Synkinesia: what it is, types, characteristics and treatment

These involuntary movements are sometimes the result of a disorder. Let's see what they look like.

Surely, many people who have tried to play a piano for the first time have had the same problem: when trying to play with both hands it was impossible because, unconsciously, both hands moved the same fingers.

This is called synkinesia and is a relatively common phenomenon, especially in childhood.especially in childhood. It is simply making an involuntary movement when doing a voluntary movement.

Although it may not be serious, there are cases in which it is a symptom of a severe neurological disease. Next we will discover what synkinesias are, what types there are, how they are produced and what treatments exist at the present time.

What is synkinesia?

The word synkinesia refers to the involuntary Muscle contraction associated with a voluntary movement.. That is, these are uncontrolled movements that are produced by the fact of making a controlled movement with another limb or region of the body.

It is basically the difficulty in individualizing, dissociating or coordinating the voluntary movement and preventing other unwanted movements from being generated.

In many cases, these involuntary movements are symmetrical and contralateral to the voluntary ones.In many cases, these involuntary movements are symmetrical and contralateral to the voluntary ones, as it can be, for example, to move the fingers of a hand and that the same fingers of the other one also do it. Also common are those of the face, such as smiling and, involuntarily, inducing contraction of the eye muscles, causing the person to squint a little when smiling.

These types of unwanted movements are common in infancy, and can be considered a non-pathological sign that the nervous system is still developing.. Normally, however, from the age of 10 to 12 years, synkinesias attributed to normotypic growth begin to disappear.

Types of synkinesias

There are different types of synkinesias taking into account two criteria. One refers to the region of the body affected and type of movement, while the other refers to whether they are synkinesias to be expected in normal development or whether they are the result of some type of neurological lesion.

Depending on the region involved

Depending on the region involved, we can talk about three main types of synkinesia:

1. facial synkinesia

It is usually produced by paralysis of the facial nerve. Also called Bell's palsy or facial paralysis, it is believed that behind this neurological problem there could be a viral cause..

The main type of synkinesia that occurs in this condition is that when you try to smile or move your mouth, you also move muscles that you do not want to activate, making it difficult to speak, eat or swallow saliva.

2. Extraocular muscle synkinesia

The six muscles around the eye are innervated by three different cranial nervesabducens (VI cranial nerve), trochlear (IV cranial nerve) and oculomotor (III cranial nerve).

Following trauma near the eye, these muscles may fail to activate, causing pupil retraction and constriction to be altered.

3. Bimanual synkinesia

Bimanual synkinesia occurs when the upper limbs, and in particular the hands and fingers, perform exactly the same type of movement, even though only the hands and fingers are to be activated.even though only one hand is to be activated voluntarily.

This is called mirror hand movements, and may persist throughout life. Although they need not be pathological, they can occur in severe conditions such as Parkinson's disease and Kallmann's syndrome.

According to their degree of normality

There are synkinesias that are due to normal physiological processes, especially during childhood. However, there are other cases that can be considered pathological.

1. Physiological synkinesias

Physiological synkinesias, especially in childhood, are completely normal involuntary movements and do not necessarily mean that there is a neurological problem..

A clear example of this type of synkinesia would be the bimanual, observable when learning to play the piano even in adulthood. It is very difficult for us to dissociate the movements of one hand with the other, unless it is practiced.

Another example of normal synkinesis is the movement we make with our arms while walking. While walking we move the right arm forward and, at the same time and unconsciously, we move the left arm backward.

2. Pathological synkinesias

There are several synkinesias that could be considered pathological, associated with trauma and neurological diseases..

On the one hand, we have the imitation synkinesias, which consist of symmetrical and identical contralateral movements, in which the altered limb moves imitating the healthy limb.

On the other hand, we have global synkinesias, in which when trying to move a single group of muscles, others are activated, making daily life difficult for the affected person. It usually occurs in diseases that cause hemiplegia.

Mechanisms

Three neurological mechanisms have been proposed to explain synkinesia.

Abnormal nerve regeneration.

The hypothesis of anomalous nerve regeneration is the most widely accepted mechanism to explain synkinesias. This hypothesis holds that, after having suffered a trauma, axons project from the facial nucleus to the wrong peripheral muscles..

These anomalous connections may simultaneously innervate different subdivisions of the facial nerve. As a result, when these pathways are activated, muscles are stimulated that are not intended to be activated voluntarily.

Ephaptic transmission

Another explanation that has been put forward to explain synkinesia is that of ephaptic transmission. Basically, this theory holds that non-synaptic contacts are sometimes established between neighboring nerve fibers.

When one of them receives a nerve impulse, this also passes through the neighboring fibers because they are in close proximity to each other.This also stimulates and, therefore, activates muscles that were not intended to be activated in the first place.

Nuclear hyperexcitability

The nuclear hyperexcitability hypothesis holds that axonal degeneration can occur after injury.

The postsynaptic cell downstream of this injured axon, not receiving nerve stimulation, becomes increasingly sensitive to neurotransmitters, as a result of the injury. to neurotransmitters, as if its tolerance to them were reduced. As a consequence, if nearby undamaged axons release neurotransmitters, this cell deprived of its original axon receives stimulation from neighboring neurons, sending an impulse that does not correspond to it.

How are they evaluated?

To find out if there are synkinesias, there are different maneuvers to explore the movements, both voluntary and involuntary. Generally, consists of having them make a voluntary movement involving fine motor skills, although gross motor skills will also need to be explored.although gross motor skills will also need to be explored.

The patient may be asked to handle different objects or make different gestures with the face and hands to see if these voluntary movements are replicated in other regions of the face or on the ipsilateral side of the body.

Treatment

As we have mentioned, synkinesias do not have to be a pathological problem. Children present them as a sign of their still immature nervous system, and also some adults may present involuntary movements that are no more than slight annoyances in some of their daily activities.

However, there are there are cases in which one should be concerned, especially if the degree of intrusion of the involuntary movement is so great that it makes the day-to-day life of the affected person very difficult. of the affected person. Below we will look at different therapeutic approaches.

1. Facial training

The idea behind facial training is that neurons are not static. neurons are not static.. That is, they create new projections depending on the stimuli they receive.

To reduce synkinesia, facial training teaches the patient techniques to increase the desired techniques to increase the desired movements while also focusing on reducing involuntary movements..

For example, if the mouth always moves when the patient voluntarily blinks, the easy training technique will teach the patient to slowly close their eyes while actively focusing on keeping the mouth closed while making this movement.

2. Botox

Botulinum toxin is being used to reduce synkinesias. It was originally used to reduce hyperkinesia after suffering from facial paralysis, but it was found to be it was seen that it could be useful to work on involuntary movements, being able to be reduced in just 3 days.. 2 or 3 botox sessions can make the involuntary movement disappear forever.

3. Surgery

Among the surgical procedures to treat synkinesia are neurolysis and selective myectomy.. Neurolysis has been shown to be effective in reducing synkinesia but only temporarily and, unfortunately, symptoms may return, sometimes even increased.

In selective myectomy, the muscle that has presented synkinesic movement is selected and removed or annulled. It is a much more effective technique, but it has the problem of postoperative complications. postoperative complications can occur, including medical problems such as edema, hematomas and ecchymosis..

It is because of these problems that surgical interventions to treat synkinesia are rarely resorted to.

Bibliographic references:

• Victor, M., Ropper, A. H., & Adams, R. D. (2001). Principles of neurology (Vol. 650). New York: McGraw-Hill.
• Rodriguez-Ortiz MD, Mangas-Martinez S, Ortiz-Reyes MG, et al (2011). Rehabilitation of synkinesia and facial asymmetry in patients with peripheral facial palsy using the electromyographic biofeedback technique. Arch Neurocien. 16(2):69-74.