Dyskinesia or dyskinesia is a medical term that refers to abnormal , uncontrollable and involuntary movement due to excessive or inappropriate muscle activity
Next, we will see what these movement disorders are, what types of dyskinesias exist and what their risk factors are.
What are dyskinesias?
Dyskinesias or dyskinesias are movement disorders characterized by excessive or abnormal and involuntary movements .
Movement disorders can be classified into two major groups: rigid-hypokinetic syndrome or hypokinetic movements; and hyperkinetic movement disorders or dyskinesias.
Within this last group, that of dyskinesias, different types should be noted, each with its own symptoms and specific characteristics. What they do have in common is where this movement disorder usually occurs: mainly in the head, arms, legs, hands, lips or tongue.
Most dyskinesias are caused by an injury to a specific area of the brain, called the basal ganglia , a structure in charge of postural control and voluntary movement. However, as we will see later on, there are other types of dyskinesias, such as tardive dyskinesia, caused by the consumption of certain types of medication.
Types of dyskinesia
Most dyskinesias manifest themselves as an excess of abnormal and involuntary movements, and include mainly: tremors, chorea, dystonia, balism, tics, myoclonus and stereotypes.
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 (for example, 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 common cause is Parkinson’s disease, a disorder that can be initiated by tremors in a 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 happens 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 holds a position against gravity (e.g., extending the arms).
1.2. Intentional tremor
It occurs when you make a voluntary movement towards a target (such as when you scratch your nose) and usually gets worse as you get closer to it.
1.3. Kinetic Tremor
It is associated with any type of voluntary movement (such as opening and closing the eyes or turning the palms up and down).
1.4. Isometric tremor
It usually occurs when a muscle is voluntarily contracted without being accompanied by a movement (for example, when lifting a weight and holding it with our hands)
1.5. Task-specific tremor
It only happens when you perform specialised, goal-oriented tasks , such as writing by hand or speaking.
Chorea is a hyperkinetic movement disorder or dyskinesia characterized by a constant flow of involuntary, abrupt and brief movements , which can change from one area of the body to another in a completely random and unpredictable manner.
There are two groups of Koreas: acquired and hereditary. In the first group, the most frequent causes are drugs, stroke, pregnancy and Sydenham’s chorea (a bacterial infection). In the second group, the most common form is Huntington’s disease, a hereditary and neurodegenerative condition .
The intensity of the chorea is variable. Initially, this type of dyskinesia may present itself as a movement in which the person wiggles and moves in a semi-intentional manner (generating an impression of restlessness or nervousness in the observer). In more advanced stages, as in Huntington’s disease, this dyskinesia becomes more evident and in extreme cases may even interfere with breathing , speech or walking, and may lead to absolute disability for the patient.
Dystonias are dyskinesias characterized by involuntary muscle contractions, resulting 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 be 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, 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 cramp or writer’s dystonia, which consists of a feeling of clumsiness during writing, which causes both the speed and the flow of movement to decrease.
Ballism 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 days or weeks.
Most often it affects a hemicorpse (hemibalism), although occasionally it may involve a single limb (monobalism), both lower limbs (paraballism) or, as a testimony, all four limbs (bibalism).
This type of dyskinesia tends to remit during sleep , although hemibalism has been documented during the 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 injuries.
Tics are movement disorders and dyskinesias that are 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 increased need that eventually causes them to let go and tics to reappear, followed by a period of rebound with increased frequency of occurrence.
Myoclonies are short, fast and abrupt movements, like jolts, 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 :
In this type of myoclonus, the movement is preceded by the activation of the cortical representation area of the corresponding muscle. They usually appear in neurodegenerative diseases such as Alzheimer’s or corticobasal degeneration.
They include myoclonias that are related to other movement disorders such as tremor or dystonia, sharing similar pathophysiological mechanisms with them.
This type of myoclonus may be due to different spinal cord injuries . They appear spontaneously and may persist during sleep.
They are extremely rare, but cases have been described in peripheral nerve injuries.
This type of dyskinesias, which are characterized by repetitive, coordinated, non-propositional (which have no specific purpose) and rhythmic contractions, generate movements that can be suppressed by initiating other voluntary motor activity ; that is, stereotypes do not prevent the person from carrying out a motor activity but, on occasion, 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 neuroleptic drug use , without any other identifiable cause.
This type of dyskinesia involves 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 not aware of the development of tardive dyskinesia, but many with more serious disorders may present difficulties in chewing, 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 dysfunction; 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 being partly responsible for the symptoms of this movement disorder.
- Venegas, Pablo, Millán, María E. and Miranda, Marcelo. (2003). Disquinesia tardía (Late Dyskinesia). Chilean Journal of Neuropsychiatry, 41(2), 131-138
- Sanz García, A.I. and Martín Fernández, M.A. (1994). Late dyskinesia: applications of current knowledge to clinical practice. Spanish Journal of Pathology, 51.