Allokiria: symptoms, causes and treatment.

A neurological disorder related to the hemispheres of the brain.

Allokiria is a neurological disorder in which patients respond to stimuli in which patients respond to stimuli originating on one side of their body as if they had been produced on the opposite side. A disorder in which visuoperceptive and attentional disturbances occur as a result of lesions in the parietal lobe of the brain.

In this article we explain in more detail what this disorder consists of, what are its possible causes, what types of allokiria exist and what is the indicated treatment.

What is Allokiria?

The aloquiria is a neurological disease, described at the end of the XIXth century by the Austrian neurologist Heinrich Obersteiner, that causes spatial transpositions in the patientIn other words, stimuli presented on one side of the body (or in space) are perceived as if they were presented on the opposite side.

For example, if the person is touched on the right shoulder, he/she will have the sensation that the left shoulder has been touched (somatosensory allokiria, when the tactile function is affected). In cases where the auditory or visual function is affected, patients report hearing sounds or voices on the opposite side to the one on which they were actually presented; and with regard to images or perceived objects, the affected persons report the same thing, that they perceive them on the opposite side to the one presented.

Allokiria has also been considered as another sign of spatial hemineglect, an attention disorder characterized by the inability to orient and respond to stimuli or objects located in one half of space (usually the half opposite to the damaged cerebral hemisphere). The person would show "indifference" to everything that happens on the left (or right) side of his or her reality..

In the vast majority of disorders in which allokiria is present, such as neglect syndromes or unilateral inattention syndrome, there is usually a lesion in the right parietal lobe.

Possible causes of this disorder

There are multiple theories that would explain why a disorder such as Allokiria occurs. But the most current and widely accepted explanation is Hammond's theorywhich states that there is a crossover or almost complete decussation of sensory fibers within the cerebral gray matter.

This theory concludes that if a lesion occurs on one of the posterior sides, it can reach the center of the corresponding cerebral hemisphere and, therefore, the sensation is referred by this hemisphere to the opposite side of the body, the sensation is referred by this hemisphere to the opposite side of the body..

Likewise, if another unilateral lesion is superimposed at a different level from the first, the sensation that was previously diverted to the wrong hemisphere may now be redirected upon encountering another obstacle, and thus may reach the right hemisphere. Allokiria would occur equally with both unilateral and bilateral lesions, as long as they are asymmetrical..

Another theory that would explain the causes of this neurological disorder would be Huber's theory, which postulates that the appearance of a new lesion on the opposite side redirects the impulse towards its original destination.

Types of allokyria

Let's see below how many types of allokiria exist and what each of them consists of.

Electromotor alokiria

The electromotor alokiria is produced when there is a reflex crossover in the muscular stimulation and has been observed in the face has been observed in the face, the lower extremities and the upper extremities..

For example, when a stimulus is presented on the affected side, contraction of the opposite facial muscles occurs, using a current so weak that even the healthy part of the face does not react. There have also been cases in which pressure on one forearm produces movement in the opposite forearm.

The fact is that an electrical stimulus can manifest its effects in a distant area of the nervous system, and that area can be on the same side of the body or on the opposite side.This area can be on the same side of the body or on the opposite side, although it is generally more frequent on the opposite side since the representation of the contralateral extremities of the spinal cord are closer to each other than the homolateral extremities (of the same half of the body).

1. Motor allokyrie

In this type of allokyrie, if the patient is asked to perform a movement with the affected side of the body, he/she does it with the corresponding part of the opposite side and he has the impression (or the certainty for him) that he has executed it correctly.

2. Reflex Allokiria

People suffering from reflex alokiria respond to stimulation of, for example, the sole of the foot or the inner part of the thigh, evoking the corresponding reflex only on the opposite side.

3. Auditory alokiria

In cases of auditory allokyria, various investigations have been carried out and observations have recorded that when holding a tuning fork next to one of the ears, the patient responds with a number of symptoms, including Pain and deafness, the patient responds with a series of symptoms, including pain and deafness, in the opposite ear.in the opposite ear.

4. Visual Allokiria

In visual allokyria, the patient perceives objects on one side of the visual field on the contralateral side. In one study, the patient receiving visual stimulation through his right eye regularly reported that it was his left eye that was stimulated (even though it remained closed).

In another study, one of the patients was presented with a colored object in front of his left eye, and the patient always maintained that the color was perceived with his right eye.

5. Gustatory Allokiria

In cases of gustatory allokiria, the investigations carried out consisted of placing a particular substance on one side of the patients' tongue, with the expected result that all of them reported that they had tasted the same substance on the opposite side of their tongue..

In addition, when a piece of the tongue was palpated on one side, they also reported that the opposite side of their tongue had been touched.

Treatment

Although there is currently no validated and effective treatment, these types of neurological disorders, such as allokiria, which affect attentional capacity and visuoperceptive skills, are usually addressed through the implementation of a neurological rehabilitation program. the implementation of a neuropsychological rehabilitation program.. This intervention will depend on the etiology of the brain damage, the stage of the patient, as well as other variables and other deficits that may accompany the disorder.

Nonspecific interventions can be carried out, in which attentional function is treated as a unitary concept, working on aspects such as simple or complex reaction time, Stroop-type tasks, etc; or more specific interventions focused on rehabilitating certain attentional components, such as selective attention or arousal.

In cases in which there is a neglect or hemineglect syndromeIn addition to allokiria, techniques have been used such as prism adaptation, which enhances the lateralized reorganization of the visuomotor cartography, facilitating perceptual changes in the patient; optokinetic stimulation, which induces changes in the patient's attentional system through stimuli that capture the patient's attention and redirect it to the contralesional side; or behavioral techniques, such as positive reinforcement and reward, which have a great influence and modulate the patient's attentional processes.

On the other hand, in recent years, more and more interventions that use interventions using technologies such as virtual reality or cognitive training software are increasingly used in recent years.. Several studies have shown that these techniques can be useful in improving patients' alertness performance and attentional aspects.

Bibliographic references:

• Arnedo, M, Bembibre, J. and Triviño, M. (2013). Neuropsicología a través de casos clínicos. Madrid: Editorial Médica Panamericana.
• Halligan PW, Marshall JC, Wade DT. Left on the Right – Allochiria in a case of left visuospatial neglect. J Neurol Neurosurg Psychiatry 1992;55:717–9