Functional tics or Tourette's - the subtle difference

Gilles de la Tourette syndrome (GTS) is one of the common neuropsychiatric disorders. It is predominantly genetically determined and is based on neuroanatomical and neurophysiological abnormalities. Accordingly, the disease is much more than swearing and uttering curse words.

Gilles de la Tourette syndrome (GTS) is one of the common neuropsychiatric disorders, with a prevalence ranging from 0.3% to 1% of the general population, depending on the literature. Therefore, and with steadily increasing media presence of this clinical picture, recently more and more medical colleagues are confronted with patients who suspect this disease in themselves.

According to the DSM-5, a prerequisite for the diagnosis of GTS is the occurrence of at least one vocal tic and several motor tics with onset before the age of 18 and lasting for at least one year. Typically, the first tics occur during elementary school age (4-9 years of age). These are mostly simple motor tics in the facial area such as increased blinking, eye rolling, eye squinting, or jerky movements of the head, for example. It is typical that the tics do not remain constant over a long period of time, but change during the course. More complex motor tics may also occur, such as squatting, twisting of the body, or jerky movements of the extremities. A concerted sequence of several movements is also possible. Usually a few years after the onset of motor tics, the first vocal tics appear. Here, too, the spectrum is wide. Possible sounds are single syllables, words, or rarely short sentences or exclamations, in addition to single sounds such as “grunt”, “clear throat”, “squeak”, or “gasp”.

In addition to echoic phenomena, i.e., imitating observed gestures (echopraxia) or repeating heard sounds or words (echolalia), coprophenomena in the form of vulgar gestures (copropraxia) or words (coprolalia) are also possible. Although coprofemias occur in only about one in five GTS patients, they often dominate media coverage, leading to a distorted public perception of the disease and thus to significant distress for patients who do not have coprofemias and their families.

Differentiating between tics in the context of GTS and other movement disorders can be difficult. Here, it is important to note that tics are usually short, phasic, repetitive same movements. It is also typical that tics occur in groups (so-called “bouts”) over time. Tics can bear great resemblance to physiological spontaneous movements. Viewed in context, however, they usually appear inappropriate, out of place or exaggerated. Also typical is the ability of patients to suppress tics at least temporarily, which is usually not possible in other classic movement disorders, e.g., myoclonus or chorea. A dependence of the complaints on cognitive processes (increase in tic frequency with stress and concentration on tics, decrease with distraction) can also be used as a distinguishing feature from classic movement disorders.

One of the main characteristics of GTS, besides the actual tics, is the premonitory urge that precedes them. This typically first appears several years after the onset of the first tics, usually around the age of 10. This is often an inner tension or an inner urge to act. In some cases, this is also described as a different sensory perception, for example, a feeling of warmth or cold or a feeling of tension in the muscles involved in the execution of the tic. Typically, suppression of tics leads to an increase, and tic execution leads to a temporary decrease in this feeling. In most cases, patients find the premonitory sensation very unpleasant and it often leads to severe impairment of the ability to pay attention and concentrate.

Psychiatric comorbidities are more frequent in GTS patients. 60% have concomitant attention deficit hyperactivity disorder, while anxiety and obsessive-compulsive disorders are present in 40%. Furthermore, depressive disorders and disorders of self-esteem are also not uncommon.

Course and therapy

Fortunately, the course of GTS is benign in most cases. While it is typically around the 10th-11th centuries. After a peak in symptoms at the age of 18, there is usually a marked decrease by the age of 18. In adulthood, most patients are symptom-free. Against this background, specific therapy is often not required. However, if the symptoms cause a high degree of distress or persist into adulthood, some treatment options are available. Antipsychotics (dopamine antagonists) have proven to be effective. Commonly used, in addition to tiapride as the first choice in children and aripiprazole as the first choice in adult patients, are other neuroleptics such as sulpiride or pimozide. Alpha-2 agonists such as guanfacine also find application. In addition, specific psychotherapy procedures such as “habit reversal therapy” are available. The two main elements of this therapy, also known as “habit reversal,” are adequate self-awareness of the tics and learning a “competing response.” In specific cases with focal, low-variability tics, often in the jaw or neck, symptomatic therapy with botulinum toxin injections may be helpful. Deep brain stimulation, primarily of the globus pallidus internus, has also been shown to be helpful in principle, but should be performed exclusively in the context of clinical trials.

Etiology and pathophysiology

Research into the triggering factors of GTS dates back to 1885, when the French neurologist and forensic pathologist George Gilles de la Tourette first described this syndrome. While initially a psychiatric or psychosomatic cause was assumed, this theory was abandoned around 1950 as diagnostic procedures improved. Today, a variety of neuroanatomical, neurophysiological, perceptual, and cognitive-psychological features in GTS patients, in addition to a genetic predisposition, are considered certain.

Neuroanatomical and neurophysiological features

Some of these abnormalities are found in the area of the basal ganglia, more precisely in the area of the cortico-striato-thalamo-cortical control circuit, which is particularly important for the initiation, planning and execution of movements. One of the most constant features here is a decrease in volume of the striatum. However, changes in the connectivity of the individual components to each other could also be demonstrated.

In the cortex, GTS patients also show a number of peculiarities. This includes, among other things, a decrease in gray matter volume in the area of the prefrontal cortex. Of particular importance are abnormalities in the supplementary motor area (SMA). This cortical segment, located in the middle part of Brodmann area 6, is thought to play an important role in the planning and initiation of movements, among other things. Fittingly, a tic-associated increase in activity was shown in GTS patients. Inhibition of this area by transcranial magnetic stimulation was able to reduce tic frequency in children with GTS.
At this point, the inferior parietal cortex (Brodmann area 40) should also be mentioned. Since this is responsible for the coupling between perception and action, which seems to be disturbed in GTS patients (see below), this section of the cortex is also receiving increasing attention.

Further peculiarities can be found in the area of neurotransmitter balance. Overactivity of the dopaminergic system is evidenced in part by the good therapeutic effect of dopamine antagonists such as aripiprazole.

Perceptual and cognitive psychological abnormalities.

Numerous studies demonstrate alterations in the perception, processing, and selection of sensory inputs and actions in GTS patients. An example of this is impaired inhibitory control, i.e., a reduced ability to tune out irrelevant stimuli, as shown, for example, by experiments with Stroop, Flanker, Simon, or Go/noGo tasks. Interoceptive perception, i.e. the perception of one’s own body, for example in the form of one’s own heartbeat, is also significantly reduced in GTS patients.

Of particular importance in the area of altered perceptual processes is the somatosensory system. On the one hand, this results from the typical somatosensory perceptions, referred to as pre-sensations, which typically precede the tics (see above). Also, about 80% of GTS patients report hypersensitivity to external stimuli, so that, for example, skin contact with a chair or washing instructions in a sweater can be perceived as very unpleasant.

Since, on the one hand, GTS patients often regard tics as a reaction to the preceding pre-feeling and, on the other hand, tic execution leads to a temporary decrease of this pre-feeling, there seems to be a particularly strong connection between perceptions and actions in GTS patients, which may be causally involved in tic development. To address this question, the multidisciplinary research group TEC4Tic (“Cognitive theory for Tourette syndrome – a novel perspective”, DFG FOR 2698) was launched in 2019. The basis for this is the “Theory of Event Coding” (TEC) developed by Bernhard Hommel. It represents a framework concept or cognitive basis for processes of perception and action. It is assumed that perceptions are stored in so-called “object files” and actions in so-called “action files”. According to TEC, this is by no means done independently of each other, but rather according to the same codes, interdependent and related to each other, so that so-called “event files” are created through a coupling between “object files” and associated “action files”. This means that sensory consequences resulting from an action are associated with it and vice versa. Importantly, an established “event file” is activated by a stimulus it contains and is then completely retrieved, which is referred to as “pattern completion logic.” Also, already established “event files” lead to a clear influence of subsequent actions. If a stimulus already bound in an “event-file” is presented in a different context, pre-existing connections within the pre-existing “event file” lead to problems, because pre-existing bindings have to be released first. These problems are referred to as “partial repetition costs.” The magnitude of these “partial repetition costs”, which are represented, for example, as increased reaction time or error rate in “stimulus response tasks”, represent a measure of the strength of the link between perception and action. Indeed, initial studies have shown an increase in these “partial repetition costs” in GTS patients as evidence of a particularly strong coupling between percepts (e.g., pre-sensations) and actions (e.g., tics).

Differentiation of GTS from functional tics.

Against the background of the recent strong increase in media portrayal of tic disorders, especially extreme manifestations with very accentuated coprophenomena, and due to the fact that symptoms that have little or nothing in common with a classic Tourette syndrome are also referred to as Tourette, it is important to make a clear distinction between GTS and other disorders. Of particular importance here are the “tic-like movements” that have recently become more frequent and occur in the context of functional disorders. Especially in social media and on video platforms such as YouTube, there is an accumulation of “Tourette patients” who generate enormous media attention by presenting bizarre and, for a special target group, certainly entertaining behaviors. This public display of alleged tics, which is completely untypical for classic Tourette’s patients, causes a strong distortion of the public perception of GTS and thus leads to an enormous burden for actual sufferers and their relatives. A distinction between functional disorders with tic-like movements and classic Tourette syndrome is of extraordinary therapeutic importance. The following points can serve as orientation: If, for example, “tics” are rather complex, slow, tonic, and not, as described above, short, fragmentary, jerky movements, this rather speaks against the presence of a classic GTS. A contextual reference or target- or object-related action also tend to indicate the presence of a functional disorder. Similarly, tics in the context of a GTS are usually not of an immediate communicative nature. This is especially true for the rather rare coprophenomena, which often play a very central role in the media. If the swear words are short, “choppy” and stereotypically repeated without direct reference to a situation or person, this is typical of GTS, whereas, for example, complete sentences, a situational reference by which a specific person might feel offended, or a variety of different expressions that are not or rarely repeated are more indicative of a functional disorder. Purposeful name-calling, purposeful destruction of objects, sexually assaultive behaviors, or attacks on other people are not among the symptoms of Tourette syndrome.

Additional clues may include symptom onset (GTS usually elementary school age, functional tics usually >18), possible comorbidities (GTS often ADHD, anxiety and obsessive-compulsive disorder, functional disorders more often personality disorders), and lack of response to antipsychotics in functional disorders.

Overall, it is therefore important not to see Tourette syndrome as a kind of collective term for socially unacceptable behaviors and to refer patients to a special outpatient clinic in case of doubt in order to avoid a misdiagnosis and the sometimes serious consequences associated with it.

Take-Home Messages

GTS is not a psychosomatic disorder, but rather a neurological or neuro-psychiatric disorder that is predominantly genetically determined and has underlying neuroanatomical and neurophysiological abnormalities.
Often the course is benign, so that no special therapy is required.
Coprolalia occurs in only about 20% of affected individuals and usually consists of single, “choppy” swear words without contextual reference or communicative character.
Effective drug, psychotherapeutic, and interventional therapies are available for significant distress.
The differentiation from functional disorders with “tic-like
movements” can be difficult, so that in case of doubt a presentation in a special outpatient clinic is advisable.

Acknowledgments: We thank the German Research Foundation (DFG) for its support (FOR 2698).