Post-traumatic amnesia: symptoms, causes and features

After a severe blow to the head, this brain alteration that affects memory may appear.

Post-traumatic amnesia or post-traumatic amnesic syndrome occurs frequently in subjects who have suffered head injuries and can persist for years, seriously affecting the memory of events. Let's see what are its 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 functioning after consciousness has been regained.. Current research defines post-traumatic amnesia as a persistent, stable and global memory disturbance due to an organic brain disorder, in the absence of other cognitive deficits.

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

These memory deficits are mainly due to focal lesions in the hippocampus (a structure closely linked to memory). (a structure closely linked to memory and special localization) and contiguous structures, as well as other diffuse brain damage.

Characteristics of this syndrome

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

This mnesic syndrome is composed of several factors such as loss of consciousness resulting from the injury or trauma, retrograde amnesia (inability to remember events occurring before the injury) and, sometimes, anterograde amnesia. Parkin and Leng defined the following features of posttraumatic amnesia:

• There is no short-term memory deficit (assessed by tasks such as digit span).
• Semantic memory, responsible for encoding, storing and retrieving learned information, is not affected.
• Permanent inability to store new information after the lesion (assessed by recall and recognition tests).
• In some patients, inability to retrieve information stored in long-term memory prior to the lesion.
• Procedural memory (responsible for recall of 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 impairment?

Blows and trauma to the head and skull are the best known causes when referring to amnesia. causes of post-traumatic amnesia. However, there are other factors -some of them avoidable- to be taken into account in order to know what can cause this type of syndrome.

1. Stroke

A stroke happens when the flow of Blood to the brain stops and it can no longer receive oxygen and nutrients. Neurons may eventually die, causing permanent functional and structural damage.

2. Encephalitis

Encephalitis or inflammation of the brain can originate as a result of a viral infection (e.g. 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 oxygen, can be causative factors in a disease.may be causative factors in post-traumatic amnesia. This lack of oxygen may 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. Severe thiamine deficiency can lead to brain damage and the development of Wernic syndrome. the onset of Wernicke-Korsakoff syndrome.a brain disease that causes lesions in 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 usually accompanied by strong temporal and spatial disorientation, attentional deficits (mainly in sustained and focused attention), retrograde and anterograde amnesia, confabulation, agitation and disinhibited behavior.

During the course of the syndrome patients feel confused, disoriented and have great difficulty processing information coming from the environment.. Depending on the intensity of the injury, patients will remember with greater or lesser difficulty the events surrounding the accident or minutes before.

In terms of language, subjects suffering from post-traumatic amnesia often present incoherent speech and their perception of the environment and novel stimuli is distorted, leading to exacerbated confusion and fear.

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

Other memory deficits

In addition to post-traumatic amnesia, there are other types of memory syndromes in which different types of memory in various brain areas are affected. The most common ones are presented below:

1. Temporal amnesic syndrome

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

2. Diencephalic amnestic syndrome

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

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

3. Frontal amnesic syndrome

Amnesias due to lesion in the frontal cortex do not produce an overall loss of memoryThis is because this area of the brain is responsible for strategic processes of retrieval, monitoring and verification of information. On the other hand, patients' ability to search for and select relevant information for each situation and context is impaired.

4. Semantic dementia

This type of amnestic syndrome syndrome is characterized by a significant impairment of the retrograde declarative memory (responsible for storing (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.

Bibliographical references:

• Fernández-Ballesteros, R. (2005). Introduction to Psychological Assessment I and II. Ed. Pirámide. Madrid.
• Kolb, B. & Wishaw, I.Q. (2006) Human Neuropsychology (5th Ed.). Editorial Médica Panaméricana: Buenos Aires.