Nervous tic

Tics are typically short, relatively elementary, stereotypical, normally coordinated but inappropriately performed movements that can be suppressed by willpower for a short period of time, which is achieved at the cost of increasing emotional tension and discomfort.

The term "tic" in practical neurology is often used as a phenomenological concept to denote any excessive and obscure movements, especially in the case of facial localization of dyskinesias. Such a broad interpretation of a tic is unjustified, since it only creates confusion in terminology. Among the known hyperkinetic syndromes (chorea, myoclonus, dystonia, tremor, etc.), a tic is an independent phenomenon and in typical cases is characterized by clearly defined clinical manifestations, knowledge of which reliably protects the doctor from diagnostic errors. Nevertheless, syndromic diagnostics of tics is sometimes very difficult due to their phenomenological similarity to choreic movements or myoclonic twitching, and in some cases to dystonic or compulsive movements. Sometimes tics are erroneously diagnosed with stereotypes, habitual body manipulations, hyperactive behavior, startle syndrome. Since the diagnosis of tics is always exclusively clinical, it is appropriate to dwell in more detail on their characteristic features.

Tics are repetitive, stereotypical movements that result from the sequential or simultaneous contraction of several muscle groups. Tics may be fast (clonic) or somewhat slower (dystonic). Most often, tics involve the face, neck, upper limbs, and less often the trunk and legs. Sometimes tics are manifested by vocalizations, such as involuntary coughing or grunting. Tics are usually preceded by a feeling of discomfort or an imperative need to perform a movement. Unlike chorea, myoclonus, or tremor, tics can be voluntarily delayed for a short period of time. The intellect of patients with tics usually remains intact, and there are no other pyramidal or extrapyramidal symptoms. Many patients with tics are combined with obsessive-compulsive disorder.

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Classification and causes of tics

• Primary (idiopathic): sporadic or familial tic hyperkinesias.
  • Transient tics.
  • Chronic tics (motor or vocal).
  • Chronic motor and vocal tics (Tourette's syndrome).
• Secondary tics (Tourettism).
  • For hereditary diseases (Huntington's chorea, neuroacancytosis, Hallervorden-Spatz disease, torsion dystonia, etc.).
  • In acquired diseases [traumatic brain injury, stroke, epidemic encephalitis, developmental disorders (autism, impaired mental maturation), intoxication (carbon monoxide), iatrogenic (neuroleptics, psychostimulants, anticonvulsants, levodopa).

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Primary (idiopathic) tics

Transient tics are usually used to denote a condition when single or multiple tics are observed for at least 2 weeks, but not more than 1 year. Tics are manifested not only by corresponding movements (motor tics), but also by certain vocal phenomena (vocal tics). Both motor and vocal tics are in turn divided into simple and complex.

• Simple motor tics are short, isolated movements such as blinking, head or shoulder twitching, forehead wrinkling, and similar basic movements.
• Complex motor tics are manifested by more complexly constructed and coordinated movements in the form of a series of linked movements reminiscent of plastic action or even more complex ritual behavior.
• Simple vocal tics include sounds such as wheezing, grunting, mooing, sniffling, snorting, and the like, or shouting out isolated sounds and squeals.
• Complex vocal tics have a linguistic meaning and contain complete or truncated words and, in addition, include such vocal phenomena as echo- and coprolalia. Echolalia is the patient's repetition of words or phrases spoken by another person (the speaker's repetition of his or her own last word is called palilalia). Coprolalia is the shouting or utterance of obscene or profane words (from the lexicon of obscene language).

Motor tics usually begin with single facial movements (single tics), and over time they begin to occur in many areas of the body (multiple tics). Some patients describe prodromal sensations of discomfort in one or another part of the body (sensory tics), which they try to relieve by performing a tic movement of that part of the body.

The motor pattern of tic hyperkinesis is very specific and difficult to confuse with any other hyperkinetic syndrome. The course of the disease is also distinguished by no less characteristic features. First of all, the occurrence of tics is typical for the first decade of life, and most children become ill at the age of 5-6 years (although variations are possible from 3-4 to 14-18 years). In the age periodization of childhood, this stage is called psychomotor development. Violation of the maturation of the psychomotor sphere is considered one of the factors contributing to the occurrence of tics.

At first, tics appear unnoticed by the child and parents. Only as they become fixed in behavior, parents and educators begin to pay attention to them. For a long time, tic movements do not cause any inconvenience to children and do not burden them. The child surprisingly “does not notice” his tics. As a rule, the immediate reason for contacting a doctor is the concerns of the parents.

The most typical onset of tics is in the facial area, especially characteristic is localization in the area of the orbicularis oculi and oris muscles. Tic movements include increased blinking (the most common type of tic onset), winking, squinting, wrinkling the forehead, etc. Twitching of the corner of the mouth ("grinning"), the wings of the nose, frowning, pursing of the lips, baring of teeth, licking of the lips, sticking out of the tongue, etc. may be observed. With other localization of tics, they are manifested by movements of the neck (turning the head, throwing it back and other, more complex bends of the muscles of the shoulder girdle), as well as muscles of the trunk and limbs. Here it should be noted that in some patients tics are manifested by slower, one might say, "tonic" movements, which resemble dystonia and are even designated by a special term - "dystonic tics". There is another type of tics, which we once called fast tics; they are manifested by quick, sometimes abrupt movements (shoulder twitching, shaking, short jerky movements like shuddering, abduction, adduction, jerky movements in the muscles of the neck, trunk, arms or legs). Complex motor tics sometimes resemble actions such as, for example, "throwing hair from the forehead", "freeing the neck from a tight collar" or more complex motor behavior in which tic movements are difficult to isolate from compulsive behavior, striking in its strange and fanciful plasticity, sometimes shocking and captivating. The latter is especially characteristic of Tourette syndrome.

Any tic, simple or complex, is based on the involvement of several functionally related muscles, so the motor act in a tic looks like an expedient action. Unlike other classical forms of violent movements (chorea, ballismus, myoclonus, etc.), tic movements are distinguished by harmonious coordination, which is normally inherent in voluntary movements. For this reason, tics disrupt motor behavior and social adaptation less than other hyperkinesis (social maladaptation in Tourette syndrome is associated with other specific manifestations of this syndrome or severe comorbid disorders). Tics are often similar to natural ones in their origin, but exaggerated in their expressiveness and inadequate to the place and time (inappropriate) gestures. This is also consistent with a number of other facts: a fairly high level of volitional control over tics, the ability to replace (if necessary) a habitual tic movement with a completely different motor act, the ability to quickly and accurately reproduce tics.

The course of tics is so unique that it carries the most important diagnostic information. Let us recall that in cases where patients remember the onset of the disease well, they usually point to facial tics as the first symptom of the disease. Later, hyperkinesis gradually “accumulates” with other tic movements, disappearing in some and appearing in others muscle groups. For example, tics can begin due to increased blinking, which, periodically resuming, lasts for 2-3 months, and then spontaneously passes, but is replaced by periodic movement of the corner of the mouth or tongue (head, hand, etc.), which, in turn, after holding on for some time (weeks, months), is replaced by new tic movements. Such a step-by-step migration of tic movements across different muscle groups with a periodic change in the localization of hyperkinesis and its motor pattern is very characteristic and has an important diagnostic value. At each stage of the disease, as a rule, 1 or 2 tic movements dominate, and the movements observed at the previous stage are absent (or occur much less frequently). Facial localization of tics is relatively more persistent. Thus, the disorder not only debuts with the facial muscles, but also, in a certain sense, "prefers" them to other segments of the body.

Tics can be quite severe, causing physical or psychosocial maladjustment. But in most cases they are relatively mild and represent more of a psychosocial problem. It has been established that approximately 1 in 1000 people suffer from this disease. There are familial cases of Tourette syndrome, indicating autosomal dominant inheritance with incomplete penetrance and variable expressivity. In family members of the patient, the suspected genetic defect may manifest itself as chronic motor tics or obsessive-compulsive disorder. The gene or genes for Tourette syndrome have not yet been identified.

Chronic tics (motor or vocal)

Having appeared in childhood, the disease tends to have a long (sometimes lifelong) course with wave-like exacerbations and remissions: periods of pronounced tics alternate with periods of their complete or partial remission. Tics that periodically appear for more than 12 months are called chronic motor or vocal tics. Sometimes tics spontaneously cease during puberty or post-puberty. If they do not pass during this critical period, they usually persist for an indefinite period. Nevertheless, the prevailing tendency is, apparently, an improvement in the condition. After many years, about a third of patients are still free of tics, another third notes a certain improvement in their condition, the remaining patients note a relatively stationary course of tic hyperkinesis. Tics usually intensify under the influence of psychotraumatic situations, stress, prolonged emotional tension and, on the contrary, decrease in a situation of emotional comfort, relaxation and disappear during sleep.

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Tourette syndrome (chronic motor and vocal tics)

If earlier idiopathic tics and Tourette syndrome were considered as diseases of fundamentally different nature, today many neurologists are inclined to consider them as different manifestations of the same disease. Recently, the clinical criteria of Tourette syndrome were such manifestations as coprolalia and so-called autoaggressive tendencies in behavior (tics in the form of hitting surrounding objects and, more often, one's own body). At present, it has been established that coprolalia can be transient and occurs in less than half of patients with Tourette syndrome. The modern diagnostic criteria of Tourette syndrome are as follows.

• The presence of multiple motor tics plus 1 or more vocal tics over a period of time (not necessarily simultaneously).
• Multiple occurrences of tics during the day, usually in clusters, nearly every day for a period of more than 1 year. During this time there should be no tic-free episodes lasting more than 3 consecutive months.
• Marked distress or significant impairment in the patient's social, occupational, or other functioning.
• Onset of the disease before the age of 18.
• The identified violations cannot be explained by the influence of any substances or general disease.

In recent years, the above diagnostic criteria (DSM-4) have been supplemented with criteria for definite and probable Tourette syndrome. A definite diagnosis corresponds to the above diagnostic requirements. The diagnosis of Tourette syndrome is considered probable if the tics do not change over time and have a persistent and monotonous course, or the patient does not correspond to the first point of the above diagnostic requirements.

An important feature of the clinical manifestations of Tourette syndrome is that it is very often combined with certain behavioral disorders, the list of which includes obsessive-compulsive disorders, minimal brain dysfunction syndrome (hyperactive behavior, attention deficit syndrome), impulsivity, aggressiveness, anxiety, phobic and depressive disorders, self-harm, low frustration tolerance, insufficient socialization and low self-esteem. Obsessive-compulsive disorders are noted in almost 70% of patients, they are considered one of the most common comorbid disorders. Almost every second patient with Tourette syndrome is diagnosed with attention deficit hyperactivity disorder, with the same frequency of self-harm. Some researchers believe that the indicated comorbid behavioral disorders are nothing more than a phenotypic manifestation of Tourette syndrome, most cases of which develop against the background of a hereditary predisposition. It is believed that Tourette syndrome is much more common than is diagnosed, and that the population is dominated by patients with mild and maladaptive manifestations of the disease. It is also assumed that behavioral disorders may be the only manifestation of Tourette syndrome.

Unlike obsessive movements, the desire to perform a tic is either poorly understood at all, or is understood not as a pathological phenomenon, but as a physiological need and without the personal arrangement that is characteristic of the corresponding psychopathy. Unlike tics, compulsions are accompanied by obsessions and are often carried out in the form of rituals. It is important to note that comorbid disorders with respect to tics are true obsessive-compulsive disorders. Moreover, in some patients with Tourette syndrome, tics and compulsions represent a single behavioral phenomenon, manifested by a vivid and unusual clinical picture, in which it is not always easy to isolate its main constituent elements.

Secondary tics (tourettism)

This variant of tic syndrome is observed much less frequently than primary forms; it is possible in both hereditary (Huntington's chorea, neuroacancytosis, Hallervorden-Spatz disease, torsion dystonia, chromosomal abnormalities, etc.) and acquired (traumatic brain injury, stroke, encephalitis, developmental disorders, intoxication, iatrogenic forms) diseases.

In these cases, along with typical clinical manifestations of the underlying disease (e.g., Huntington's chorea, dystonia, neuroleptic syndrome, etc.), the phenomenon of vocalization and tic movements (in addition to the underlying hyperkinesis or other neurological manifestations) occur. The main method of diagnosing tics is also their clinical recognition.

Neurochemical changes

To date, only a few patients with Tourette syndrome have been pathologically examined, and no specific pathological or neurochemical changes have been identified. However, several postmortem neurochemical studies have shown changes in dopaminergic activity. A recent neuroimaging study of monozygotic twins with Tourette syndrome showed that the twin with more severe clinical manifestations had a higher number of dopamine D2 receptors in the striatum. MRI has shown that patients with Tourette syndrome have lost the normal asymmetry of the right and left caudate nuclei. Functional MRI and PET activation studies indicate dysfunction of the orbitofrontal-caudate circle.

It has been noted relatively recently that some individuals with Sydenham's poststreptococcal chorea, in addition to chorea itself, have tics and obsessive-compulsive disorder. In this regard, there have been suggestions that some cases of tics have an autoimmune genesis and are associated with the formation of antibodies to antigens of the caudate nucleus, which is provoked by streptococcal infection.