temporary and quickly recedes. In a rare form of temporal lobe epilepsy, amnesia is the only symptom. Here, recurrent memory disorders occur without any other accompanying symptoms.
The epileptogenic focus is suspected in the hippocampus. Here, the EEG can also reveal abnormalities. The most important differential diagnosis is transient global amnesia.
After surgical interventions, memory disorders are often noticed in patients postoperatively. These are of short duration and usually refer to events immediately before or after the operation. This is usually also related to the drugs that are administered to the patient to induce anaesthesia.
Therefore, the memory gap is even desired, after all, many patients experience these events as partly traumatic. After neurosurgical operations on the skull, amnesia can also extend beyond the immediate postoperative phase. In older patients, too, it is often observed that memory disorders persist for a long time after the operation.
It is unclear whether this can be seen as a harbinger for the development of dementia. Amnesia after waking up often exists in the context of a drowsiness. In this state, the affected person is disoriented in terms of time and place after waking up.
This is also accompanied by a psychomotor slowdown. Usually this state lasts for a maximum of 15 minutes. The memory of this time is fragmentary. Characteristic for this sleep disorder is that it occurs from deep sleep. It can be provoked by waking up, but also occurs during spontaneous awakening.
