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

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

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

• Related article: "The 15 most frequent neurological disorders"

What are dyskinesias?

dyskinesias or dyskinesias are movement disorders that are characterized by excessive movements or abnormal and involuntary movements.

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

Within this last group, that of dyskinesias, it is worth noting different types, each one with its specific symptoms and characteristics. What they do have in common is where this alteration of movements that the women usually present occurs. people suffering from this disorder: mainly, in the head, arms, legs, hands, lips or language.

Most dyskinesias are caused by a lesion in a specific area of ​​the brain, called the basal ganglia.

, a structure in charge of postural control and voluntary movement. Although, as we will see later, there are other types of dyskinesias, such as tardive dyskinesia, caused by the consumption of a certain class of medications.

• You may be interested in: "Basal ganglia: anatomy and functions"

types of dyskinesia

Most dyskinesias manifest as excessive abnormal and involuntary movements, and mainly include: tremors, chorea, dystonia, ballismus, tics, myoclonus, and stereotypes.

1. tremors

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

The tremors usually subside with the action (for example, when the patient eats or writes) and, therefore, does not usually affect the subject's daily life as much.

There are two main classifications of tremor. On the one hand, there is the tremor at rest (or static). It 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 extremity (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 the 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 (for example, extend your arms).

1.2. intention tremor

Occurs when making a voluntary movement towards a target (like when we scratch our nose) and, normally, it tends to get worse when approaching it.

1.3. kinetic tremor

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

1.4. isometric tremor

It usually occurs by voluntarily contracting a muscle, without being accompanied by a movement (for example, when lifting a weight and holding it with our hands)

1.5. Task-specific tremor

only happens when specialized tasks are carried out and oriented to a specific objective, such as writing by hand or speaking.

2. Korea

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

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

The intensity of the chorea is variable. Initially, this type of dyskinesia may present as a waddling movement. and moves semi-intentionally (generating an impression of restlessness 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 can even interfere with breathing, speech or walking, which can lead to absolute disability for the patient.

• You may be interested in: "Huntington's chorea: causes, symptoms, phases and treatment"

3. dystonia

Dystonias are dyskinesias characterized by involuntary muscle contractions, which result in repetitive twisting movements and abnormal postures.

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

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

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

4. ballism

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

Most frequently, it affects one side of the body (hemiballism), although occasionally it can affect only one. extremity (monobalism), to both lower limbs (parabalism) or, testimonially, to all four extremities (bibalism).

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

The movements produced by this disorder are so violent that they can sometimes lead the person to death, due to exhaustion or by causing joint or skin injuries.

5. ticks

Tics are movement disorders and dyskinesias usually brief and repetitive, abrupt and stereotyped, varying in intensity and arising at irregular intervals.

Although they can be suppressed and avoided voluntarily and for a variable period of time, when this occurs people experience an internal feeling of tension and increasing need that finally makes them have to let go and the tics reappear, followed by a period of rebound with an increase in the frequency of occurrence of tics. the same.

6. myoclonus

Myoclonus 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 myoclonus) or sudden inhibitions of muscle tone (negative myoclonus or asterixis).

This type of dyskinesia They can be classified according to the structure of the nervous system in which they are generated.:

cortical

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

subcortical

They encompass myoclonus that is related to other movement disorders such as tremor or dystonia, sharing similar pathophysiological mechanisms with them.

spinal

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

peripherals

They are extremely rare, but cases have been described in peripheral nerve injuries.

7. stereotypes

This type of dyskinesia, which is characterized by being repetitive, coordinated, non-purposive (which do not have a specific purpose) and rhythmic contractions, generate movements that can be suppressed by initiating another voluntary motor activity; that is to say, the stereotypes do not prevent the person from carrying out a motor activity but, on occasions, they can interfere with normal tasks if they are very frequent or harmful.

8. tardive dyskinesia

Tardive dyskinesias are a type of involuntary and abnormal movement that originates after a minimum of 3 months of use of neuroleptic drugswithout 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.

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

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

Bibliographic references:

• Venegas, Pablo, Millan, Maria E. and Miranda, Marcelo. (2003). Tardive dyskinesia. Chilean Journal of Neuro-Psychiatry, 41(2), 131-138
• Sanz Garcia, A.I. and Martín Fernández, M.A. (1994). Tardive dyskinesia: applications to clinical practice of current knowledge. Spanish journal of pathology, 51.