Post-traumatic amnesia: symptoms, causes and characteristics

Post-traumatic amnesia or post-traumatic amnesic syndrome it occurs frequently in subjects who have suffered head injuries and can persist for years, severely impairing the memory of events. Let's see what its features are.

• Related article: "The different types of amnesia (and their characteristics)"

Post-traumatic amnesia: definition

The term post-traumatic amnesia was first coined by the English neurologist Charles P. Symonds to refer to a general disturbance of brain function after consciousness has been restored. Current research defines post-traumatic amnesia as a persistent memory disturbance, stable and global, due to an organic brain disorder, in the absence of other types of deficits cognitive.

In post-traumatic amnesia there is a difficulty in recalling and acquiring new information; the subject is unable to keep a continuous record of his daily activities. This syndrome frequently occurs in moderate and severe traumatic brain injury (TBI), along with permanent memory deficits.

These memory deficits are mainly due to focal lesions in the hippocampus.

(structure closely linked to memory and special localization) and contiguous structures, as well as other diffuse brain damage.

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Characteristics of this syndrome

Post-traumatic amnesia is the result of the sum of various factors such as loss of consciousness caused by the injury, retrograde amnesia that ranges from a few minutes to years prior to the accident and anterograde amnesia ranging from a few hours to months following recovery from the awareness.

This memory syndrome is made up of various factors such as loss of consciousness as a result of injury or trauma, retrograde amnesia (inability to remember events that occurred before the injury) and sometimes amnesia anterograde. Parkin and Leng defined the following features of post-traumatic amnesia:

• There is no short-term memory deficit (assessed by tasks such as digit span).
• Semantic memory, in charge of encoding, storing and retrieving learned information, is not affected.
• Permanent inability to store new information after injury (assessed by recall and recognition tests).
• In some patients, inability to retrieve information stored in long-term memory prior to injury.
• Procedural memory (responsible for remembering motor and executive skills) is not affected.
• Motor skills are preserved and the subject is able to form new memories in procedural memory.

What can cause this memory disturbance?

Blows and trauma to the head and skull are the best known causes when we refer to post-traumatic amnesia. However, there are other factors -some avoidable- to take into account to find out what can cause a syndrome of this type.

1. stroke

A stroke happens when blood flow to the brain stops and it can no longer receive oxygen and nutrients. Neurons can die, generating permanent functional and structural damage.

2. Encephalitis

Encephalitis, or inflammation of the brain, can result from a viral infection (for example, the herpes simplex virus) or as an autoimmune reaction to cancer.

3. Hypoxia or anoxia

Hypoxia, when there is a lack of oxygen, and anoxia, when there is a total absence of it, may be causal factors in post-traumatic amnesia. This lack of oxygen can be due to a heart attack, respiratory distress, or carbon monoxide poisoning, for example.

4. Alcohol abuse

Long-term alcohol abuse can lead to thiamine (vitamin B1) deficiency. A severe deficiency of this vitamin can lead to brain damage and the appearance of Wernicke-Korsakoff syndrome, a brain disease that causes damage to the thalamus and hypothalamus, resulting in irreversible damage to cognitive functions such as memory.

5. Degenerative diseases, tumors and other pathologies

Degenerative brain diseases, tumors and other pathologies such as cancer can cause memory syndromes depending on the areas of the brain affected.

Symptoms

Post-traumatic amnesia is generally accompanied by strong temporal and spatial disorientation, attention deficits (mainly in sustained and focused attention), retrograde amnesia and anterograde, collusion, agitation and disinhibited behavior.

Over the course of the syndrome, patients feel confused, disoriented and have great difficulty processing information from the environment. Depending on the intensity of the injury, patients will have more or less difficulty remembering the events that occurred around the accident or minutes before.

With regard to language, subjects suffering from post-traumatic amnesia often present incoherent speech and their perception of the environment and of new stimuli is distorted, leading to an exacerbation of confusion and fear.

It is also common for patients to be aggressive (physically or verbally) and restless. In addition, people with post-traumatic amnestic syndrome may present hallucinations.

Other memory deficits

In addition to post-traumatic amnesia, there are other types of memory syndromes in which different types of memory are affected in different brain areas. Below are the most common:

1. temporary amnesic syndrome

In the amnesias in which the medial temporal lobe is affected, the patient usually presents an anterograde episodic and semantic amnesia (affecting both general and personal and autobiographical information) and retrograde amnesia. However, short-term and procedural memory is preserved.

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2. Diencephalic amnesic syndrome

In diencephalic amnesias, patients present with retrograde amnesia and anterograde amnesia (both semantic and episodic) that is not always explained by an inability to store information but can be related, in part, to a memory disorder, an element that distinguishes them from amnesia temporary.

On the other hand, in this syndrome there is also a deficit in metamemory (ability to assess their own memory capacity)

3. frontal amnesic syndrome

Amnesias due to damage to the frontal cortex do not cause a global memory leak, since this area of ​​the brain is in charge of strategic processes of recovery, monitoring and verification of information. On the other hand, patients do see their ability to search for and select relevant information for each situation and context diminished.

4. semantic insanity

This type of amnestic syndrome It presents with a significant affectation of declarative retrograde memory (responsible for storing memories and events of our life that can be expressed explicitly). However, non-declarative memory, language grammar, and other cognitive functions are preserved.

Bibliographic references:

• Fernndez-Ballesteros, R. (2005). Introduction to Psychological Assessment I and II. Ed. Pyramid. Madrid.
• Kolb, B. & Wishaw, I.Q. (2006) Human Neuropsychology (5th Ed.). Pan-American Medical Editorial: Buenos Aires.