Alloquiria: symptoms, causes and treatment

Allochiria is a neurological disorder in which patients respond to stimuli originating on one side of their body as if they had occurred 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 alloquiria exist and what is the indicated treatment.

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What is allochiria?

Alloquiria is a neurological disease, described at the end of the 19th century by the Austrian neurologist Heinrich Obersteiner, who causes in the patient spatial transpositions; that is, the stimuli that are presented to him on one side of the body (or space) he perceives as if they were presented on the opposite side.

For example, if the person's right shoulder is touched, they will have the sensation that their left shoulder has been touched (somatosensory allochyria, when tactile function is affected). In cases where 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 the images or perceived objects, the affected people report the same thing, that they perceive them on the opposite side to the one presented.

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

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

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Possible causes of this disorder

There are multiple theories that would explain why a disorder such as alloquiria occurs. But the most current and widely accepted explanation is Hammond's theory, which states that almost complete crossing over or decussation of sensory fibers occurs 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, sensation is referred by this hemisphere to the opposite side of the body.

Likewise, if another unilateral lesion is superimposed at a different level than the first, sensation that previously deviated to the wrong hemisphere, now it could be redirected when encountering another obstacle, and thus it could reach the wrong hemisphere appropriate. the alloquiria It would occur equally with both unilateral and bilateral lesions, as long as they are asymmetric..

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

• You may be interested in: "Cerebral hemispheres: myths and realities"

types of allochiria

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

electromotor allochiria

Electromotor allokyria occurs when there is a crossover of reflexes in muscle stimulation and has been observed on the face, lower extremities, and upper extremities.

For example, when a stimulus is presented on the affected side, contraction of the opposing facial muscles, using a current so weak that even the healthy part of the face reaction to. There have also been cases where pressing on one forearm causes 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, although it is generally more frequent that it is the opposite side since the representation of the contralateral limbs of the spinal cord are closer together than the ipsilateral limbs (of the same half of the body).

1. motor allochiria

In this type of allochyria, if the patient is asked to perform a movement with the affected side of the body, they do so 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 allochiria

People who suffer from reflex allochiria respond to stimulation, for example, from the plant of foot or inner thigh, evoking the corresponding reflex only on the left side. opposite.

3. auditory allochyria

In cases of auditory allochiria, various investigations have been carried out and the observations made have recorded that by holding a tuning fork next to one of the ears, the patient responds with a series of symptoms, including pain and deafnessin the opposite ear.

4. visual allochyria

In visual allochiria, the patient perceives objects located to one side of the visual field on the contralateral side. In one of the studies carried out, the patient who received visual stimulation through his eye right, regularly reported that it was his left eye that was stimulated (despite the fact that 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 allochiria

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

In addition, when a piece of the tongue was felt on one of its sides, they also reported that the opposite side to the one that actually corresponded had been touched.

Treatment

Although there is currently no validated and effective treatment, this type of neurological disorder, such as allochiria, which affect attention span and visuoperceptive skills, are usually addressed by the implementation of a neuropsychological rehabilitation program. This intervention will depend on the etiology of the brain damage, the phase in which the patient is, in addition to other variables and other types of deficits that may accompany the disorder.

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

In cases in which there is a syndrome of negligence or hemineglect, accompanied by alloquiria, techniques have been used such as the adaptation of prisms, which enhances the lateralized reorganization of visuomotor cartography, facilitating perceptual changes in the patient; optokinetic stimulation, which induces changes in the patient's attentional system through stimuli that capture their attention and redirect it towards the contralesional side; or behavioral techniques, such as positive reinforcement and reward, which exert a great influence and modulate the attentional processes of the patient.

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

Bibliographic references:

• Arnedo, M, Bembibre, J. and Trivino, M. (2013). Neuropsychology through clinical cases. Madrid: Panamerican Medical Editorial.
• 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