Functional tic-like presentations differ strikingly from Provisional Tic Disorder

Amanda L. Arbuckle; Emily C. Bihun; Bradley L. Schlaggar; Kevin J. Black

doi:10.12688/f1000research.129252.1

Home Browse Functional tic-like presentations differ strikingly from Provisional...

ALL Metrics

Views

Downloads

Get PDF

Get XML

Export

▬

✚

Brief Report

Functional tic-like presentations differ strikingly from Provisional Tic Disorder

[version 1; peer review: 1 approved, 1 approved with reservations]

Amanda L. Arbuckle¹, Emily C. Bihun¹, Bradley L. Schlaggar^2-4, Kevin J. Black ^1,5-7

PUBLISHED 22 Dec 2022

Author details Author details

¹ Department of Psychiatry, Washington University in St. Louis, School of Medicine, St. Louis, Missouri, 63110, USA
² Kennedy Krieger Institute, Baltimore, Maryland, 21205, USA
³ Department of Neurology, Johns Hopkins Medicine, Baltimore, Maryland, 21287, USA
⁴ Department of Pediatrics, Johns Hopkins Medicine, Baltimore, MD, 21287, USA
⁵ Department of Neurology, Washington University in St. Louis, School of Medicine, St. Louis, Missouri, 63110, USA
⁶ Department of Radiology, Washington University in St. Louis, School of Medicine, St. Louis, Missouri, 63110, USA
⁷ Department of Neuroscience, Washington University in St. Louis, School of Medicine, St. Louis, Missouri, 63110, USA

Amanda L. Arbuckle
Roles: Data Curation, Formal Analysis, Investigation, Writing – Original Draft Preparation, Writing – Review & Editing

Emily C. Bihun
Roles: Data Curation, Investigation, Writing – Review & Editing

Bradley L. Schlaggar
Roles: Funding Acquisition, Investigation, Writing – Review & Editing

Kevin J. Black
Roles: Conceptualization, Formal Analysis, Funding Acquisition, Project Administration, Software, Supervision, Writing – Original Draft Preparation, Writing – Review & Editing

OPEN PEER REVIEW

REVIEWER STATUS

This article is included in the Tics collection.

Abstract

Background: Recent years have seen a dramatic increase in new “tic” cases in teens and young adults. These individuals often present with fulminant onset of symptoms not commonly seen in Tourette syndrome (TS) and are often diagnosed with Functional Neurological Symptom Disorder (FND-tic). However, some authors have questioned whether this illness truly differs from typical Provisional Tic Disorder (PTD) and TS. Previous studies have compared FND-tic, usually a few months after symptom onset, to patients with TS, usually years after symptom onset. We sought to test whether the presenting symptoms of FND-tic differ substantially from those in patients at a similar duration of symptoms who are later diagnosed with TS.
Methods: This comparative study examines clinical features summarized from published reports of FND-tic with novel data from a longitudinal study of PTD. This study came from a referral center for TS and tic disorders and included 89 children with tics whose first tic occurred a median of 3.6 months earlier, nearly all of whom were diagnosed with a chronic tic disorder at follow-up. Specifically, we examine clinical features identified in a recent literature review as supporting a diagnosis of FND-tic, including symptom characteristics, course, severity and comorbidity.
Results: Several clinical features dramatically distinguish the patients diagnosed with FND-tic from those diagnosed with typical PTD. For example, coprophenomena are reported at or shortly after symptom onset in over half of FND-tic patients, whereas even several months after onset, coprophenomena had occurred in only 1 of 89 children with PTD. Six clinical features each have a positive predictive value over 90% for FND-tic diagnosis if prior probability is 50%.
Conclusions: These new data provide strong evidence supporting the diagnostic validity of FND-tic as distinct from TS.

Keywords

Tic Disorders/classification, Provisional Tic Disorder, Functional Neurological Symptom Disorder, Conversion Disorder, Diagnosis, Differential, Tourette Syndrome

Corresponding author: Kevin J. Black

Competing interests: No competing interests were disclosed.

Grant information: Research reported in this publication was supported by National Institutes of Health, awards K24MH087913 to KJB; R21NS091635 to BLS and KJB; K01MH104592; R01MH104030 to KJB and BLS; the Washington University Institute of Clinical and Translational Sciences grants UL1RR024992 and UL1TR000448; and the Eunice Kennedy Shriver National Institute of Child Health & Human Development of the National Institutes of Health under Award Number U54HD087011 to the Intellectual and Developmental Disabilities Research Center at Washington University. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Copyright: © 2022 Arbuckle AL et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

How to cite: Arbuckle AL, Bihun EC, Schlaggar BL and Black KJ. Functional tic-like presentations differ strikingly from Provisional Tic Disorder [version 1; peer review: 1 approved, 1 approved with reservations]. F1000Research 2022, 11:1566 (https://doi.org/10.12688/f1000research.129252.1) First published: 22 Dec 2022, 11:1566 (https://doi.org/10.12688/f1000research.129252.1) Latest published: 17 Apr 2023, 11:1566 (https://doi.org/10.12688/f1000research.129252.2)

Introduction

Recent years have seen a dramatic increase in new “tic” cases in teens and young adults.¹^,² These individuals often present with fulminant onset of symptoms not commonly seen in Tourette syndrome (TS), but often similar to those found in videos tagged as “Tourette” on social media.³ For instance, echopraxia and coprolalia occur in more than half of these individuals at symptom onset.³ The nature and characteristics of these symptoms, and the onset age and course of illness have led experienced clinicians to differentiate these cases from TS and to diagnose instead Functional Neurological Symptom Disorder (FND). FND with tic-like symptoms (hereinafter “FND-tic”) has been reported previously, but prior to 2019 was considered rare, occurring in < 2% of tic or tic-like cases at five major referral centers from three continents.⁴

Some experts have expressed skepticism as to whether a new diagnosis (FND) is needed for these patients, positing that the previous understanding of TS may have been too narrow.⁵ Perhaps, for instance, echopraxia is present early in the course of TS much more often than has been recognized. We concur with these authors that clearly differentiating a new diagnosis from existing diagnoses is a key component of diagnostic validity.⁶ Substantial published data describe typical clinical features of chronic tic disorders, but almost no prospective data have been published on symptoms in the first year after tic onset.⁷^,⁸ This evidence gap is crucial because most FND-tic patients at clinical centers have had symptoms for only a few months (mean 0.4 years in one study⁴). Here, we directly address this concern by providing for the first time substantial data on relevant clinical features during the first few months after symptom onset in children ultimately diagnosed with TS.

Methods

The New Tics study is a prospective, longitudinal study that enrolled 89 children ages 5–10 years whose first tic occurred in the past 9 months (median 3.6 months).⁹ Children are assessed using multiple informants (child, parent, trained interviewer, and observation by an experienced clinician for more than an hour, including by video while the child is alone). The diagnosis in this situation is Provisional Tic Disorder (PTD), and nearly all these children (77 of 79) were diagnosed with TS (70) or a persistent tic disorder (7) when they returned at the one-year anniversary of their first tic.¹⁰ Here we report the prevalence and timing from the New Tics sample of various features that occur commonly in FND-tic patients.

The feature list was drawn from a recent review of FND-tic, a narrative review that included all primary data publications on FND-tic known to its authors as of August, 2022.³ The comparison data for FND-tic patients comes from 26 published reports, with pertinent data in 17 reports⁴^,¹¹^–²⁶ describing a total of 336 patients (data file available as Underlying data²⁷). For quantitative variables, the weighted mean is provided (weighted by N in each report), along with the median and range of the summary values reported in each relevant publication.

Most of these features thought to suggest FND-tic were recorded prospectively in the New Tics study, including age, sex, premonitory urges, tic suppression, coprophenomena, and family history. However, since the New Tics sample was enrolled almost entirely before the recent FND-tic upsurge, some of these clinical features were recorded indirectly. For instance, to match “severe symptoms at onset,” defined differently in various reports on FND-tic, we conservatively chose from the New Tics sample all patients with emergency department visits or disability prior to the screening visit, or a high score on the Yale Global Tic Severity Scale’s²⁸ impairment item at screening. Details on other such choices are given in footnotes to Table 1.

Table 1. Comparison of various clinical features in FND-tic and in typical PTD.^a

FND, Functional Neurological Symptom Disorder; FND-tic, Functional Neurological Symptom Disorder with tic-like symptoms; PTD, Provisional Tic Disorder; NP, number of publications; OCD, obsessive compulsive disorder; ADHD, attention deficit hyperactivity disorder; YGTSS, Yale Global Tic Severity Scale.

Feature	FND NP ^b	FND numerator/denominator (percentage)	FND median percentage (range)	New Tics ^c number (percentage)
Sex (% female)	17	251/336 (75)	72 (20–100)	25 (28)
Typical tic disorder diagnosis prior to current episode onset	11	33/150 (22)	15 (0–100)	21/125 (17) ^d
Sudden, abrupt onset	10 ^e	136/142 (96)	100 (77–100)	15/75 (20) ^f or 46/62 (74) ^g
Symptoms in extremities before face and neck	7	43/100 (43)	40 (15–100)	10 (11)
Coprophenomena at onset	8	68/115 (59)	54 (0–77)	1 (1)
Tics involving the body or limbs without a history of tics involving the eyes, face, and head	7	29/84 (35)	18 (0–77)	10 (11)
Premonitory urges present	9	56/118 (48)	60 (0–100)	85 (96)
Severe symptoms at onset	6	82/172 (48)	77 (30–100)	3–5 (3–6)
Extreme “attacks” of tic-like behavior	4	44/68 (65)	82 (36–100)	0–2 (0–2)
Inability to suppress	10	74/120 (62)	70 (0–100)	20 (22)
Tic-like phenomena are constant in severity over time rather than waxing and waning	5	50/75 (67)	68 (15–100)	51 (58)
Movements or vocalizations that are dramatically worse in the presence of others versus when alone	3	15/32 (47)	50 (11–100)	0 (0) ^h
Symptoms that dramatically and persistently disrupt the person’s intended actions or communications	3	34/52 (65)	39 (36–89)	2 (2)
Family history of tics	9	17/131 (13)	0 (0–60)	30 (34)
Family history of OCD	1	1/22 (5)	5	14 (16)
Family history of ADHD	1	6/22 (27)	27	25 (28)
ADHD diagnosis before/at presentation	9	69/216 (32)	22 (0–48)	39 (43)
OCD diagnosis before/at presentation	8	11/127 (9)	6 (0–23)	27 (30)
Anxiety disorder prior to/at presentation	8	77/132 (58)	53 (11–100)	27 (30)

Feature	FND NP	FND weighted mean	FND median (range)	New Tics mean
Age of onset	15	22.3	16.5 (7.5–53.6)	7.6
Age at presentation	5	20.5	18.8 (11.2–36.3)	7.9
YGTSSⁱ Total Tic Score (0-50)	2	32.7	32.4 (31.5–33.3)	16.9
YGTSS Impairment (0-50)	2	30.2	31.2 (28.6–33.8)	7.6
YGTSS Global Severity Score (0-100)	3	62.8	62.6 (61.9–65.3)	24.3

a Specified clinical features in patients with tic-like symptoms (“FND”) from the articles reviewed in Malaty et al. (2022),³ compared to participants with typical Provisional Tic Disorder from the New Tics study (“New Tics”).

b NP = number of publications from the table in Malaty et al. (2022)³ that contributed data to the statistics in this row.

c N = 89 except where numerator and denominator are provided.

d N = 125, the number of participants who came for a screening visit after reporting recent onset of tics during initial telephone contact. Some were found during careful screening to have a prior episode of transient tics.

e Excludes the two reports that defined the sample by sudden onset.⁴^,²¹

f The investigator assigned the most likely symptom onset date within a date range (possible onset dates) of less than 7 days.

g From parents’ answers as to whether the onset of the first tic was sudden or gradual.

h Investigator noted tics during the history and exam (approximately 45 minutes), but no tics when observing the child alone in the room via video camera (approximately 40 minutes).

i Yale Global Tic Severity Scale.

Data analysis

Fisher’s exact test was used to find the probability of differences in frequency of features between the two populations (fisher_exact from SciPy (RRID:SCR_008058) 1.9.1).²⁹

Ethical considerations

The New Tics study was approved by the Washington University Human Research Protection Office (IRB, protocol numbers 201109157 and 201707059), all participants assented to participation, and a parent or other legal guardian provided written documentation of informed consent.

Results

Stark differences in presentation distinguish the FND-tic patients from typical PTD (Table 1). For example, coprophenomena are reported at or shortly after symptom onset in 59% of FND-tic patients. By contrast, coprophenomena had occurred in only 1 of 89 children with PTD at an average of 3.6 months after tic onset. Similarly, the TS International Database Consortium found that only 2% of TS patients in tertiary centers retrospectively reported coprophenomena at symptom onset, and only 20% ever manifested coprophenomena by an average of 5 years after tic onset.³⁰ Movements or vocalizations that were dramatically worse in the presence of others versus when alone occurred in 47% of FND-tic patients, but in none of the New Tics PTD sample. Symptoms dramatically and persistently disrupted intended actions in 65% of FND-tic patients, but in only 2% of PTD. The prevalence of prolonged tic attacks was 65% in FND-tic, but 0–2% in PTD. Other features that differed substantially include lack of premonitory urges (53% vs. 4%) and severe symptoms at onset (48% vs. 3–6%). Table 1 and Table 2 provide details on these comparisons and include statistics on a dozen more clinical features of FND-tic that differ from the New Tics PTD sample.

In a patient with recent onset of tics, the presence of any one of the features named above raises the probability of a non-TS diagnosis from 50% (as when the clinician is ambivalent about the diagnosis prior to considering this feature) to over 90% (Table 2). Other features differ significantly but are less useful diagnostically. For instance, obsessive compulsive disorder (OCD) is more than three times less common in FND-tic than in PTD (p<.0001), but its absence only raises the probability of FND-tic from 50% to 57%.

Table 2. Diagnostic utility of the binary features in Table 1.^a

PPV, positive predictive value; NPV, negative predictive value; OCD, obsessive compulsive disorder; ADHD, attention deficit hyperactivity disorder; TS, Tourette syndrome; FND, Functional Neurological Symptom Disorder.

Feature	p ^b	PPV (NPV)	prior 2%	prior 50%
Movements or vocalizations that are dramatically worse in the presence of others versus when alone	.000	PPV =	100%	100%
Coprophenomena at onset	.000	PPV =	52%	98%
Coprolalia at presentation	.000	PPV =	47%	98%
Symptoms that dramatically and persistently disrupt the person’s intended actions or communications	.000	PPV =	38%	97%
Extreme “attacks” of tic-like behavior	.000	PPV =	38%	97%
Premonitory urges present	.000	NPV =	19%	92%
Severe symptoms at onset (defined variously in different studies)	.000	PPV =	15%	89%
Sudden, abrupt onset (NewTics: onset confidence window < 7 days)	.000	PPV =	9%	83%
Symptoms in extremities before face and neck	.000	PPV =	7%	79%
Tics involving the body or limbs without a history of tics involving the eyes, face, and head	.000	PPV =	6%	75%
Inability to suppress	.000	PPV =	5%	73%
Female	.000	PPV =	5%	73%
Anxiety disorder prior to/at presentation	.000	PPV =	4%	66%
Family history of tics	.000	NPV =	3%	57%
OCD diagnosis before/at presentation	.000	NPV =	3%	57%
Typical tic disorder diagnosis prior to current episode onset	.185	PPV =	3%	57%
Sudden, abrupt onset (NewTics: per parent tic survey)	.000	PPV =	3%	56%
ADHD diagnosis before/at presentation	.050	NPV =	2%	54%
Tic-like phenomena are constant in severity over time rather than waxing and waning	.164	PPV =	2%	53%
Family history of OCD	.152	NPV =	2%	53%
Family history of ADHD	.584	NPV =	2%	50%

a PPV of a non-TS diagnosis for the binary features in Table 1, assuming a prior probability for FND of 2% (typical pre-pandemic prevalence at a referral center⁴) or 50% (representing clinical equipoise about a given patient’s diagnosis before considering this feature). NPV is shown for features more common in typical TS, equivalent to PPV for the absence of the given feature.

b Fisher’s exact test; “.000” means < .0005; p values bolded if p < .05/20 = .0025.

Note: Values for PPV and NPV are bolded if ≥67%.

Discussion

We demonstrate conclusively that patients with functional tic-like symptoms differ notably from typical tic patients at the same stage of the disorder, namely in the first few months after symptom onset. Previous reports have compared FND-tic to TS,³^,³¹ but not to a large PTD sample. The older age of the FND-tic group could be seen as a limitation of our study, since one might posit different symptoms at different ages of tic onset might be part of the natural history of tic disorder. However, this theoretical concern does not in fact limit our conclusions, because retrospective studies of TS and a prospective study of PTD in siblings of TS probands all found peak tic onset before age 10 years old in both sexes; adult onset of tics is uncommon.⁷^,⁸^,³²

The data presented here do not prove the etiology of the tic-like symptoms diagnosed in the cited reports; hence the limited claim that these symptoms represent a different illness than PTD/TS. However, the marked difference in presentation these data demonstrate is an important argument adduced in the cited reports to support the diagnosis of functional neurological symptom disorder. Diagnosing FND-tic is important, since to the extent of our current knowledge, its prognosis and optimal treatment differ from those of TS.³

In conclusion, these new clinical data about the first few months after tic onset prior to diagnosis of TS provide strong evidence supporting the diagnostic validity of functional tic-like symptoms as distinct from PTD and TS.

Data availability

Underlying data

Information on ‘The New Tics Study: A Novel Approach to Pathophysiology and Cause of Tic Disorders’ can be found at NIMH Data Archive and NIH RePORTER (Project Number 1R01MH104030-01A1).

Open Science Framework: Supplemental materials for publication: Functional tic-like presentations differ strikingly from Provisional Tic Disorder. https://doi.org/10.17605/OSF.IO/RSFXN ²⁷.

This project contains the following underlying data:

- FNS_vs_TS.csv (summary table from the FND-tic publications cited by Malaty et al.³)
- FND-tic_not_PTD.py (python script used to summarize data for Tables 1 and 2)

Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).

Acknowledgements

An earlier version of this article can be found on Open Science Framework (doi: https://doi.org/10.31219/osf.io/3u6bk).

References

1. Anderson KN, Radhakrishnan L, Lane RI, et al.: Changes and inequities in adult mental health-related emergency department visits during the COVID-19 pandemic in the US. JAMA Psychiatry. 2022 May 1; 79(5): 475–485. PubMed Abstract | Publisher Full Text | Free Full Text
2. Radhakrishnan L, Leeb RT, Bitsko RH, et al.: Pediatric emergency department visits associated with mental health conditions before and during the COVID-19 pandemic - United States, January 2019-January 2022. MMWR Morb. Mortal. Wkly Rep. 2022 Feb 25; 71(8): 319–324. Epub 20220225. PubMed Abstract | Publisher Full Text
3. Malaty IC, Anderson S, Bennett S, et al.: Diagnosis and management of functional tic-like phenomena. J. Clin. Med. 2022; 11: 6470. PubMed Abstract | Publisher Full Text | Free Full Text
4. Pringsheim T, Ganos C, McGuire JF, et al.: Rapid onset functional tic-like behaviors in young females during the COVID-19 pandemic. Mov. Disord. 2021 Dec; 36(12): 2707–2713. Epub 20210831. PubMed Abstract | Publisher Full Text | Free Full Text
5. Conelea CA, Bervoets J, Davies EB, et al.: A call for caution: 'stop that' sentiments threaten tic research, healthcare and advocacy. Brain. 2022 May 24; 145(4): e18–e20. PubMed Abstract | Publisher Full Text
6. Robins E, Guze SB: Establishment of diagnostic validity in psychiatric illness: its application to schizophrenia. Am. J. Psychiatry. 1970; 126: 983–987. Publisher Full Text
7. Black KJ, Black ER, Greene DJ, et al.: Provisional Tic Disorder: What to tell parents when their child first starts ticcing [version 1]. F1000Res. 2016; 5: 696. PubMed Abstract | Publisher Full Text | Free Full Text
8. Openneer TJC, Huyser C, Martino D, et al.: Clinical precursors of tics: an EMTICS study. J. Child Psychol. Psychiatry. 2022 Mar; 63(3): 305–314. Epub 20210625. PubMed Abstract | Publisher Full Text | Free Full Text
9. Black KJ, Kim S, Schlaggar BL, et al.: The New Tics study: A novel approach to pathophysiology and cause of tic disorders. J. Psychiatr. Brain Sci. 2020; 5: e200012. Epub 2020/06/27. PubMed Abstract | Publisher Full Text | Free Full Text
10. Kim S, Greene DJ, Bihun EC, et al.: Provisional Tic Disorder is not so transient. Sci. Rep. 2019 Mar 8; 9(1): 3951. Epub 2019/03/10. PubMed Abstract | Publisher Full Text | Free Full Text
11. Baizabal-Carvallo JF, Jankovic J: The clinical features of psychogenic movement disorders resembling tics. J. Neurol. Neurosurg. Psychiatry. 2014 May; 85(5): 573–575. Epub 20131120. PubMed Abstract | Publisher Full Text
12. Buts S, Duncan M, Owen T, et al.: Paediatric tic-like presentations during the COVID-19 pandemic. Arch. Dis. Child. 2022 Mar; 107(3): e17. Epub 20211125. PubMed Abstract | Publisher Full Text
13. Dooley JM, Stokes A, Gordon KE: Pseudo-tics in Tourette syndrome. J. Child Neurol. 1994 Jan; 9(1): 50–51. PubMed Abstract | Publisher Full Text
14. Ganos C, Edwards MJ, Müller-Vahl K: "I swear it is Tourette's!": On functional coprolalia and other tic-like vocalizations. Psychiatry Res. 2016 Dec 30; 246: 821–826. Epub 20161017. PubMed Abstract | Publisher Full Text
15. Heintz CE, van Tricht MJ , van der Salm SM , et al.: Neuropsychological profile of psychogenic jerky movement disorders: importance of evaluating non-credible cognitive performance and psychopathology. J. Neurol. Neurosurg. Psychiatry. 2013 Aug; 84(8): 862–867. Epub 20130216. PubMed Abstract | Publisher Full Text
16. Larsh TR, Wu SW, Gilbert DL: Comparison of impairment in functional tic disorders versus Tourette syndrome. Pediatr. Neurol. 2022 Sep; 134: 83–84. Epub 20220628. PubMed Abstract | Publisher Full Text
17. Mink JW: Conversion disorder and mass psychogenic illness in child neurology. Ann. N. Y. Acad. Sci. 2013 Nov; 1304: 40–44. Epub 20131018. PubMed Abstract | Publisher Full Text
18. Monday K, Jankovic J: Psychogenic myoclonus. Neurology. 1993; 43(2): 349–352. Publisher Full Text
19. Robinson S, Hedderly T: Novel psychological formulation and treatment of "tic attacks" in Tourette syndrome. Front. Pediatr. 2016; 4: 46. Epub 20160511. PubMed Abstract | Publisher Full Text | Free Full Text
20. Hull M, Parnes M: Tics and TikTok: Functional Tics Spread Through Social Media. Mov. Disord Clin. Pract. 2021 Nov; 8(8): 1248–1252. Epub 20210701. PubMed Abstract | Publisher Full Text | Free Full Text
21. Pringsheim T, Martino D: Rapid onset of functional tic-like behaviours in young adults during the COVID-19 pandemic. Eur. J. Neurol. 2021 Nov; 28(11): 3805–3808. Epub 20210804. PubMed Abstract | Publisher Full Text | Free Full Text
22. Demartini B, Ricciardi L, Parees I, et al.: A positive diagnosis of functional (psychogenic) tics. Eur. J. Neurol. 2015 Mar; 22(3): 527–e36. Epub 20141209. PubMed Abstract | Publisher Full Text
23. Han VX, Kozlowska K, Kothur K, et al.: Rapid onset functional tic-like behaviours in children and adolescents during COVID-19: Clinical features, assessment and biopsychosocial treatment approach. J. Paediatr. Child Health. 2022 Jul; 58(7): 1181–1187. Epub 20220305. PubMed Abstract | Publisher Full Text | Free Full Text
24. Janik P, Milanowski Ł, Szejko N: Psychogenic tics: clinical characteristics and prevalence. Psychiatr. Pol. 2014 Jul-Aug; 48(4): 835–845. Tiki psychogenne: charakterystyka kliniczna i czestość wystepowania. PubMed Abstract
25. Olvera C, Stebbins GT, Goetz CG, et al.: TikTok tics: A pandemic within a pandemic. Mov. Disord. Clin. Pract. 2021; 8(8): 1200–1205. PubMed Abstract | Publisher Full Text | Free Full Text
26. Paulus T, Bäumer T, Verrel J, et al.: Pandemic tic-like behaviors following social media consumption. Mov. Disord. 2021 Dec; 36(12): 2932–2935. Epub 20210924. PubMed Abstract | Publisher Full Text
27. Black KJ, Arbuckle A:Supplemental Materials for Publication: Functional Tic-like Presentations Differ Strikingly from Provisional Tic Disorder. [Dataset]. OSF. Dec 2022. Publisher Full Text
28. Leckman JF, Riddle MA, Hardin MT, et al.: The Yale Global Tic Severity Scale: Initial testing of a clinical-rated scale of tic severity. J. Am. Acad. Child Adolesc. Psychiatry. 1989; 28(4): 566–573. PubMed Abstract | Publisher Full Text
29. Virtanen P, Gommers R, Oliphant TE, et al.: SciPy 1.0: Fundamental algorithms for scientific computing in Python. Nat. Methods. 2020 Mar; 17(3): 261–272. Epub 20200203. PubMed Abstract | Publisher Full Text | Free Full Text
30. Freeman RD, Zinner SH, Müller-Vahl KR, et al.: Coprophenomena in Tourette syndrome. Dev. Med. Child Neurol. 2009 Mar; 51(3): 218–227. Epub 20081204. PubMed Abstract | Publisher Full Text
31. Nilles C, Martino D, Berg L, et al.: Can the phenomenology of functional tic-like behaviours be sufficient to make the diagnosis? AACAP/CACAP annual meeting; 19 Oct 2022; Toronto, Ontario, Canada.2022.
32. Black KJ, Kim S, Yang NY, et al.: Course of tic disorders over the lifespan. Curr. Dev. Disord. Rep. 2021 Jun; 8(2): 121–132. Epub 2021/06/29. PubMed Abstract | Publisher Full Text | Free Full Text

Comments on this article Comments (0)

Version 2

VERSION 2 PUBLISHED 22 Dec 2022

Author details Author details

Amanda L. Arbuckle
Roles: Data Curation, Formal Analysis, Investigation, Writing – Original Draft Preparation, Writing – Review & Editing

Emily C. Bihun
Roles: Data Curation, Investigation, Writing – Review & Editing

Bradley L. Schlaggar
Roles: Funding Acquisition, Investigation, Writing – Review & Editing

Kevin J. Black
Roles: Conceptualization, Formal Analysis, Funding Acquisition, Project Administration, Software, Supervision, Writing – Original Draft Preparation, Writing – Review & Editing

Competing interests

No competing interests were disclosed.

Grant information

Research reported in this publication was supported by National Institutes of Health, awards K24MH087913 to KJB; R21NS091635 to BLS and KJB; K01MH104592; R01MH104030 to KJB and BLS; the Washington University Institute of Clinical and Translational Sciences grants UL1RR024992 and UL1TR000448; and the Eunice Kennedy Shriver National Institute of Child Health & Human Development of the National Institutes of Health under Award Number U54HD087011 to the Intellectual and Developmental Disabilities Research Center at Washington University. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Article Versions (2)

version 2

Revised

Published: 17 Apr 2023, 11:1566

https://doi.org/10.12688/f1000research.129252.2

version 1

Published: 22 Dec 2022, 11:1566

https://doi.org/10.12688/f1000research.129252.1

© 2022 Arbuckle AL et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Download

Export To

metrics

	Views	Downloads
F1000Research	-	-
PubMed Central Data from PMC are received and updated monthly.	-	-

Citations

SEE MORE DETAILS

CITE

how to cite this article

Arbuckle AL, Bihun EC, Schlaggar BL and Black KJ. Functional tic-like presentations differ strikingly from Provisional Tic Disorder [version 1; peer review: 1 approved, 1 approved with reservations]. F1000Research 2022, 11:1566 (https://doi.org/10.12688/f1000research.129252.1)

NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article.

track

receive updates on this article

Track an article to receive email alerts on any updates to this article.

Open Peer Review

Version 1

VERSION 1

PUBLISHED 22 Dec 2022

Views

Reviewer Report 31 Mar 2023

Tammy Hedderly, Paediatric Neurology Department, Evelina London Children’s Hospital, King's College London, Guy’s & St Thomas’ NHS Foundation Trust, London, England, UK

Approved

https://doi.org/10.5256/f1000research.141921.r158571

The authors, all highly experienced 'Tourettologists', have approached this topic in an interesting and novel manner to try and provide some evidence for the ability to differentiate functional tic like behaviours from those seen in provisional tic disorders, usually related to Tourettes at follow up. This is a complex area, with some researchers proposing some shared mechanisms and overlapping neurobiology in the presentations. This paper uses some usefully collected detailed (although some retrospective) clinical data of children with PTD within a few months of presentation to compare characteristics demonstrating some useful distinguishing features. The presentation of the statistics could benefit from a little more expansion and explanation, especially for the non-expert, as it seems an important aspect of this paper. For example, table 2 is not that clearly explained and could do with more detail.

There are some limitations, but these have been clearly highlighted by the authors, such as the difference in ages of the two groups. I therefore would support this paper as it represents a useful contribution to the ongoing exploration of the functional tic-like phenomenon. I do wonder whether the dichotomy of subjects is a problem and would welcome wider discussions by the authors, on the situations seen commonly in the clinic in which young people, demonstrate both Tourette-related tics and functional tic-like behaviours together. This paper raised a question in my mind, as to whether the authors could have included distinguishing factors for the concept of provisional or transient functional disorder, especially when appearing in the context of exposure to social media or influencers.

Thank you for an interesting contribution.

Is the work clearly and accurately presented and does it cite the current literature?

Yes
Is the study design appropriate and is the work technically sound?

Yes
Are sufficient details of methods and analysis provided to allow replication by others?

Yes
If applicable, is the statistical analysis and its interpretation appropriate?

Partly
Are all the source data underlying the results available to ensure full reproducibility?

Yes
Are the conclusions drawn adequately supported by the results?

Partly

Competing Interests: No competing interests were disclosed.

Reviewer Expertise: Paediatric Neurology , Movement Disorders and Tourettes

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

CITE

Report a concern

Author Response (F1000Research Advisory Board Member) 17 Apr 2023

Kevin J Black, Department of Psychiatry, Washington University in St. Louis, School of Medicine, St. Louis, 63110, USA

17 Apr 2023

Author Response F1000Research Advisory Board Member

We thank Dr. Hedderly for her thoughtful and expert critique. Below we respond to each comment in turn.

1. The presentation of the statistics could benefit from a little ... Continue reading We thank Dr. Hedderly for her thoughtful and expert critique. Below we respond to each comment in turn.

1. The presentation of the statistics could benefit from a little more expansion and explanation, especially for the non-expert, as it seems an important aspect of this paper. For example, table 2 is not that clearly explained and could do with more detail.

Thank you. We agree. The new text in 'Results' reads as follows:

"Table 2 illustrates the clinical value of these comparisons, viewing each clinical feature as a “test” for FND-tic, with its associated sensitivity and specificity. We also provide the positive predictive value (PPV) for each feature thought to indicate FND-tic. The PPV represents how confident one can be of a FND-tic diagnosis given the presence of the listed feature. The PPV depends on the prior probability of the FND-tic diagnosis, or its likelihood before one knows whether a given patient has that feature. We provide PPV for each feature based on two prior probabilities, 2% and 50%. The first, 2%, represents the approximate rate before the pandemic of functional tic-like symptoms at clinical referral centers. 4 Clinical equipoise about a given participant’s diagnosis is represented by a prior probability of 50%, for instance if one knows that a referring clinician is ambivalent about whether the patient has PTD or FND-tic, but one has not yet read the chart nor seen the patient. Features thought to be less common in FND-tic are listed with a negative predictive value (NPV), equivalent to PPV for the absence of the given feature."

2. I do wonder whether the dichotomy of subjects is a problem and would welcome wider discussions by the authors, on the situations seen commonly in the clinic in which young people, demonstrate both Tourette-related tics and functional tic-like behaviours together.

We agree the discussion did not address this issue previously. The discussion now includes this additional paragraph:

"We note that 22% of the patients reported in the FND-tic papers in fact had a prior history of typical tics, and many of them exhibited both tics and functional tic-like symptoms at the time they presented due to the latter. We have structured our results around whether FND-tic can be diagnosed, not whether PTD can also be diagnosed. In other words, when a patient presents with a typical history for TS but also new symptoms, the features above would allow more confidence in diagnosing FND-tic in addition to TS."

3. This paper raised a question in my mind, as to whether the authors could have included distinguishing factors for the concept of provisional or transient functional disorder, especially when appearing in the context of exposure to social media or influencers.

The reviewer raises a very interesting question that appears to include two concepts: diagnostic utility of exposure to social media and nosology.

a) The exposure to social media or other examples that the new symptoms appear to recapitulate is an important diagnostic clue. We and others have discussed that issue elsewhere (e.g. Frey et al. (2022) and Malaty et al. (2022)). Unfortunately, we have no prospectively collected data on this question from the PTD group. Anecdotally, I can report that although over a third of our New Tics study participants had a parent or sibling with tics, only once or twice was there any suggestion that the child's first tic may have appeared to be prompted by the family member's similar tic. We have added to the discussion the following paragraph:

"Other features in addition to those studied here may also be important for diagnosis. For instance, exposure to tic-like symptoms on social media was a common feature discussed in the papers discussing FND-tic in the past few years. 3 Unfortunately, we have no prospectively collected data from the PTD group on exposure to others with similar symptoms."

b) Traditionally, functional neurological symptoms have not been diagnosed differently based on duration of the defining symptoms. The closest analogy I can think of is Briquet's syndrome (and its dramatically modified descendants such as DSM-IV somatization disorder), which required not only atypical, medically unexplained symptoms starting before midlife but also numerous symptoms over time, affecting a variety of organ systems. Personally I would not favor creating a new diagnosis to represent "presumed functional symptoms in the first year since onset".
We thank Dr. Hedderly for her thoughtful and expert critique. Below we respond to each comment in turn.

1. The presentation of the statistics could benefit from a little more expansion and explanation, especially for the non-expert, as it seems an important aspect of this paper. For example, table 2 is not that clearly explained and could do with more detail.

Thank you. We agree. The new text in 'Results' reads as follows:

"Table 2 illustrates the clinical value of these comparisons, viewing each clinical feature as a “test” for FND-tic, with its associated sensitivity and specificity. We also provide the positive predictive value (PPV) for each feature thought to indicate FND-tic. The PPV represents how confident one can be of a FND-tic diagnosis given the presence of the listed feature. The PPV depends on the prior probability of the FND-tic diagnosis, or its likelihood before one knows whether a given patient has that feature. We provide PPV for each feature based on two prior probabilities, 2% and 50%. The first, 2%, represents the approximate rate before the pandemic of functional tic-like symptoms at clinical referral centers. 4 Clinical equipoise about a given participant’s diagnosis is represented by a prior probability of 50%, for instance if one knows that a referring clinician is ambivalent about whether the patient has PTD or FND-tic, but one has not yet read the chart nor seen the patient. Features thought to be less common in FND-tic are listed with a negative predictive value (NPV), equivalent to PPV for the absence of the given feature."

2. I do wonder whether the dichotomy of subjects is a problem and would welcome wider discussions by the authors, on the situations seen commonly in the clinic in which young people, demonstrate both Tourette-related tics and functional tic-like behaviours together.

We agree the discussion did not address this issue previously. The discussion now includes this additional paragraph:

"We note that 22% of the patients reported in the FND-tic papers in fact had a prior history of typical tics, and many of them exhibited both tics and functional tic-like symptoms at the time they presented due to the latter. We have structured our results around whether FND-tic can be diagnosed, not whether PTD can also be diagnosed. In other words, when a patient presents with a typical history for TS but also new symptoms, the features above would allow more confidence in diagnosing FND-tic in addition to TS."

3. This paper raised a question in my mind, as to whether the authors could have included distinguishing factors for the concept of provisional or transient functional disorder, especially when appearing in the context of exposure to social media or influencers.

The reviewer raises a very interesting question that appears to include two concepts: diagnostic utility of exposure to social media and nosology.

a) The exposure to social media or other examples that the new symptoms appear to recapitulate is an important diagnostic clue. We and others have discussed that issue elsewhere (e.g. Frey et al. (2022) and Malaty et al. (2022)). Unfortunately, we have no prospectively collected data on this question from the PTD group. Anecdotally, I can report that although over a third of our New Tics study participants had a parent or sibling with tics, only once or twice was there any suggestion that the child's first tic may have appeared to be prompted by the family member's similar tic. We have added to the discussion the following paragraph:

"Other features in addition to those studied here may also be important for diagnosis. For instance, exposure to tic-like symptoms on social media was a common feature discussed in the papers discussing FND-tic in the past few years. 3 Unfortunately, we have no prospectively collected data from the PTD group on exposure to others with similar symptoms."

b) Traditionally, functional neurological symptoms have not been diagnosed differently based on duration of the defining symptoms. The closest analogy I can think of is Briquet's syndrome (and its dramatically modified descendants such as DSM-IV somatization disorder), which required not only atypical, medically unexplained symptoms starting before midlife but also numerous symptoms over time, affecting a variety of organ systems. Personally I would not favor creating a new diagnosis to represent "presumed functional symptoms in the first year since onset".
Competing Interests: No competing interests were disclosed. Close
Report a concern
Respond or Comment

COMMENTS ON THIS REPORT

Author Response (F1000Research Advisory Board Member) 17 Apr 2023

Kevin J Black, Department of Psychiatry, Washington University in St. Louis, School of Medicine, St. Louis, 63110, USA

17 Apr 2023

Author Response F1000Research Advisory Board Member

We thank Dr. Hedderly for her thoughtful and expert critique. Below we respond to each comment in turn.

1. The presentation of the statistics could benefit from a little ... Continue reading We thank Dr. Hedderly for her thoughtful and expert critique. Below we respond to each comment in turn.

1. The presentation of the statistics could benefit from a little more expansion and explanation, especially for the non-expert, as it seems an important aspect of this paper. For example, table 2 is not that clearly explained and could do with more detail.

Thank you. We agree. The new text in 'Results' reads as follows:

"Table 2 illustrates the clinical value of these comparisons, viewing each clinical feature as a “test” for FND-tic, with its associated sensitivity and specificity. We also provide the positive predictive value (PPV) for each feature thought to indicate FND-tic. The PPV represents how confident one can be of a FND-tic diagnosis given the presence of the listed feature. The PPV depends on the prior probability of the FND-tic diagnosis, or its likelihood before one knows whether a given patient has that feature. We provide PPV for each feature based on two prior probabilities, 2% and 50%. The first, 2%, represents the approximate rate before the pandemic of functional tic-like symptoms at clinical referral centers. 4 Clinical equipoise about a given participant’s diagnosis is represented by a prior probability of 50%, for instance if one knows that a referring clinician is ambivalent about whether the patient has PTD or FND-tic, but one has not yet read the chart nor seen the patient. Features thought to be less common in FND-tic are listed with a negative predictive value (NPV), equivalent to PPV for the absence of the given feature."

2. I do wonder whether the dichotomy of subjects is a problem and would welcome wider discussions by the authors, on the situations seen commonly in the clinic in which young people, demonstrate both Tourette-related tics and functional tic-like behaviours together.

We agree the discussion did not address this issue previously. The discussion now includes this additional paragraph:

"We note that 22% of the patients reported in the FND-tic papers in fact had a prior history of typical tics, and many of them exhibited both tics and functional tic-like symptoms at the time they presented due to the latter. We have structured our results around whether FND-tic can be diagnosed, not whether PTD can also be diagnosed. In other words, when a patient presents with a typical history for TS but also new symptoms, the features above would allow more confidence in diagnosing FND-tic in addition to TS."

3. This paper raised a question in my mind, as to whether the authors could have included distinguishing factors for the concept of provisional or transient functional disorder, especially when appearing in the context of exposure to social media or influencers.

The reviewer raises a very interesting question that appears to include two concepts: diagnostic utility of exposure to social media and nosology.

a) The exposure to social media or other examples that the new symptoms appear to recapitulate is an important diagnostic clue. We and others have discussed that issue elsewhere (e.g. Frey et al. (2022) and Malaty et al. (2022)). Unfortunately, we have no prospectively collected data on this question from the PTD group. Anecdotally, I can report that although over a third of our New Tics study participants had a parent or sibling with tics, only once or twice was there any suggestion that the child's first tic may have appeared to be prompted by the family member's similar tic. We have added to the discussion the following paragraph:

"Other features in addition to those studied here may also be important for diagnosis. For instance, exposure to tic-like symptoms on social media was a common feature discussed in the papers discussing FND-tic in the past few years. 3 Unfortunately, we have no prospectively collected data from the PTD group on exposure to others with similar symptoms."

b) Traditionally, functional neurological symptoms have not been diagnosed differently based on duration of the defining symptoms. The closest analogy I can think of is Briquet's syndrome (and its dramatically modified descendants such as DSM-IV somatization disorder), which required not only atypical, medically unexplained symptoms starting before midlife but also numerous symptoms over time, affecting a variety of organ systems. Personally I would not favor creating a new diagnosis to represent "presumed functional symptoms in the first year since onset".
We thank Dr. Hedderly for her thoughtful and expert critique. Below we respond to each comment in turn.

1. The presentation of the statistics could benefit from a little more expansion and explanation, especially for the non-expert, as it seems an important aspect of this paper. For example, table 2 is not that clearly explained and could do with more detail.

Thank you. We agree. The new text in 'Results' reads as follows:

"Table 2 illustrates the clinical value of these comparisons, viewing each clinical feature as a “test” for FND-tic, with its associated sensitivity and specificity. We also provide the positive predictive value (PPV) for each feature thought to indicate FND-tic. The PPV represents how confident one can be of a FND-tic diagnosis given the presence of the listed feature. The PPV depends on the prior probability of the FND-tic diagnosis, or its likelihood before one knows whether a given patient has that feature. We provide PPV for each feature based on two prior probabilities, 2% and 50%. The first, 2%, represents the approximate rate before the pandemic of functional tic-like symptoms at clinical referral centers. 4 Clinical equipoise about a given participant’s diagnosis is represented by a prior probability of 50%, for instance if one knows that a referring clinician is ambivalent about whether the patient has PTD or FND-tic, but one has not yet read the chart nor seen the patient. Features thought to be less common in FND-tic are listed with a negative predictive value (NPV), equivalent to PPV for the absence of the given feature."

2. I do wonder whether the dichotomy of subjects is a problem and would welcome wider discussions by the authors, on the situations seen commonly in the clinic in which young people, demonstrate both Tourette-related tics and functional tic-like behaviours together.

We agree the discussion did not address this issue previously. The discussion now includes this additional paragraph:

"We note that 22% of the patients reported in the FND-tic papers in fact had a prior history of typical tics, and many of them exhibited both tics and functional tic-like symptoms at the time they presented due to the latter. We have structured our results around whether FND-tic can be diagnosed, not whether PTD can also be diagnosed. In other words, when a patient presents with a typical history for TS but also new symptoms, the features above would allow more confidence in diagnosing FND-tic in addition to TS."

3. This paper raised a question in my mind, as to whether the authors could have included distinguishing factors for the concept of provisional or transient functional disorder, especially when appearing in the context of exposure to social media or influencers.

The reviewer raises a very interesting question that appears to include two concepts: diagnostic utility of exposure to social media and nosology.

a) The exposure to social media or other examples that the new symptoms appear to recapitulate is an important diagnostic clue. We and others have discussed that issue elsewhere (e.g. Frey et al. (2022) and Malaty et al. (2022)). Unfortunately, we have no prospectively collected data on this question from the PTD group. Anecdotally, I can report that although over a third of our New Tics study participants had a parent or sibling with tics, only once or twice was there any suggestion that the child's first tic may have appeared to be prompted by the family member's similar tic. We have added to the discussion the following paragraph:

"Other features in addition to those studied here may also be important for diagnosis. For instance, exposure to tic-like symptoms on social media was a common feature discussed in the papers discussing FND-tic in the past few years. 3 Unfortunately, we have no prospectively collected data from the PTD group on exposure to others with similar symptoms."

b) Traditionally, functional neurological symptoms have not been diagnosed differently based on duration of the defining symptoms. The closest analogy I can think of is Briquet's syndrome (and its dramatically modified descendants such as DSM-IV somatization disorder), which required not only atypical, medically unexplained symptoms starting before midlife but also numerous symptoms over time, affecting a variety of organ systems. Personally I would not favor creating a new diagnosis to represent "presumed functional symptoms in the first year since onset".
Competing Interests: No competing interests were disclosed. Close
Report a concern

Views

Reviewer Report 25 Jan 2023

Michael Bloch, Department of Psychiatry, Yale School of Medicine, New Haven, Connecticut, USA

Approved with Reservations

https://doi.org/10.5256/f1000research.141921.r158573

This manuscript compares the clinical characteristics of the sample of patients with Functional Neurological Disorder (FND) described in the literature, with a well-characterized sample of Provisional Tic Disorder. Strengths of the manuscript include the clinical importance and novelty of the data as well as the expertise of the authors and the well-written manuscript. Overall, I think this is a manuscript worthy of indexing, although I have several critiques that could potentially improve the manuscript with revision.

I do not believe the primary limitation of the manuscript is really acknowledged in the current draft. Mainly that the FND cases are drawn from the existing literature (where there is likely a large degree of reporting bias) versus a Provisional Tic Disorder sample that is much more general. Basically, there is quite a strong possibility that there are other characteristics associated with group difference other than diagnosis.
Please consider providing statistical tests in table 1 as well as sensitivity, specificity in table 2.
I think in the conclusion the authors should discuss the importance of testing the potentially meaningful differentiators in an independent dataset.
It would also be very worthwhile in further studies to use individual participant data to determine the PPV of multiple predictors to engage in a diagnostic distinction.
If possible, a histogram exploring age and gender differences between the two groups would be helpful.

Is the work clearly and accurately presented and does it cite the current literature?

Yes
Is the study design appropriate and is the work technically sound?

Yes
Are sufficient details of methods and analysis provided to allow replication by others?

Yes
If applicable, is the statistical analysis and its interpretation appropriate?

Yes
Are all the source data underlying the results available to ensure full reproducibility?

Yes
Are the conclusions drawn adequately supported by the results?

Partly

Competing Interests: No competing interests were disclosed.

Reviewer Expertise: Meta-analysis, psychopharmacology, tic disorders, OCD

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

CITE

Report a concern

Author Response (F1000Research Advisory Board Member) 17 Apr 2023

Kevin J Black, Department of Psychiatry, Washington University in St. Louis, School of Medicine, St. Louis, 63110, USA

17 Apr 2023

Author Response F1000Research Advisory Board Member

We thank Dr. Bloch for his thoughtful and expert critique. Below we respond to each comment in turn.

1. I do not believe the primary limitation of the manuscript ... Continue reading We thank Dr. Bloch for his thoughtful and expert critique. Below we respond to each comment in turn.

1. I do not believe the primary limitation of the manuscript is really acknowledged in the current draft. Mainly that the FND cases are drawn from the existing literature (where there is likely a large degree of reporting bias) versus a Provisional Tic Disorder sample that is much more general. Basically, there is quite a strong possibility that there are other characteristics associated with group difference other than diagnosis.

We agree and have edited the ms. to reflect this point. However, the disparity is smaller than one might think. Here is our new text in the discussion:

"The primary concern with the validity of these conclusions arises from the different potential sources of ascertainment bias in the two groups. Fortunately, these differences may not be as problematic as one might suppose. The FND-tic group is older, and if one’s information were limited to this study alone, one might posit that the natural history of tic disorder included different early symptoms at different ages of tic onset. However, the literature includes decades of previous clinical information on typical tic disorders. Retrospective studies of TS and a prospective study of PTD in siblings of TS probands all found peak tic onset before age 10 years old; adult onset of tics is quite uncommon. 7 , 8 , 33 The PTD cases were volunteers willing to participate in a rather intensive research study, and were ascertained by a variety of methods (advertising and referrals from clinicians being the most common) rather than by clinical care-seeking. However, at the screening visit for the study, over 60% of them had sought clinical care for the tics or were planning to. The two FND-tic reports from Calgary, Alberta (child and young adult) were from a prospective registry of all patients seen for tics at their center, which is the only specialty center in their region. FND-tic cases were defined by “rapid onset of complex tic-like behaviors, with escalation to peak severity within hours to days.” In other words, these reports are selected only for being seen at a specialty center for tic-like phenomena. Yet their clinical features are similar to those of the FND-tic literature overall (or even more different from the PTD group). For instance, 95% of the Calgary FND-tic child patients were of female sex, only 25% had ADHD, and only 5% had OCD. We can conclude that potential bias from selecting more interesting, severe or classic cases for published case series does not substantially alter our results. Perhaps most importantly, there are no larger published sources for data about FND-tic nor about PTD. Nevertheless, ideally the results presented here should be confirmed in a new, independent sample."

2. Please consider providing statistical tests in table 1 as well as sensitivity, specificity in table 2.

Done.

3. I think in the conclusion the authors should discuss the importance of testing the potentially meaningful differentiators in an independent dataset.

We agree. The discussion now includes: "ideally the results presented here should be confirmed in a new, independent sample."

4. It would also be very worthwhile in further studies to use individual participant data to determine the PPV of multiple predictors to engage in a diagnostic distinction.

That's an excellent idea. We have supplied individual participant data for the New Tics group as a supplementary file.

5. If possible, a histogram exploring age and gender differences between the two groups would be helpful.

We do not have individual participant data for the FND-tic group (which came from 17 different publications), so we can't do this.
We thank Dr. Bloch for his thoughtful and expert critique. Below we respond to each comment in turn.

1. I do not believe the primary limitation of the manuscript is really acknowledged in the current draft. Mainly that the FND cases are drawn from the existing literature (where there is likely a large degree of reporting bias) versus a Provisional Tic Disorder sample that is much more general. Basically, there is quite a strong possibility that there are other characteristics associated with group difference other than diagnosis.

We agree and have edited the ms. to reflect this point. However, the disparity is smaller than one might think. Here is our new text in the discussion:

"The primary concern with the validity of these conclusions arises from the different potential sources of ascertainment bias in the two groups. Fortunately, these differences may not be as problematic as one might suppose. The FND-tic group is older, and if one’s information were limited to this study alone, one might posit that the natural history of tic disorder included different early symptoms at different ages of tic onset. However, the literature includes decades of previous clinical information on typical tic disorders. Retrospective studies of TS and a prospective study of PTD in siblings of TS probands all found peak tic onset before age 10 years old; adult onset of tics is quite uncommon. 7 , 8 , 33 The PTD cases were volunteers willing to participate in a rather intensive research study, and were ascertained by a variety of methods (advertising and referrals from clinicians being the most common) rather than by clinical care-seeking. However, at the screening visit for the study, over 60% of them had sought clinical care for the tics or were planning to. The two FND-tic reports from Calgary, Alberta (child and young adult) were from a prospective registry of all patients seen for tics at their center, which is the only specialty center in their region. FND-tic cases were defined by “rapid onset of complex tic-like behaviors, with escalation to peak severity within hours to days.” In other words, these reports are selected only for being seen at a specialty center for tic-like phenomena. Yet their clinical features are similar to those of the FND-tic literature overall (or even more different from the PTD group). For instance, 95% of the Calgary FND-tic child patients were of female sex, only 25% had ADHD, and only 5% had OCD. We can conclude that potential bias from selecting more interesting, severe or classic cases for published case series does not substantially alter our results. Perhaps most importantly, there are no larger published sources for data about FND-tic nor about PTD. Nevertheless, ideally the results presented here should be confirmed in a new, independent sample."

2. Please consider providing statistical tests in table 1 as well as sensitivity, specificity in table 2.

Done.

3. I think in the conclusion the authors should discuss the importance of testing the potentially meaningful differentiators in an independent dataset.

We agree. The discussion now includes: "ideally the results presented here should be confirmed in a new, independent sample."

4. It would also be very worthwhile in further studies to use individual participant data to determine the PPV of multiple predictors to engage in a diagnostic distinction.

That's an excellent idea. We have supplied individual participant data for the New Tics group as a supplementary file.

5. If possible, a histogram exploring age and gender differences between the two groups would be helpful.

We do not have individual participant data for the FND-tic group (which came from 17 different publications), so we can't do this.
Competing Interests: No competing interests were disclosed. Close
Report a concern
Respond or Comment

COMMENTS ON THIS REPORT

Author Response (F1000Research Advisory Board Member) 17 Apr 2023

Kevin J Black, Department of Psychiatry, Washington University in St. Louis, School of Medicine, St. Louis, 63110, USA

17 Apr 2023

Author Response F1000Research Advisory Board Member

We thank Dr. Bloch for his thoughtful and expert critique. Below we respond to each comment in turn.

1. I do not believe the primary limitation of the manuscript ... Continue reading We thank Dr. Bloch for his thoughtful and expert critique. Below we respond to each comment in turn.

1. I do not believe the primary limitation of the manuscript is really acknowledged in the current draft. Mainly that the FND cases are drawn from the existing literature (where there is likely a large degree of reporting bias) versus a Provisional Tic Disorder sample that is much more general. Basically, there is quite a strong possibility that there are other characteristics associated with group difference other than diagnosis.

We agree and have edited the ms. to reflect this point. However, the disparity is smaller than one might think. Here is our new text in the discussion:

"The primary concern with the validity of these conclusions arises from the different potential sources of ascertainment bias in the two groups. Fortunately, these differences may not be as problematic as one might suppose. The FND-tic group is older, and if one’s information were limited to this study alone, one might posit that the natural history of tic disorder included different early symptoms at different ages of tic onset. However, the literature includes decades of previous clinical information on typical tic disorders. Retrospective studies of TS and a prospective study of PTD in siblings of TS probands all found peak tic onset before age 10 years old; adult onset of tics is quite uncommon. 7 , 8 , 33 The PTD cases were volunteers willing to participate in a rather intensive research study, and were ascertained by a variety of methods (advertising and referrals from clinicians being the most common) rather than by clinical care-seeking. However, at the screening visit for the study, over 60% of them had sought clinical care for the tics or were planning to. The two FND-tic reports from Calgary, Alberta (child and young adult) were from a prospective registry of all patients seen for tics at their center, which is the only specialty center in their region. FND-tic cases were defined by “rapid onset of complex tic-like behaviors, with escalation to peak severity within hours to days.” In other words, these reports are selected only for being seen at a specialty center for tic-like phenomena. Yet their clinical features are similar to those of the FND-tic literature overall (or even more different from the PTD group). For instance, 95% of the Calgary FND-tic child patients were of female sex, only 25% had ADHD, and only 5% had OCD. We can conclude that potential bias from selecting more interesting, severe or classic cases for published case series does not substantially alter our results. Perhaps most importantly, there are no larger published sources for data about FND-tic nor about PTD. Nevertheless, ideally the results presented here should be confirmed in a new, independent sample."

2. Please consider providing statistical tests in table 1 as well as sensitivity, specificity in table 2.

Done.

3. I think in the conclusion the authors should discuss the importance of testing the potentially meaningful differentiators in an independent dataset.

We agree. The discussion now includes: "ideally the results presented here should be confirmed in a new, independent sample."

4. It would also be very worthwhile in further studies to use individual participant data to determine the PPV of multiple predictors to engage in a diagnostic distinction.

That's an excellent idea. We have supplied individual participant data for the New Tics group as a supplementary file.

5. If possible, a histogram exploring age and gender differences between the two groups would be helpful.

We do not have individual participant data for the FND-tic group (which came from 17 different publications), so we can't do this.
We thank Dr. Bloch for his thoughtful and expert critique. Below we respond to each comment in turn.

1. I do not believe the primary limitation of the manuscript is really acknowledged in the current draft. Mainly that the FND cases are drawn from the existing literature (where there is likely a large degree of reporting bias) versus a Provisional Tic Disorder sample that is much more general. Basically, there is quite a strong possibility that there are other characteristics associated with group difference other than diagnosis.

We agree and have edited the ms. to reflect this point. However, the disparity is smaller than one might think. Here is our new text in the discussion:

"The primary concern with the validity of these conclusions arises from the different potential sources of ascertainment bias in the two groups. Fortunately, these differences may not be as problematic as one might suppose. The FND-tic group is older, and if one’s information were limited to this study alone, one might posit that the natural history of tic disorder included different early symptoms at different ages of tic onset. However, the literature includes decades of previous clinical information on typical tic disorders. Retrospective studies of TS and a prospective study of PTD in siblings of TS probands all found peak tic onset before age 10 years old; adult onset of tics is quite uncommon. 7 , 8 , 33 The PTD cases were volunteers willing to participate in a rather intensive research study, and were ascertained by a variety of methods (advertising and referrals from clinicians being the most common) rather than by clinical care-seeking. However, at the screening visit for the study, over 60% of them had sought clinical care for the tics or were planning to. The two FND-tic reports from Calgary, Alberta (child and young adult) were from a prospective registry of all patients seen for tics at their center, which is the only specialty center in their region. FND-tic cases were defined by “rapid onset of complex tic-like behaviors, with escalation to peak severity within hours to days.” In other words, these reports are selected only for being seen at a specialty center for tic-like phenomena. Yet their clinical features are similar to those of the FND-tic literature overall (or even more different from the PTD group). For instance, 95% of the Calgary FND-tic child patients were of female sex, only 25% had ADHD, and only 5% had OCD. We can conclude that potential bias from selecting more interesting, severe or classic cases for published case series does not substantially alter our results. Perhaps most importantly, there are no larger published sources for data about FND-tic nor about PTD. Nevertheless, ideally the results presented here should be confirmed in a new, independent sample."

2. Please consider providing statistical tests in table 1 as well as sensitivity, specificity in table 2.

Done.

3. I think in the conclusion the authors should discuss the importance of testing the potentially meaningful differentiators in an independent dataset.

We agree. The discussion now includes: "ideally the results presented here should be confirmed in a new, independent sample."

4. It would also be very worthwhile in further studies to use individual participant data to determine the PPV of multiple predictors to engage in a diagnostic distinction.

That's an excellent idea. We have supplied individual participant data for the New Tics group as a supplementary file.

5. If possible, a histogram exploring age and gender differences between the two groups would be helpful.

We do not have individual participant data for the FND-tic group (which came from 17 different publications), so we can't do this.
Competing Interests: No competing interests were disclosed. Close
Report a concern

Comments on this article Comments (0)

Version 2

VERSION 2 PUBLISHED 22 Dec 2022

Open Peer Review

Reviewer Status

Reviewer Reports

	Invited Reviewers
	1	2
Version 2 (revision) 17 Apr 23	read	read
Version 1 22 Dec 22	read	read

Michael Bloch, Yale School of Medicine, New Haven, USA
Tammy Hedderly, King's College London, Guy’s & St Thomas’ NHS Foundation Trust, London, UK

Comments on this article

All Comments(0)

Add a comment

Browse by related subjects

Back to all reports

Reviewer Report

4 Views

15 May 2023 | for Version 2

Michael Bloch, Department of Psychiatry, Yale School of Medicine, New Haven, Connecticut, USA

4 Views Cite this report Responses(0)

Approved

The authors have responded adequately to my critiques. I appreciate this important contribution to the study of tic disorders.

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

Meta-analysis, psychopharmacology, tic disorders, OCD

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

Respond to this report

Responses (0)

Back to all reports

Reviewer Report

3 Views

18 Apr 2023 | for Version 2

Tammy Hedderly, Paediatric Neurology Department, Evelina London Children’s Hospital, King's College London, Guy’s & St Thomas’ NHS Foundation Trust, London, England, UK

3 Views Cite this report Responses(0)

Approved

Thank you to the authors for their response to all my queries and for the clarification. I would like to approve this article as a helpful addition to this field.

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

Paediatric Neurology , Movement Disorders and Tourettes

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

Respond to this report

Responses (0)

Back to all reports

Reviewer Report

18 Views

31 Mar 2023 | for Version 1

Tammy Hedderly, Paediatric Neurology Department, Evelina London Children’s Hospital, King's College London, Guy’s & St Thomas’ NHS Foundation Trust, London, England, UK

18 Views Cite this report Responses(1)

Approved

Is the work clearly and accurately presented and does it cite the current literature?

Yes
Is the study design appropriate and is the work technically sound?

Yes
Are sufficient details of methods and analysis provided to allow replication by others?

Yes
If applicable, is the statistical analysis and its interpretation appropriate?

Partly
Are all the source data underlying the results available to ensure full reproducibility?

Yes
Are the conclusions drawn adequately supported by the results?

Partly

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

Paediatric Neurology , Movement Disorders and Tourettes

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

Respond to this report

Responses (1)

Author Response F1000Research Advisory Board Member

17 Apr 2023

Kevin J Black, Department of Psychiatry, Washington University in St. Louis, School of Medicine, St. Louis, 63110, USA

We thank Dr. Hedderly for her thoughtful and expert critique. Below we respond to each comment in turn.

1. The presentation of the statistics could benefit from a little more expansion and explanation, especially for the non-expert, as it seems an important aspect of this paper. For example, table 2 is not that clearly explained and could do with more detail.

Thank you. We agree. The new text in 'Results' reads as follows:

"Table 2 illustrates the clinical value of these comparisons, viewing each clinical feature as a “test” for FND-tic, with its associated sensitivity and specificity. We also provide the positive predictive value (PPV) for each feature thought to indicate FND-tic. The PPV represents how confident one can be of a FND-tic diagnosis given the presence of the listed feature. The PPV depends on the prior probability of the FND-tic diagnosis, or its likelihood before one knows whether a given patient has that feature. We provide PPV for each feature based on two prior probabilities, 2% and 50%. The first, 2%, represents the approximate rate before the pandemic of functional tic-like symptoms at clinical referral centers. 4 Clinical equipoise about a given participant’s diagnosis is represented by a prior probability of 50%, for instance if one knows that a referring clinician is ambivalent about whether the patient has PTD or FND-tic, but one has not yet read the chart nor seen the patient. Features thought to be less common in FND-tic are listed with a negative predictive value (NPV), equivalent to PPV for the absence of the given feature."

2. I do wonder whether the dichotomy of subjects is a problem and would welcome wider discussions by the authors, on the situations seen commonly in the clinic in which young people, demonstrate both Tourette-related tics and functional tic-like behaviours together.

We agree the discussion did not address this issue previously. The discussion now includes this additional paragraph:

"We note that 22% of the patients reported in the FND-tic papers in fact had a prior history of typical tics, and many of them exhibited both tics and functional tic-like symptoms at the time they presented due to the latter. We have structured our results around whether FND-tic can be diagnosed, not whether PTD can also be diagnosed. In other words, when a patient presents with a typical history for TS but also new symptoms, the features above would allow more confidence in diagnosing FND-tic in addition to TS."

3. This paper raised a question in my mind, as to whether the authors could have included distinguishing factors for the concept of provisional or transient functional disorder, especially when appearing in the context of exposure to social media or influencers.

The reviewer raises a very interesting question that appears to include two concepts: diagnostic utility of exposure to social media and nosology.

a) The exposure to social media or other examples that the new symptoms appear to recapitulate is an important diagnostic clue. We and others have discussed that issue elsewhere (e.g. Frey et al. (2022) and Malaty et al. (2022)). Unfortunately, we have no prospectively collected data on this question from the PTD group. Anecdotally, I can report that although over a third of our New Tics study participants had a parent or sibling with tics, only once or twice was there any suggestion that the child's first tic may have appeared to be prompted by the family member's similar tic. We have added to the discussion the following paragraph:

"Other features in addition to those studied here may also be important for diagnosis. For instance, exposure to tic-like symptoms on social media was a common feature discussed in the papers discussing FND-tic in the past few years. 3 Unfortunately, we have no prospectively collected data from the PTD group on exposure to others with similar symptoms."

b) Traditionally, functional neurological symptoms have not been diagnosed differently based on duration of the defining symptoms. The closest analogy I can think of is Briquet's syndrome (and its dramatically modified descendants such as DSM-IV somatization disorder), which required not only atypical, medically unexplained symptoms starting before midlife but also numerous symptoms over time, affecting a variety of organ systems. Personally I would not favor creating a new diagnosis to represent "presumed functional symptoms in the first year since onset".

View more View less

Competing Interests

No competing interests were disclosed.

Back to all reports

Reviewer Report

24 Views

25 Jan 2023 | for Version 1

Michael Bloch, Department of Psychiatry, Yale School of Medicine, New Haven, Connecticut, USA

24 Views Cite this report Responses(1)

Approved With Reservations

I do not believe the primary limitation of the manuscript is really acknowledged in the current draft. Mainly that the FND cases are drawn from the existing literature (where there is likely a large degree of reporting bias) versus a Provisional Tic Disorder sample that is much more general. Basically, there is quite a strong possibility that there are other characteristics associated with group difference other than diagnosis.
Please consider providing statistical tests in table 1 as well as sensitivity, specificity in table 2.
I think in the conclusion the authors should discuss the importance of testing the potentially meaningful differentiators in an independent dataset.
It would also be very worthwhile in further studies to use individual participant data to determine the PPV of multiple predictors to engage in a diagnostic distinction.
If possible, a histogram exploring age and gender differences between the two groups would be helpful.

Is the work clearly and accurately presented and does it cite the current literature?

Yes
Is the study design appropriate and is the work technically sound?

Yes
Are sufficient details of methods and analysis provided to allow replication by others?

Yes
If applicable, is the statistical analysis and its interpretation appropriate?

Yes
Are all the source data underlying the results available to ensure full reproducibility?

Yes
Are the conclusions drawn adequately supported by the results?

Partly

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

Meta-analysis, psychopharmacology, tic disorders, OCD

Respond to this report

Responses (1)

Author Response F1000Research Advisory Board Member

17 Apr 2023

Kevin J Black, Department of Psychiatry, Washington University in St. Louis, School of Medicine, St. Louis, 63110, USA

We thank Dr. Bloch for his thoughtful and expert critique. Below we respond to each comment in turn.

1. I do not believe the primary limitation of the manuscript is really acknowledged in the current draft. Mainly that the FND cases are drawn from the existing literature (where there is likely a large degree of reporting bias) versus a Provisional Tic Disorder sample that is much more general. Basically, there is quite a strong possibility that there are other characteristics associated with group difference other than diagnosis.

We agree and have edited the ms. to reflect this point. However, the disparity is smaller than one might think. Here is our new text in the discussion:

"The primary concern with the validity of these conclusions arises from the different potential sources of ascertainment bias in the two groups. Fortunately, these differences may not be as problematic as one might suppose. The FND-tic group is older, and if one’s information were limited to this study alone, one might posit that the natural history of tic disorder included different early symptoms at different ages of tic onset. However, the literature includes decades of previous clinical information on typical tic disorders. Retrospective studies of TS and a prospective study of PTD in siblings of TS probands all found peak tic onset before age 10 years old; adult onset of tics is quite uncommon. 7 , 8 , 33 The PTD cases were volunteers willing to participate in a rather intensive research study, and were ascertained by a variety of methods (advertising and referrals from clinicians being the most common) rather than by clinical care-seeking. However, at the screening visit for the study, over 60% of them had sought clinical care for the tics or were planning to. The two FND-tic reports from Calgary, Alberta (child and young adult) were from a prospective registry of all patients seen for tics at their center, which is the only specialty center in their region. FND-tic cases were defined by “rapid onset of complex tic-like behaviors, with escalation to peak severity within hours to days.” In other words, these reports are selected only for being seen at a specialty center for tic-like phenomena. Yet their clinical features are similar to those of the FND-tic literature overall (or even more different from the PTD group). For instance, 95% of the Calgary FND-tic child patients were of female sex, only 25% had ADHD, and only 5% had OCD. We can conclude that potential bias from selecting more interesting, severe or classic cases for published case series does not substantially alter our results. Perhaps most importantly, there are no larger published sources for data about FND-tic nor about PTD. Nevertheless, ideally the results presented here should be confirmed in a new, independent sample."

2. Please consider providing statistical tests in table 1 as well as sensitivity, specificity in table 2.

Done.

3. I think in the conclusion the authors should discuss the importance of testing the potentially meaningful differentiators in an independent dataset.

We agree. The discussion now includes: "ideally the results presented here should be confirmed in a new, independent sample."

4. It would also be very worthwhile in further studies to use individual participant data to determine the PPV of multiple predictors to engage in a diagnostic distinction.

That's an excellent idea. We have supplied individual participant data for the New Tics group as a supplementary file.

5. If possible, a histogram exploring age and gender differences between the two groups would be helpful.

We do not have individual participant data for the FND-tic group (which came from 17 different publications), so we can't do this.

View more View less

Competing Interests

No competing interests were disclosed.

Alongside their report, reviewers assign a status to the article:

Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested

Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.

Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions

[1] 1. Anderson KN, Radhakrishnan L, Lane RI, et al.: Changes and inequities in adult mental health-related emergency department visits during the COVID-19 pandemic in the US. JAMA Psychiatry. 2022 May 1; 79(5): 475–485. PubMed Abstract | Publisher Full Text | Free Full Text

[2] 2. Radhakrishnan L, Leeb RT, Bitsko RH, et al.: Pediatric emergency department visits associated with mental health conditions before and during the COVID-19 pandemic - United States, January 2019-January 2022. MMWR Morb. Mortal. Wkly Rep. 2022 Feb 25; 71(8): 319–324. Epub 20220225. PubMed Abstract | Publisher Full Text

[3] 3. Malaty IC, Anderson S, Bennett S, et al.: Diagnosis and management of functional tic-like phenomena. J. Clin. Med. 2022; 11: 6470. PubMed Abstract | Publisher Full Text | Free Full Text

[4] 4. Pringsheim T, Ganos C, McGuire JF, et al.: Rapid onset functional tic-like behaviors in young females during the COVID-19 pandemic. Mov. Disord. 2021 Dec; 36(12): 2707–2713. Epub 20210831. PubMed Abstract | Publisher Full Text | Free Full Text

[5] 5. Conelea CA, Bervoets J, Davies EB, et al.: A call for caution: 'stop that' sentiments threaten tic research, healthcare and advocacy. Brain. 2022 May 24; 145(4): e18–e20. PubMed Abstract | Publisher Full Text

[6] 6. Robins E, Guze SB: Establishment of diagnostic validity in psychiatric illness: its application to schizophrenia. Am. J. Psychiatry. 1970; 126: 983–987. Publisher Full Text

[7] 7. Black KJ, Black ER, Greene DJ, et al.: Provisional Tic Disorder: What to tell parents when their child first starts ticcing [version 1]. F1000Res. 2016; 5: 696. PubMed Abstract | Publisher Full Text | Free Full Text

[8] 8. Openneer TJC, Huyser C, Martino D, et al.: Clinical precursors of tics: an EMTICS study. J. Child Psychol. Psychiatry. 2022 Mar; 63(3): 305–314. Epub 20210625. PubMed Abstract | Publisher Full Text | Free Full Text

[9] 9. Black KJ, Kim S, Schlaggar BL, et al.: The New Tics study: A novel approach to pathophysiology and cause of tic disorders. J. Psychiatr. Brain Sci. 2020; 5: e200012. Epub 2020/06/27. PubMed Abstract | Publisher Full Text | Free Full Text

[10] 10. Kim S, Greene DJ, Bihun EC, et al.: Provisional Tic Disorder is not so transient. Sci. Rep. 2019 Mar 8; 9(1): 3951. Epub 2019/03/10. PubMed Abstract | Publisher Full Text | Free Full Text

[11] 11. Baizabal-Carvallo JF, Jankovic J: The clinical features of psychogenic movement disorders resembling tics. J. Neurol. Neurosurg. Psychiatry. 2014 May; 85(5): 573–575. Epub 20131120. PubMed Abstract | Publisher Full Text

[12] 12. Buts S, Duncan M, Owen T, et al.: Paediatric tic-like presentations during the COVID-19 pandemic. Arch. Dis. Child. 2022 Mar; 107(3): e17. Epub 20211125. PubMed Abstract | Publisher Full Text

[13] 13. Dooley JM, Stokes A, Gordon KE: Pseudo-tics in Tourette syndrome. J. Child Neurol. 1994 Jan; 9(1): 50–51. PubMed Abstract | Publisher Full Text

[14] 14. Ganos C, Edwards MJ, Müller-Vahl K: "I swear it is Tourette's!": On functional coprolalia and other tic-like vocalizations. Psychiatry Res. 2016 Dec 30; 246: 821–826. Epub 20161017. PubMed Abstract | Publisher Full Text

[15] 15. Heintz CE, van Tricht MJ , van der Salm SM , et al.: Neuropsychological profile of psychogenic jerky movement disorders: importance of evaluating non-credible cognitive performance and psychopathology. J. Neurol. Neurosurg. Psychiatry. 2013 Aug; 84(8): 862–867. Epub 20130216. PubMed Abstract | Publisher Full Text

[16] 16. Larsh TR, Wu SW, Gilbert DL: Comparison of impairment in functional tic disorders versus Tourette syndrome. Pediatr. Neurol. 2022 Sep; 134: 83–84. Epub 20220628. PubMed Abstract | Publisher Full Text

[17] 17. Mink JW: Conversion disorder and mass psychogenic illness in child neurology. Ann. N. Y. Acad. Sci. 2013 Nov; 1304: 40–44. Epub 20131018. PubMed Abstract | Publisher Full Text

[18] 18. Monday K, Jankovic J: Psychogenic myoclonus. Neurology. 1993; 43(2): 349–352. Publisher Full Text

[19] 19. Robinson S, Hedderly T: Novel psychological formulation and treatment of "tic attacks" in Tourette syndrome. Front. Pediatr. 2016; 4: 46. Epub 20160511. PubMed Abstract | Publisher Full Text | Free Full Text

[20] 20. Hull M, Parnes M: Tics and TikTok: Functional Tics Spread Through Social Media. Mov. Disord Clin. Pract. 2021 Nov; 8(8): 1248–1252. Epub 20210701. PubMed Abstract | Publisher Full Text | Free Full Text

[21] 21. Pringsheim T, Martino D: Rapid onset of functional tic-like behaviours in young adults during the COVID-19 pandemic. Eur. J. Neurol. 2021 Nov; 28(11): 3805–3808. Epub 20210804. PubMed Abstract | Publisher Full Text | Free Full Text

[22] 22. Demartini B, Ricciardi L, Parees I, et al.: A positive diagnosis of functional (psychogenic) tics. Eur. J. Neurol. 2015 Mar; 22(3): 527–e36. Epub 20141209. PubMed Abstract | Publisher Full Text

[23] 23. Han VX, Kozlowska K, Kothur K, et al.: Rapid onset functional tic-like behaviours in children and adolescents during COVID-19: Clinical features, assessment and biopsychosocial treatment approach. J. Paediatr. Child Health. 2022 Jul; 58(7): 1181–1187. Epub 20220305. PubMed Abstract | Publisher Full Text | Free Full Text

[24] 24. Janik P, Milanowski Ł, Szejko N: Psychogenic tics: clinical characteristics and prevalence. Psychiatr. Pol. 2014 Jul-Aug; 48(4): 835–845. Tiki psychogenne: charakterystyka kliniczna i czestość wystepowania. PubMed Abstract

[25] 25. Olvera C, Stebbins GT, Goetz CG, et al.: TikTok tics: A pandemic within a pandemic. Mov. Disord. Clin. Pract. 2021; 8(8): 1200–1205. PubMed Abstract | Publisher Full Text | Free Full Text

[26] 26. Paulus T, Bäumer T, Verrel J, et al.: Pandemic tic-like behaviors following social media consumption. Mov. Disord. 2021 Dec; 36(12): 2932–2935. Epub 20210924. PubMed Abstract | Publisher Full Text

[27] 27. Black KJ, Arbuckle A:Supplemental Materials for Publication: Functional Tic-like Presentations Differ Strikingly from Provisional Tic Disorder. [Dataset]. OSF. Dec 2022. Publisher Full Text

[28] 28. Leckman JF, Riddle MA, Hardin MT, et al.: The Yale Global Tic Severity Scale: Initial testing of a clinical-rated scale of tic severity. J. Am. Acad. Child Adolesc. Psychiatry. 1989; 28(4): 566–573. PubMed Abstract | Publisher Full Text

[29] 29. Virtanen P, Gommers R, Oliphant TE, et al.: SciPy 1.0: Fundamental algorithms for scientific computing in Python. Nat. Methods. 2020 Mar; 17(3): 261–272. Epub 20200203. PubMed Abstract | Publisher Full Text | Free Full Text

[30] 30. Freeman RD, Zinner SH, Müller-Vahl KR, et al.: Coprophenomena in Tourette syndrome. Dev. Med. Child Neurol. 2009 Mar; 51(3): 218–227. Epub 20081204. PubMed Abstract | Publisher Full Text

[31] 31. Nilles C, Martino D, Berg L, et al.: Can the phenomenology of functional tic-like behaviours be sufficient to make the diagnosis? AACAP/CACAP annual meeting; 19 Oct 2022; Toronto, Ontario, Canada.2022.

[32] 32. Black KJ, Kim S, Yang NY, et al.: Course of tic disorders over the lifespan. Curr. Dev. Disord. Rep. 2021 Jun; 8(2): 121–132. Epub 2021/06/29. PubMed Abstract | Publisher Full Text | Free Full Text

Functional tic-like presentations differ strikingly from Provisional Tic Disorder

Abstract

Keywords

Introduction

Methods

Table 1. Comparison of various clinical features in FND-tic and in typical PTD.a

Data analysis

Ethical considerations

Results

Table 2. Diagnostic utility of the binary features in Table 1.a

Discussion

Data availability

Underlying data

Acknowledgements

References

Comments on this article Comments (0)

Open Peer Review

Comments on this article Comments (0)

Open Peer Review

Reviewer Status

Reviewer Reports

Comments on this article

Browse by related subjects

Competing Interests Policy

Stay Updated

Table 1. Comparison of various clinical features in FND-tic and in typical PTD.^a

Table 2. Diagnostic utility of the binary features in Table 1.^a