What are the Key Phenomenological Clues to Diagnose Functional Tic‐Like Behaviors in the Pandemic Era?

Abstract

Background

Functional tic‐like behaviors (FTLBs) can be difficult to distinguish from tics.

Objectives

To describe the phenomenology of FTLBs in youth and assess the movements and vocalizations most suggestive of the diagnosis.

Methods

We compared the phenomenology of tics between youth (<20 yr) with FTLBs and with primary tics from our Registry in Calgary, Canada.

Results

Two hundred and thirty‐six youths were included: 195 with primary tics (75% males; mean age: 10.8 yr) and 41 with FTLBs (98% females; 16.1 yr). In the bivariate models, FTLBs were most associated with copropraxia (OR = 15.5), saying words (OR = 14.5), coprolalia (OR = 13.1), popping (OR = 11.0), whistling (OR = 9.8), simple head movements (OR = 8.6), and self‐injurious behaviors (OR = 6.9). In the multivariable model, FTLBs were still associated with saying words (OR = 13.5) and simple head movements (OR = 6.3). Only 12.2% of youth with FTLBs had throat clearing tics (OR = 0.2).

Conclusions

This study shall help physicians diagnose youth with FTLBs according to the presence/association of specific movements and vocalizations.

Functional tic‐like behaviors (FTLBs) are a subtype of functional movement disorder, consisting in movements or vocalizations resembling tics. Since the beginning of the SARS‐CoV2 pandemic, there has been a dramatic increase of patients seen with FTLBs in movement disorder clinics throughout the world. ¹ , ² , ³ , ⁴ , ⁵ , ⁶ , ⁷ , ⁸ , ⁹ Before 2020, FTLBs were less commonly reported in the literature. ¹⁰ , ¹¹ , ¹² , ¹³ , ¹⁴ , ¹⁵ The recently published expert consensus on diagnostic criteria can help distinguish FTLBs from Tourette's syndrome (TS), based on major and minor diagnostic criteria. ¹⁶ Major diagnostic criteria include: age at first symptom onset of 12 years or older; rapid onset and evolution of symptoms; and characteristic phenomenology (such as predominance of complex movements/vocalizations, variable reproduction of behaviors, lack of typical rostrocaudal progression). ¹⁶ Minor diagnostic criteria include: specific comorbidity profile with predominant anxiety/depression; and presence of other functional neurological symptoms. ¹⁶ The authors proposed that a clinically definite diagnosis of FTLBs requires the presence of three major criteria, and a clinically probable diagnosis of FTLBs requires the presence of two major and one minor criterion. ¹⁶

Suggested phenomenological characteristics of FTLBs include specific complex movements, such as large‐amplitude or violent arm/hand movements, banging chest/head, hitting others or self, body language, throwing objects, copropraxia, or freezing/motor blocking. ⁵ , ¹⁶ Specific vocal tic‐like behaviors include bizarre words and statements that can be often context‐dependent and coprolalia. ¹⁶ These behaviors can sometimes be seen in patients with TS, and conversely patients with FTLBs can present with only few of these complex behaviors and have other tics that are simple. This phenomenological overlap between tics and FTLBs has often lead to misdiagnosis of FTLBs, before and after the pandemic. ¹⁰ Moreover, many papers have reported that patients can present with both FTLBs and a pre‐existing tic disorder, up to 19% of cases based on an international registry. ¹⁷ Co‐existence of functional neurological disorder and organic pathology is not rare, ¹⁸ and can make the recognition of the functional component harder. ¹⁰

Although the phenomenology of FTLBs has been described in many cohorts since the beginning of the pandemic, there is a need to find clinical and accurate clues to better recognize FTLBs. ¹⁹ Our aim was to describe the phenomenology of FTLBs in youth and assess which movements and vocalizations were most strongly associated with this diagnosis.

Methods

Youth below the age of 20 years old with FTLBs and with primary tic disorders (PTD) have been prospectively included in our Tic Disorders Registries at the Tourette and Pediatric Movement Disorder Clinic at the Alberta Children's Hospital and in the Movement Disorders Clinic at the Foothills Medical Centre in Calgary, Canada. PTD were defined according to the diagnostic criteria of the DSM 5. ²⁰ FTLBs were diagnosed based on primarily age of onset (≥12 yr) and rapid onset over days to weeks.

In this cross‐sectional study, we recorded age at first clinical assessment, age at tic onset, sex, and diagnosis. We described the phenomenology of tics in individuals using the Yale Global Tic Severity Scale (YGTSS), which includes a detailed tic inventory, collected with reference to the past week.

This project received ethical approval from the University of Calgary Conjoint Health Research Ethics Board (REB 16‐1116). Parents (or youth aged 18 or older) provided signed informed consent and children provided assent to study participation and publication of the study results.

A t‐test was used to compare means. Bivariate logistic regression models with odds ratios (OR) and 95% CI were used to quantify the association between each behavior and FTLBs’ diagnosis. After identifying the behaviors that were suggestive of FTLBs, we built a multivariable logistic regression model to assess which features remain associated with FTLBs, while adjusting for age. All statistical analyses were performed using StataCorp. 2021. Stata Statistical Software: Release 17. College Station, TX: StataCorp LLC. A P‐value <0.05 was considered significant for all analyses.

Results

A total of 236 youths were included: 195 (82.6%) with PTD (75% male sex; mean age at evaluation: 10.8 years, range 4–17; 69% with TS, 7% with persistent motor tics, 1% with persistent vocal tics and 6% with provisional tics) and 41 (17.4%) with FTLBs (98% female sex; mean age: 16.1 years, range 11–20).

The most common motor tics in patients with FTLBs were simple head movements (37/41, 90.2%), eye blinking (25/41, 61.0%), simple arm movements (22/41, 53.7%), shoulder shrugs (22/41, 53.7%), self‐injurious behaviors (22/41, 53.7%), simple nose movements (18/41, 43.9%), facial grimace (18/41, 43.9%), simple eye movements (16/41, 39.0%) and copropraxia (15/41, 36.6%). The most common vocal tics in patients with FTLBs were enunciation of words (20/41, 48.8%), coprolalia (18/41, 43.9%), sniffing (15/41, 36.6%), echolalia (13/41, 31.7%) and whistling (11/41, 26.8%).

In the bivariate logistic regression models, the movements and vocalizations which were most associated with FTLBs were: copropraxia (OR = 15.5, 95% CI = 5.8–41.6, P < 0.0001), saying words (OR = 14.5, 95% CI = 6.2–33.9, P < 0.0001), coprolalia (OR = 13.1, 95% CI = 5.5–31.1, P < 0.0001), popping noises (OR = 11.0, 95% CI = 2.6–45.9, P = 0.01), whistling (OR = 9.8, 95% CI = 3.5–27.4, P < 0.0001), simple head movements (OR = 8.6, 95% CI = 3.0–25.1, P < 0.0001), and self‐injurious behaviors (OR 6.9, 95% CI = 3.3–14.4, P < 0.0001). Throat clearing tics were found in only five youths with FTLBs (12.2%) whereas they were the most common vocal tic in patients with PTD (80/195, 41.0%) (OR = 0.2, 95% CI = 0.1–0.5, P = 0.001). Figure 1 and 2 display the prevalence of simple tics and of complex tics in youth with FTLBs and in youth with PTD, and associated OR from the bivariate logistic regression models.

Figure 1.

Prevalence of simple tics by type/localization in youth with functional tic‐like behaviors (pink) and in youth with primary tics (green). Below the graph are the odds ratios (OR) and P‐values when comparing both groups for each tic (logistic regressions). mvts, movements.

Figure 2.

Prevalence of complex tics by type/localization in youth with functional tic‐like behaviors (pink) and in youth with primary tics (green). Below the graph are the odds ratios (OR) and P‐values when comparing both groups for each tic (logistic regressions). Blocking, motor blocking; compulsiv., tic‐related compulsive behaviors; mvts, movements; speech atypic., speech atypicalities.

In the multivariable logistic regression model adjusted for age (pseudo‐R2 = 0.5774), FTLBs were still associated with simple head movements (OR = 6.3, 95% CI = 1.4–29.1, P = 0.019) and enunciation of words (OR = 13.5, 95% CI = 2.6–69.4, P = 0.002). In this model, FTLBs were also associated with age (OR = 1.7, 95% CI = 1.4–2.2, P < 0.0001).

Discussion

In this cross‐sectional study, we found that simple head movements and enunciation of words were the movements and vocalizations that were the most associated with FTLBs in comparison to primary tics.

In our sample, the most common motor FTLBs were simple head movements, eye blinking, simple arm movements, shoulder shrugs and self‐injurious behaviors. In a sample of 203 children and adolescents with TS, the five most common motor tics were simple face and head tics ²¹ ; other cohorts have found shoulder shrugs and arm jerks being very frequent as well. ²² , ²³ Thus, there are no obvious differences in the most frequent motor tics in both disorders, with the exception of self‐injurious behavior being very common in FTLBs. We suspect this is due to the high reporting of any tics by FTLB sufferers, who have overall more numerous tics than people with TS. ¹⁷ This is important to remember because individuals with FTLBs often exhibit many tic‐like behaviors, only a few of which are relevant to suspect the diagnosis.

The most common vocal tics in our patients with FTLBs were enunciation of words, coprolalia, sniffing, echolalia and whistling. This distribution is dominated by complex vocalizations and contrasts with the most common phonic tics seen in patients with TS, being throat clearing, sniffing, grunting, enunciation of syllables, and echolalia. ²¹ , ²² Interestingly, throat clearing tics were significantly inversely associated with FTLBs in our study (OR = 0.20), and therefore more suggestive of PTD.

In TS, the generation and the distribution of tics have been suggested to follow a somatotopic map in the brain. ²⁴ According to this theory, the body regions affected by tics may depend on their cortico‐striatal representations. The presence of this common neural mechanism could explain the consistency of tic phenomenology through the ages. In contrast, etiology of FTLBs has been suggested to come from biological (eg, genetic, altered brain connectivity), social (eg, adverse experiences, environmental stressors), and psychological factors (eg, mental health comorbidities, personality, trauma) that interact within a general biopsychosocial model of pathology. ⁵ , ²⁵ , ²⁶ , ²⁷ , ²⁸ Especially, the exposure to videos on social media displaying individuals with FTLBs have probably led to the reproduction of very peculiar behaviors, that an interesting study described based on 100‐most viewed videos in TikTok under #tourettes² (eg, complex statements, context‐dependent coprolalia, throwing objects, hitting self/others).

When controlling for all behaviors in the multivariable model, we observed that simple head movements, enunciation of words, and age were still associated with the diagnosis of FTLBs. Others behaviors were found suggestive of FTLBs in the bivariate models, including copropraxia, coprolalia, popping noises, whistling, writing tics, motor blocking, echolalia, simple shoulder shrugs, clicking, simple arm and nose movements. A recent video‐based analysis of FTLBs and/or PTD by experts in the field demonstrated that it was difficult to distinguish both based on observation of the movement disorder alone; clinicians also need information about the clinical history (eg, onset, evolution of symptoms, presence of contextual triggers). ¹⁹ However, in this study, the authors did feel that phenomenology was the most important factor in the diagnostic recognition. ¹⁶ , ¹⁹ We suggest that one should be suspicious of FTLBs in the context of one or several of the above‐mentioned behaviors, associated with suggestive factors from the history. Worth emphasizing, the three simple phonic tics on the list, popping noises, whistling and clicking, are uncommon in TS (respectively 2%, 4% and 6%).

A quick recognition of FTLBs versus tics is very important in the clinic, because misdiagnosis of FTLBs can lead to escalation of potentially deleterious treatments. Currently, proposed management of FTLBs includes psychoeducation, behavioral interventions and treatment of mental health comorbidities. ¹⁷ , ²⁵ , ²⁹ , ³⁰ , ³¹

Limitations of our study include its monocentric nature and our inability to build reliable specificity and sensitivity scores testing the power of each tic to predict the diagnosis of FTLBs, possibly due to an overall small number of complex tics, especially phonic. In our sample, some patients with FTLBs had a previous history of tics. It is possible that some of the newly developed behaviors in these patients might have been primary tics that recurred. This might have been the case for newly developed behaviors phenomenologically similar to typical simple tics (eg, eye blinking): as a result, the prevalence of simple behaviors within the repertoire of FTLBs could have been overestimated. The strengths include the comprehensive tic assessment and the rather large cohort of individuals.

In conclusion, our work suggests that, when associated to a late age of onset and a rapid evolution of symptoms, phenomenology is a very important element in distinguishing FTLBs and primary tics. Several characteristic movements and vocalizations are strongly associated with FTLBs and should not be missed in the clinic. Future observations will be useful to evaluate whether and how the phenomenology of FTLBs varies across different populations or throughout historical changes in social perception and representation of tics and tic‐like behaviors.

Author Roles

(1) Research Project: A. Conception, B. Organization, C. Execution; (2) Statistical Analysis: A. Design, B. Execution, C. Review and Critique; (3) Manuscript Preparation: A. Writing of the First Draft, B. Review and Critique.

C.N.: 1A, 1B, 1C, 2A, 2B, 3A, 3B

D.M.: 1A, 1B, 1C, 2A, 2C, 3B

L.B.: 1B, 1C, 3B

J.F.: 1B, 1C, 3B

T.P.: 1A, 1B, 1C, 2A, 2C, 3B

Disclosures

Ethical Compliance Statement: This project received ethical approval from the University of Calgary Conjoint Health Research Ethics Board (REB 16–1116). Parents (or youth aged 18 or older) provided signed informed consent and children provided assent to study participation and publication of the study results. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines.

Funding Sources and Conflicts of Interest: The authors have no conflict of interest to report. Dr Nilles received salary support for this work from the French Gilles de la Tourette Association (AFSGT) and the Owerko Centre of Alberta Children's Hospital Research Institute.

Financial Disclosures for the Previous 12 Months: CN has received salary support from the French Gilles de la Tourette Association (AFSGT) and the Owerko Centre of Alberta Children's Hospital Research Institute. DM has received compensation for consultancies for Sunovion and Merz Pharmaceuticals, honoraria from Dystonia Medical Research Foundation Canada and Merz Pharmaceuticals, royalties from Springer‐Verlag and Oxford University Press, funding grants from: Dystonia Coalition‐RDCN‐NIH plus Dystonia Medical Research Foundation and Dystonia Medical Research Foundation Canada, and National Spasmodic Torticollis Association (NSTA) Sacramento Chapter, The Owerko Foundation, Weston Family Foundation and the Michael P. Smith Family. LB has no disclosures to report. JF has no disclosures to report. TP received research funding from Alberta Health, the Owerko Centre of Alberta Children's Hospital Research Institute, the Mathison Centre for Mental Health Research & Education, and the Public Health Agency of Canada.