Dyskinesia (or dyskinesia): types, symptoms, causes and characteristics.

A review of the characteristics of dyskinesia, a movement disorder.

Dyskinesia or dyskinesia is a medical term that refers to abnormal, uncontrollable and involuntary movement due to excessive muscular activity.uncontrollable and involuntary movement due to excessive or inappropriate muscular activity.

Next, we will see what these movement disorders consist of, what types of dyskinesias exist and what their risk factors are.

What are dyskinesias?

Dyskinesias or dyskinesias are movement disorders characterized by an excess of movements or by abnormal and involuntary movements..

Movement disorders can be classified into two major groups: the rigid-hypokinetic syndrome or hypokinetic movements; and hyperkinetic movement disorders or dyskinesias.

Within this last group, dyskinesias, there are different types, each with its own specific symptoms and characteristics. What they do have in common is where this alteration of movements that people with this disorder usually present occurs: mainly in the head, arms, legs, hands, lips or tongue.

Most dyskinesias are caused by a lesion in a specific area of the brain, called the basal ganglia, a structure responsible for postural control.a structure responsible for postural control and voluntary movement. However, as we will see below, there are other types of dyskinesias, such as tardive dyskinesia, caused by the consumption of certain types of drugs.

Types of dyskinesia

Most dyskinesias manifest as an excess of abnormal and involuntary movements, and include mainly: tremors, chorea, dystonia, ballism, tics, myoclonus and stereotypies.

1. Tremors

Tremors are characterized as a class of regular, rhythmic oscillatory movements, which may vary in length, amplitude or duration, produced by contractions of agonist and antagonist muscles.

Tremors usually subside with action (e.g., when the patient eats or writes) and therefore do not usually affect the subject's daily life as much.

There are two main classifications of tremor. On the one hand, there is the resting (or static) tremor.. This is the most common type of tremor and the most frequent cause is Parkinson's disease, a disorder that can start with these tremors in one limb (upper or lower). It usually occurs with the muscles at rest, relaxed and fully supported.

On the other hand, we have the tremor in action, which occurs with voluntary movement of the muscle.. Within this category, we can include the following:

1.1. postural tremor

This tremor occurs when the person maintains a position against gravity (e.g., extending the arms). (for example, extending the arms).

1.2. Intentional tremor

Occurs when performing a voluntary movement towards a target (e.g. when scratching the nose) and usually worsens when approaching the target.

1.3. Kinetic tremor

It is associated with any type of voluntary movement (such as opening and closing the eyes or turning up and down the palms of the hand).

1.4. Isometric tremor

It usually occurs when a Muscle is voluntarily contracted, without being accompanied by a movement (e.g. when lifting a weight). (for example, when lifting a weight and holding it with our hands).

1.5. Task-specific tremor

Occurs only when performing specialized, goal-oriented tasks, such as handwriting or talking.such as handwriting or speaking.

2. Chorea

Chorea is a hyperkinetic movement disorder or dyskinesia characterized by a constant stream of brief, jerky, involuntary a constant stream of involuntary, jerky, brief movements, which may change from one area to another.It is characterized by a constant flow of brief, jerky, involuntary movements that can shift from one area of the body to another in a completely random and unpredictable manner.

There are two groups of korea: acquired and hereditary. In the first group, the most frequent causes are usually drugs, stroke, pregnancy and Sydenham's chorea (a bacterial infection). In the second group, the most common form is Huntington's disease, an affective disorder. Huntington's disease, an inherited, neurodegenerative condition..

The intensity of chorea is variable. Initially, this type of dyskinesia may present as a movement in which the person wiggles and twitches in a semi-intentional manner (generating an impression of uneasiness or nervousness in the observer); in more advanced stages, such as in Huntington's disease, this dyskinesia becomes more evident and in extreme cases it may even interfere with breathing, speech or gait, and may even interfere with breathing, speech or walking.In more advanced stages, as in Huntington's disease, this dyskinesia becomes more evident and in extreme cases can even interfere with breathing, speech or walking, and can result in absolute disability for the patient.

3. Dystonia

The dystonia are dyskinesias characterized by involuntary muscle contractions, resulting in repetitive twisting movements and abnormal postures..

This movement disorder can manifest itself in various forms, affecting only one part of the body (focal type dystonia) or several parts, or generalized throughout the body.

There are primary forms of dystonia, which may be hereditary, in which case they usually begin at an early age and are generalized; and idiopathic forms, which originate in adulthood and are usually focal. Secondary forms of dystonia are associated with other movement disorders or central nervous system disorders.

The severity and type of dystonic movement varies depending on body posture, task to be performed, emotional state or level of consciousness. Some people also suffer from blepharospasms (involuntary contractions of the eyelids) and writer's cramp or scribal dystonia, which consists of a feeling of clumsiness during writing, causing both the speed and fluency of movement to decrease.

4. Ballism

Ballismus is a severe degree and a more violent form of chorea.. It usually affects multiple limbs and both sides of the body. Although it usually appears abruptly, it usually develops over a period of days or weeks.

It most often affects one hemibody (hemiballism), although occasionally it may involve only one limb (monoballism), both lower limbs (paraballism) or, to a lesser extent, all four limbs (biballism).

This type of dyskinesia tends to remit during sleep, although hemiballismus has been documented.although hemiballismus has been documented during light phases of sleep.

The movements produced by this disorder are so violent that they can sometimes lead to death by exhaustion or by causing joint or skin lesions.

5. Tics

The tics are disorders of the movement and dyskinesias generally brief and repetitive, abrupt and stereotyped, that vary in intensity and arise in irregular intervals..

Although they can be suppressed and avoided voluntarily and for a variable period of time, when this takes place the people experience an internal sensation of tension and increasing necessity that causes that finally they have to let go and the tics arise again, followed in addition by a period of rebound with increase in the frequency of occurrence of the same ones.

6. Myoclonias

The myoclonias are brief, rapid and abrupt movements, in the form of jerks, and with a variable amplitude. These dyskinesias are usually caused by muscle contractions (positive myoclonias) or abrupt inhibitions of muscle tone (negative myoclonias or asterixis).

These types of dyskinesias can be classified according to the structure of the nervous system in which they are generated:

Cortical

In this type of myoclonus, the movement is preceded by activation of the cortical representation zone of the corresponding muscle. They usually appear in neurodegenerative diseases such as Alzheimer's disease or corticobasal degeneration.

Subcortical

They include myoclonias that are related to other movement disorders such as tremor or dystonia, sharing similar pathophysiological mechanisms.

Spinal

This type of myoclonias may be due to different lesions in the spinal cord.. They appear spontaneously and may persist during sleep.

Peripheral

They are extremely rare, but cases have been described in lesions of the peripheral nerves.

7. Stereotypies

This type of dyskinesias, which are characterized by repetitive, coordinated, non-propositional (not having a specific purpose) and rhythmic contractions, generate movements that can be suppressed by initiating another voluntary motor activity.In other words, stereotypies do not prevent the person from performing a motor activity, but can sometimes interfere with normal tasks if they are very frequent or injurious.

8. Tardive dyskinesia

Tardive dyskinesias are a type of involuntary and abnormal movement which originates after a minimum of 3 months of use of neuroleptic drugs, with no other identifiable cause.without any other identifiable cause.

This type of dyskinesia includes abnormal movement of the tongue, lips and jaw, in a combination of gestures such as sucking, sucking and chewing, in a repetitive, irregular and stereotyped manner.

The vast majority of patients are unaware of the development of tardive dyskinesia, but many with more severe disorders may present with chewing difficulties, dental damage, dysphagia or dysarthria, etc.

Tardive dyskinesia occurs because neuroleptic drugs exert, on the one hand, a hypersensitizing effect on dopamine receptors, causing motor dysfunctions; and on the other hand, a destruction of GABAergic neurons responsible for inhibiting involuntary movements. A third hypothesis would also point to a release of toxic free radicals as partly responsible for the symptoms of this movement disorder.

Bibliographic references:

• Venegas, Pablo, Millán, María E. and Miranda, Marcelo. (2003). Tardive dyskinesia. Revista chilena de neuro-psiquiatría, 41(2), 131-138.
• Sanz García, A.I. and Martín Fernández, M.A. (1994). Tardive dyskinesia: applications of current knowledge to clinical practice. Spanish journal of pathology, 51.