Amnesic syndrome: causes, symptoms, and main types.

A collection of symptoms of memory loss caused by brain damage.

Lesions in the medial temporal lobe cause deficits in anterograde memory, and frequently also in retrograde memory.

In this article we will analyze what amnestic syndrome is and what are its main causes, including the most common and characteristic one: Wernicke-Korsakoff syndrome, which is due to malnutrition and alcohol abuse.

What is amnestic syndrome?

The concept of "amnestic syndrome" is relatively generic in nature.. It is used to refer to any permanent memory impairment that occurs as a result of damage to the brain, so it can include disorders due to many different causes; however, Wernicke-Korsakoff syndrome is the most representative.

The term "amnestic syndrome" is generally used to refer to disorders that specifically affect memory, without other cognitive deficits (e.g. in intelligence or language) being present. If they are, memory problems are usually of much greater clinical significance than the rest.

Consequently, the causes of amnestic syndrome the causes of amnestic syndrome tend to consist of focal lesions of the medial areas of the temporal lobe, specifically in the structures of the temporal system.The causes of amnesic syndrome tend to consist of focal lesions in the medial areas of the temporal lobe, specifically in the limbic system structures involved in the consolidation and retrieval of memories, such as the hippocampus and amygdala, which are fundamental in spatial and emotional memory respectively.

Types of amnesia: retrograde and anterograde.

This type of damage causes the affected person to have severe problems in learning new information; this phenomenon is known as anterograde amnesia, and is sometimes, but not necessarily, accompanied by retrograde amnesia, consisting of the forgetting of memories that were encoded before the brain lesion.

At the clinical level, patients with amnesic syndrome may show apparently normal functioning, since their working memory is not affected, nor is their ability to perform new procedural learning. However, deficits in declarative memory deficits in declarative memory interfere greatly in the lives of these individuals..

Retrograde amnesia is generally more evident for recent memories than for distant ones, although its severity depends on the lesion. As for anterograde amnesia, it is now known that it is usually not as extreme as it was thought years ago, since the maintenance of other memory functions makes it possible to compensate for declarative deficits.

Main causes of this disorder

Any factor likely to damage the medial temporal regions of the brain has the potential to cause an amnestic syndrome. The most common causes are Wernicke-Korsakoff syndrome, which is associated with excessive alcohol consumption, herpetic encephalitis and anoxia, as well as strokes, hemorrhages and brain tumors.

Retrograde amnesia is also one of the most characteristic side effects of electroconvulsive therapy, which is occasionally applied in cases of major depression and bipolar disorder, among other psychological disorders. However, many authors would not consider these effects a true amnestic syndrome because of their transience.

1. Wernicke-Korsakoff's syndrome

Wernicke-Korsakoff syndrome is due to deficiencies of vitamin B1, which is also called thiamine.. The most frequent cause is malnutrition, especially when it is related to the abuse of alcoholdurante a long period of time. This disease consists of two phases: Wernicke's encephalopathy and Korsakoff's syndrome.

During the acute phase, symptoms and signs include attention problems, confusion, temporal, spatial and personal disorientation, apathy, neuropathic pain, ataxia (general lack of motor coordination), nystagmus (involuntary pupillary movements) and ophthalmoplegia (paralysis of the eye muscles).

The term "Korsakoff's syndrome" refers to the chronic phase of this process, in which severe alterations appear in both anterograde and retrograde memory; in the latter case, forgetfulness usually affects memories encoded up to two decades before the onset of Wernicke's encephalopathy.

2. Cerebrovascular accidents

Strokes and hemorrhages in the brain are two very common causes of amnestic syndrome, particularly when they occur in the anterior communicating artery, anterior cerebral artery or Heubner's artery. Involuntary fabrication or invention of memories, a characteristic sign of amnestic syndrome, is very common in these cases.is very common in these cases.

Another similar phenomenon that is also associated with amnesia is cerebral anoxia, which consists of the interruption of oxygen supply to this organ as a consequence of cardiac arrest; this can lead to the destruction of cells in the hippocampus and other regions of the temporal lobe, which explains the appearance of memory problems.

3. Tumors in the ventricles

The development of tumors in areas close to the limbic system frequently causes amnestic syndrome.. A particularly noteworthy case is that of tumors in the third ventricle, which often damage the fornix, the main connection between the thalamus and the structures involved in memory.

4. Herpetic encephalitis

Herpetic encephalitis is a disease of the central nervous system caused by infection with the herpes simplex virus.The disease can cause permanent symptoms such as amnesia, confusion and epileptic seizures due to lesions in the hippocampus, amygdala, uncus and other areas of the limbic system.