Key points

Introduction

Functional tic-like behaviors (FTLBs) are a phenomenon that gained recent attention during the coronavirus disease 2019 (Covid-19) pandemic when movement disorder clinics noticed a sudden influx of patients with a very atypical course of tic-like movements. This disorder has also been called functional tics, functional tic-like movements, or more recently TikToc tics in the lay press. However, “functional tic-like behaviors” is the current terminology recommended by the European Society for the Study of Tourette Syndrome’s guidelines as they felt this better captures the often complex nature of the sounds and movements observed in this patient population.

FTLBs fall under the more general umbrella of functional neurologic disorders, specifically functional neurologic disorder with motor symptoms. Previously called conversion disorder, functional neurologic disorders are characterized by neurologic symptoms that are not compatible with a known neurologic condition or lesion. While it was previously thought that these symptoms represented a traumatic event that was directly “converted” into subconsciously produced neurologic symptoms, it is not recognized that only about half of the patients have a history of significant psychological trauma and 15% do not have evidence of any psychiatric antecedent such as anxiety or mood disorder. The change in terminology therefore reflects a change in diagnostic criteria: it is no longer necessary to identify an antecedent trauma and instead the focus is on positive findings that are characteristic of functional disorders rather than solely the absence of evidence of other neurologic disorders.

FTLBs take their name from comparison with the tics seen in neurodevelopmental tic disorders that appear in childhood such as Tourette syndrome and chronic motor or chronic vocal tic disorder. These disorders are defined by the presence of tics: brief but repetitive sounds or movements. The sounds and movements straddle the border between voluntary and involuntary movements: most patients will be able to hold their tics off briefly but will find it uncomfortable to do so. For patients with neurodevelopmental tic disorders, most of their tics will be simple tics: simple sounds and movements such as prominent blinking, eye rolling, grimaces, head jerks, sniffs, snorts, and throat clearing. More rarely, individuals will have more complex tics such as purposeful-appearing gestures, words, or phrases.

FTLBs were once considered a rare manifestation of functional neurologic disorder when compared with other functional movement disorders. ^, This changed during the Covid-19, which caused a huge strain on health care systems across the globe. Outside of the influx of critically ill patients requiring care for Covid-19 itself, the fear and isolation experienced worldwide, as countries used quarantine strategies to try to slow the spread, also caused shortages in other areas such as mental health care. These factors likely contributed to an influx of adolescents and young adults presenting with atypical tic-like movements. ^{, ,} Although many of the sounds and movements exhibited by these young people were different compared to what is typically seen in patients with Tourette syndrome, they were strikingly similar to other patients presenting at the same time, despite the fact that the patients were often separated in geographic space. Often referred to as “TikTok tics” in the lay press, patients presented with movements that frequently bore significant similarity to videos of social media influencers who claimed to have Tourette syndrome, although movement disorder experts who reviewed these social media videos saw multiple characteristics that were atypical of known tic disorders. Other patients did not have clear exposure to tic social media, yet nevertheless presented with features atypical of neurodevelopmental tics.

Interestingly, although this is the first time a mass outbreak of functional neurologic disorder across national lines occurred in living memory, it is not the first time functional tics specifically have been a symptom of a mass conversion event. A similar phenomenon on a smaller scale happened 10 years earlier in the small town of Le Roy, New York. ^, In that case, 20 students in Junior-Senior high school, spanning different social groups, developed FTLBs. Like the more recent Tiktok patients, these movements had key differences in comparison to true tics. Also interestingly, social media such as Facebook was cited by some experts as potentially contributing to the spread of symptoms through the student body.

The separation of FTLBs from Tourette syndrome can seem daunting, given that both are clinical diagnoses with similar comorbidities and symptoms that are by their nature paroxysmal, changeable, and suggestible, often with an otherwise normal physiologic exam. However, the increase of cases during the Covid-19 pandemic has given us the benefit of an influx of clinical data that has allowed clear patterns that provide diagnostic clarity to emerge. Although there are no individual features that are completely unique to either neurodevelopmental tic disorders or FTLBs, when taken as a whole, FTLBs have a distinctly different course that can be diagnosed with confidence. ^, Table 1 directly compares the expected features of FTLBs to neurodevelopmental disorders, as it is discussed in detail in the following section.

Clinical presentation

FTLBs are likely to present in adolescents and young adults with sudden, severe symptoms. ^{, , , ,} This is in contrast to neurodevelopmental tic disorders, which generally present prior to age 12 with peak presentation between ages 5 and 9. ^, Although the majority of patients with FTLBs described in the literature did not have tics prior to adolescence, in 1 case series 23% of patients had a prior history of neurodevelopmental tics before developing secondary FTLBs. This is comparable to the significant minority of patients with both epilepsy and functional seizure-like attacks. In patients with both neurodevelopmental tics and new FTLBs, patients may report sudden significant worsening of their symptoms and notice differences such as greater violence or severity of the new sounds and movements and reduced ability to suppress new sounds and movements.

Patients with FTLBs often have more complex sounds and movements and comparatively fewer simple sounds and movements as compared to neurodevelopmental tics. ^, Symptoms also lack the rostro to caudal progression of tics expected in neurodevelopmental tics. ^, Coprolalia and copropraxia at onset are both common, in contrast to neurodevelopmental tics where this is usually something that develops later. ^{, , ,} Self-harming or goal-directed movements such as self-hitting, hitting others, or throwing objects are also common. ^,

If they have previously been incorrectly diagnosed with neurodevelopmental tic disorders, their symptoms will have proven resistant to standard treatment. ^, Some patients may have both preexisting neurodevelopmental tics and FTLBs. These patients may note that their new symptoms are significantly different from their prior ones in terms of suppressibility, severity, and response to treatment.

Etiology

Increased understanding of functional neurologic disorders in general has led to the realization that the causes and predisposing factors for functional neurologic disorders are heterogeneous and best viewed through a biopsychosocial model of the disease. ^, This model views diseases, particularly those that affect mental health, as an interplay of multiple factors. The development of anxiety or depression, for example, is impacted by genetic factors, emotional style/regulation, and social environment. The same has been found to be true for functional neurologic disorders.

From a psychological perspective, the classic view of functional neurologic disorders has been to view them as the conversion of an emotional trauma response into physical symptoms. Trauma, including neglect, sexual abuse, bullying, and abuse experienced as a child does occur at increased rates in patients with functional neurologic disorder and is certainly a predisposing factor. However, 52% of patients with functional neurologic disorders do not have any history of major trauma. These patients may instead report more typical stressors, such as the desire to do well in school or struggles to balance extracurriculars with other expectations. Still others may not report many stressors at all. Anxiety is very common in these patients, occurring in 20% to 50% of patients with all types of functional neurologic disorders and being reported in 60% of patients with FTLBs. ^, Depression is reported in 38% to 95%. It should be noted, however, that in some studies up to 40% of patients with FTLBs do not have anxiety or depression. In patients that do not have these disorders, illness beliefs/expectations are thought to instead play a major role. Beyond these classic illnesses, patients with functional neurologic disorder tend to have atypical emotional regulation. A study on pediatric patients with functional neurologic symptoms found that patients with functional neurologic symptoms tend to either display excessive suppression of or give excessive attention to negative emotions.

It is worth pointing out that biological factors are often treated as distinct from the psychological factors discussed above, but this distinction is somewhat arbitrary as these same psychological factors are rooted in neurobiology. For example, in addition to qualitatively displaying abnormal regulation of their own emotions, patients with functional neurologic disorders have increased activation in the amygdala when discussing stressful life events or when viewing emotionally charged stimuli such as angry faces. In addition to emotional regulation, FMRI and PET studies have revealed differences in activity levels in areas of the brain that are relevant to threat processing, attention, and sense of agency/autonomy. ^, Interestingly, in studies that have looked at patients who have recovered from their symptoms after appropriate treatment, some of these changes seem to normalize. ^,

In addition to classical psychiatric disorders such as anxiety and depression, autism is highly prevalent in patients with functional neurologic disorders in general, and functional symptoms in patient with autism may correlate with sensory perception differences. In one large case series, 25% of patients with FTLBs had autism spectrum disorder. Migraine has likewise been linked to functional neurologic disorders.

Exposure to illness is also a predisposing factor to the development of functional neurologic disorders. For example, while much of this review focuses on the differences between FTLBs and neurodevelopmental tics, the 2 disorders do co-occur. In fact, the rates of FTLBs in young people with neurodevelopmental tics may be higher than that in the general population. This is not unexpected as it occurs in other neurologic conditions. Patients with epilepsy are more likely to have functional seizure-like attacks, and patients with Parkinson disease are more likely to have functional tremor. This can also take the form of personal experience of minor traumas, such as mild concussions, car accidents, or illness that would not be expected to cause neurologic pathology.

Finally, exposure to illness can also occur indirectly. Patients with functional neurologic disorder may, instead of having a personal history of illness, have friends or relatives with chronic disease, a family member in health care, or exposure to media about the disease. This is highly relevant to the surge in FTLBs during 2020 to 2021. First, both infection with the Covid-19 virus and the vaccination against Covid-19 were the illness exposure triggers for some patients with functional neurologic disorder. Even for the many patients without such a direct link to either a viral illness or physical stressor, the Covid-19 pandemic itself was a stressful illness exposure given that it was a novel disease with an incredibly variable level of severity from patient to patient and variable symptomology. Moreover, because of this variability in terms of both severity and symptomology, people were encouraged to be hypervigilant about any new symptoms in an attempt to reduce those with mild symptoms from passing the virus to other, more vulnerable hosts. Hypervigilance is a risk factor for functional neurologic disorders. Besides Covid-19 and the stressors of living under pandemic conditions, exposure to tic media also played a major role in the surge in FTLBs. ^{, ,} Many patients reported viewing influencers on social media who claimed to have neurodevelopmental tic disorders. In these cases, the movements displayed by patients were atypical for neurodevelopmental tics but highly similar to each other and to the tic-like behaviors displayed by the influencers they watched. This is not the first time that social media has been linked to FTLBs: a decade prior to the Covid-19 pandemic, there was an outbreak of FTLBs in a town in Upstate New York. At that time, Facebook was thought to play a role in the spread of symptoms among the affected children.

So how do these risk factors come together to cause functional symptoms in a vulnerable patient? The integrated etiology model attempts to reconcile the often heterogenous risk factors in individual patients into a common pathway in which cortical hyperarousal and misinterpretation of symptoms come together to increase the attention paid to and expectation of future symptoms, which then reinforces the symptoms when they recur. The mechanism is thought to be a complex reflex loop similar to that seen in classical conditioning. Although these symptoms are not consciously produced, like any conditioned response, they can be extinguished, and reducing the catastrophic symptom expectation directly contributes to extinguishing the response.

Epidemiology

The true incidence and prevalence of FTLBs is difficult to assess because of the differences in reporting as well as diagnostic uncertainty. The fact that features such as suggestibility and distractibility, often cardinal features used for definitive positive diagnosis of functional movement disorders, are observed in neurodevelopmental tics adds to the confusion and physician’s uncertainty. Although there are now consensus guidelines for the diagnosis of FTLBs, these guidelines were only published in 2023. Nevertheless, reports from expert centers can help us understand the scope of the problem. The movement disorder clinic at Baylor College of Medicine reported a 60% increase in the percentage of new patients diagnosed with a functional neurologic movement disorder in 2020 as compared to that in 2019 and a 90% increase in their pediatric cohort specifically. In this pandemic cohort, functional tremor and dystonia remained the most common presenting symptoms with only 9% presenting with FTLBs. However, the number of patients with FTLBs in the prepandemic cohort was not reported, making it difficult to assess increases in this disorder specifically. However, in a study of 8 pediatric Tourette centers, the percentage of patients presenting with FTLBs increased significantly across all centers (1%–5% pre pandemic, 20%–35% post pandemic).

FTLBs present most commonly in adolescents and young adults although the age range reported is 8 to 61 years. ^, Importantly, while it can occur in preadolescent children, it is rare. In contrast, Tourette syndrome almost always occurs before adolescence. Age of onset of 12 years or older is one of the major criteria for the diagnosis of FTLBs. FTLBs have been reported more commonly in females than in males in most literature, although this is not universal. There is also some emerging evidence that patients with FTLBs may be more likely to have a transgender or nonbinary gender identity.

Follow-up reports have indicated that these patients have for the most part improved. Additionally, the lay press has reported that rates of FTLBs are decreasing, although this has not yet been published in peer-reviewed literature. In our specialized clinic for patients with functional neurologic disorder, new patients with FTLBs are still presenting, although not as commonly as during the early pandemic. Like many patients with functional neurologic symptom disorder, this is often not the only functional symptom these patients have experienced.

Emerging treatments

The diagnostic process of tic-like movement disorders, like most functional neurologic disorders, has shifted from a diagnosis of exclusions to a rule-in diagnosis. Despite the similarities in clinical presentations between neurodevelopmental tics such as Tourette syndrome, the underlying mechanisms behind both syndromes are different. While neurodevelopmental tics are classified as a movement disorder, tic-like behaviors fall under the umbrella of functional neurologic disorders.

Unlike neurodevelopmental tics, there are no set practice parameters for the treatment of tic-like movement disorders. The prognosis of FTLBs is comparable with that of other functional neurologic symptoms disorders. ^, A recent prospective study reports better outcomes in young people with FTLBs than in adults. Within the pediatric population, diagnostic delay and advanced age predict worse prognosis. Therefore, early diagnosis and treatment is of critical importance to ensure favorable outcomes.

Including family members in the assessment and psychoeducation process has been found to be beneficial. Family members may inadvertently reinforce behaviors by enabling patients, thus reinforcing the sick role or by insisting that the patient is faking which may further worsen symptoms. The initial evaluation should, thus, include a comprehensive evaluation, and the clinician should discuss at length positive signs and provide the patient and family with a better understanding optimizing the acceptance of the diagnosis. An explanation the patient and family understand and accept minimizes seeking unnecessary medical interventions and promotes appropriate treatments. ^, In contrast, a lack of diagnosis can lead to inappropriate interventions that risk serious harm to the patient. For example, in some cases where FTLBs were misdiagnosed as neurodevelopmental tics, patients received multiple trials of pharmacotherapy with no response and were eventually diagnosed with intractable tics and went on to undergo invasive deep brain stimulation surgery. Therefore, recognizing FTLBs early on and explaining the diagnosis to the patient (and to the parents if the patient is a child) are paramount to the treatment process and influence the prognosis. ^{, ,} Depending on the presenting symptoms, the treatment team may involve a neurologist, psychiatrist, psychologist, speech, occupational or physical therapist, and social worker, among others.

The adoption of a multidisciplinary biopsychosocial approach is recommended to identify main stressors and contributing factors including psychiatric comorbidities ^{, ,} and design an individualized treatment plan. ^, Helping the patient identify exacerbating factors and reducing triggers can help minimize symptoms. One such stressor is social media. Studies have shown that more time watching social media was associated with greater tic severity and lower quality of life. Therefore, limiting social media exposure and reducing virtual misinformation would be beneficial. Symptoms are also often reinforced by bringing attention to them and by avoidance of social stressors and obligations as a response to the symptoms. Thus, it is imperative to implement measures that would minimize attention and avoidance/escape behaviors.

Studies investigating treatment of FTLBs are scarce, and to date, there are no randomized controlled studies investigating effective treatments for functional tics. Given the data from patients with other functional neurologic symptoms supporting behavior therapy as first line treatment, the many contributing factors that can impact them such as stress and psychiatric comorbidities, and the lack of data regarding pharmacotherapy, targeting the symptoms with behavior management and psychotherapy seems to be the best approach. Behavioral treatments including comprehensive behavioral intervention for tics (CBIT) and occupational and physical therapy have been found to be helpful, especially when combined with cognitive behavioral therapy techniques used in other functional neurologic disorders. CBIT which combines habit reversal therapy, relaxation training, and psychoeducation addresses the motor symptoms in addition to the underlying stress response. CBIT has proven effective in managing Tourette syndrome and is showing promising results for FTLBs.

Typical pharmacologic treatments used for neurodevelopmental tics have not been found to be effective for functional tics and resulted in significant side effects. ^{, , , , ,} Failed medication trials are occasionally viewed as beneficial in further cementing the functional diagnosis. A study by Cavanna and colleagues revealed that pharmacotherapy was more common in patients with true movement disorders (82%) than in those with FTLBs (49%) and slightly less than 40% received psychotherapy in both groups. ^, In FTLBs, pharmacotherapy primarily aims to regulate emotional state and target co-occurring psychiatric disorders like anxiety and depression (ie, SSRIs). ^{, , , ,} Targeting underlying mood and anxiety has led to an improvement in functional symptoms. Other treatments such as cannabinoid molecules have also shown promise.

Discussion

Prior to the Covid-19 pandemic, FTLB was considered a rare form of functional neurologic disorder. This changed when an increased rate of FTLBs came to the attention of both the medical community and the lay press during the Covid-19 pandemic. ^, While FTLBs were not the only manifestation of the increased rate of functional symptoms seen during the Covid-19 pandemic, they got special attention in part because there was clear evidence of spread among patients who were not in contact with each other via social media alone. ^, While the spread of symptoms via social media has slowed and most of the patients who developed symptoms in the setting of pandemic stressors have recovered significantly, this does not mean that we should consider FTLBs a completely resolved health problem. Patients with FTLBs still present to our clinic although the frequency is greatly reduced. Rather, we should use both the increased rate and increased attention to these symptoms to better recognize and treat future patients.

It has also increased our ability to distinguish between FTLBs and neurodevelopmental tics. This task can seem daunting as features such as suggestibility, an extremely specific positive exam finding in most functional movement disorders, are an expected finding at least to some degree in neurodevelopmental tics. Indeed, one of the things that emerge from the recent literature is that there is no single feature that by itself distinguishes between FTLBs and neurodevelopmental tics. ^{, ,} Many comorbidities, ranging from attention deficit hyperactivity disorder and obsessive-compulsive disorder (OCD) to autism and anxiety, occur in both populations although they may be more common in one than another, nor is the appearance of tics alone enough to allow experts to consistently distinguish between FTLBs and neurodevelopmental tics. While complex tics and coprolalia are more common in patients with FTLBs, they certainly occur in patients with more significant burden of neurodevelopmental tics. Even age of onset, one of the most specific features, cannot distinguish between FTLBs and neurodevelopmental tics, given that there are a small percentage of patients with neurodevelopmental tics that do not develop their symptoms until adolescence and a small percentage of patients with FTLBs who develop their symptoms before adolescence. Further complicating the picture, both neurodevelopmental tic disorders and FTLBs can co-occur in the same patients.

However, although there is no individual feature that distinguishes between these patients with perfect reliability, when looked at as a whole, the clinical picture painted by these patients is distinct from that of patients with neurodevelopmental tics. ^{, ,} Suspicion for FTLBs should be high in patients presenting with new tics after age 11, and this suspicion can be confirmed with the presence of comorbidities and semiology more typical of FTLBs. ^, In terms of semiology, a rapid onset course with continuously worsening, complex movements and sounds with early coprophenomenon and a lack of typical rostral to caudal gradient of symptoms are highly consistent with FTLBs. Comorbidities can be more challenging as the disorders share many comorbidities. OCD is far more common in neurodevelopmental tics. Unsurprisingly, other functional neurologic symptoms are more common in FTLBs. While anxiety and autism are more common in patients with functional tics, physicians must keep in mind that they are fairly common in neurodevelopmental tics as well. ^, Self-injury, trauma, and suicidal ideation increase specificity for FTLBs. ^, The new European Guidelines for the diagnosis of FTLBs provide formal guideline for making the diagnosis ( Table 2 ).

Table 2

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

Genetics of Tourette Syndrome Evidence-Based Assessment of Tourette Syndrome Evidence-Based Behavior Therapy for Tourette Syndrome Pharmacotherapy for Tourette Syndrome Mindfulness-Based Interventions for Tourette Syndrome The Role of CBGTC Synaptic Neurotransmission in the Pathophysiology of Tics

Stay updated, free articles. Join our Telegram channel

Join