Synkinesia: what it is, type, characteristics and treatment

True, many people who tried playing the piano for the first time had the same problem: when trying to play with both hands, it was impossible because, unconsciously, both hands were moving the same fingers.

This is called synkinesia and it is a relatively common phenomenon, Especially in childhood. It is simply a matter of making one movement involuntarily when another is done on purpose.

Although it may not be serious, there are cases when they are symptoms of serious neurological disease. Below, we’ll find out what synkinesis is, what its types are, how they occur, and what treatments are currently available.

    What is synkinesis?

    The word synkinesis refers to the involuntary muscle contraction associated with voluntary movement. In other words, they are uncontrolled movements that occur due to movement controlled by another limb or another area of ​​the body.

    This is essentially the difficulty of individualizing, dissociating or coordinating voluntary movements and preventing the generation of other undesirable movements.

    In many cases, these involuntary movements are symmetrical and contralateral to the volunteers., Like moving the fingers of one hand and doing the same with the fingers of the other. Also common are those of the face, such as smiling and, involuntarily, twitching of the eye muscles, causing the person to twitch a bit in the iron smile.

    This kind of unwanted movements are common in childhood and can be taken as a non-pathological sign that the nervous system is still developing. However, normally, from 10 to 12 years of age, the synkinesias attributed to normotypic growth begin to disappear.

    Types of synkinesia

    There are different types of synkinesis taking into account two criteria. One refers to the area of ​​the body affected and the type of movement, while the other refers to whether synkinesia is expected in normal development or is the result of some type of injury. neurological.

    Depending on the region concerned

    Depending on the region concerned, we can talk about three main types of synkinesis:

    1. Facial synkinesia

    It is usually caused by paralysis of the facial nerve. Also called Bell’s palsy or facial palsy, 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 are also moving muscles that you don’t 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 pairs: abducens (cranial pair VI), trochlear (cranial pair IV) and oculomotor (cranial pair III).

    After trauma near the eye, there may be errors in the activation of these muscles, causing the pupil to retract and contract.

    3. Bimanual synkinesia

    Bimanual synkinesia it occurs when the upper limbs, and especially the hands and fingers, perform the exact same type of movement, Although you only want to voluntarily activate one hand.

    These are called hand mirror movements and can persist throughout life. Although they are not necessarily pathological, they can occur in serious conditions such as Parkinson’s disease and Kallmann syndrome.

      According to its degree of normality

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

      1. Physiological synkinesias

      Physiological synkinesia, especially in childhood, these are completely normal involuntary movements and should not mean that you have a neurological problem.

      A clear example of this type of synkinesis would be bimanual, observable when learning to play the piano even in adulthood. It is very difficult for us to separate the movements of one hand from 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 our right arm forward, and at the same time and unconsciously, we move our left arm backward.

      2. Pathological synkinesias

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

      On the one hand, we have those of imitation, 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, by trying to move a single group of muscles, others are activated, making the daily life of the affected person difficult. It usually occurs in diseases that cause hemiplegia.

      mechanisms

      Three neurological mechanisms have been proposed to explain synkinesis.

      Abnormal nerve regeneration

      The hypothesis of abnormal nerve regeneration is the most accepted mechanism to explain synkinesia. This hypothesis maintains that, after suffering a trauma, axons project from the facial nucleus to the bad peripheral muscles.

      These abnormal connections can innervate simultaneously in different subdivisions of the facial nerve. This means that when these pathways are activated, muscles are stimulated that do not want to be activated on purpose.

      efaptic transmission

      Another explanation that has been studied to explain synkinesis is that of effaptic transmission. Basically, this theory holds that nonsynaptic contacts are sometimes made between neighboring nerve fibers.

      When one of them receives a nerve impulse, it also passes through the neighboring fibers because they are very close to each other., Also causing them to be stimulated and thus muscles which, in principle, were not meant to be activated.

      nuclear hyperexcitability

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

      The postsynaptic cell that comes after this injured axon, not receiving nerve stimulation, becomes more and more sensitive. neurotransmitters, as if their tolerance to them was reduced. As a result, if nearby undamaged axons release neurotransmitters, that cell deprived of its original axon receives stimulation from neighboring neurons, sending a pulse that does not match it.

      How are they evaluated?

      To find out if there is synkinesia, there are different maneuvers to explore the movements, both voluntary and involuntary. in general it consists in making them make a voluntary movement in which fine motor skills are involved, Although it is also necessary to explore gross motor skills.

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

      treatment

      As we have seen, synkinesia does not have to be a pathological problem. Children present them as a sign of their still immature nervous system, and some adults may also experience involuntary movements that are nothing more than mild discomfort in some of their daily activities.

      However, yes there are cases when they need to worry, especially if the degree of interference from involuntary movement is so great that it makes everyday life very difficult of those affected. Below we will look at different pathways therapeutic.

      1. Facial training

      The idea behind facial training is that neurons are not a static thing. In other words, they create new projections based on the stimuli they receive.

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

      For example, if the mouth is still moving when the patient is blinking on purpose, the easy training technique will teach the affected person to slowly close their eyes while actively focusing on keeping the mouth closed while doing so. movement.

      2. Botox

      Botulinum toxin is used to reduce synkinesia. It was originally used to reduce hyperkinesia after facial paralysis, however we have seen that it could be useful to work on involuntary movements, being able to be reduced in just 3 days. 2 or 3 sessions of botox can lead to the permanent disappearance of involuntary movements.

      3. Surgery

      Some of the surgeries to treat synkinesia include selective neurolysis and myectomy. Neurolysis has been shown to be effective in reducing synkinesia, but this is only temporarily and unfortunately symptoms may reappear or even increase.

      In selective myectomy, the muscle that exhibited / displayed synkinesic movement is selected and is removed or canceled. This is a much more efficient technique, but it has the problem that postoperative complications can occur, including medical problems such as edema, bruising and bruising.

      It is because of these problems that surgeries to treat synkinesia are hardly used.

      Bibliographical references:

      • Victor, M., Ropper, AH and Adams, RD (2001). Principles of Neurology (Vol. 650). New York: McGraw-Hill.
      • Rodríguez-Ortiz MD, Mànigues-Martínez S, Ortiz-Reis MG, et al (2011). Rehabilitation of synkinesis and facial asymmetry in patients with peripheral facial palsy with electromyographic biofeedback technique. Neuroceal arc. 16 (2): 69-74.

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