Emerging Trends in Functional Movement Disorders Consultations and the Impact of a Major Life Event

Abstract

Background

Awareness and major external events can contribute to the number of FMD cases.

Objective

To analyze trends in new Functional Movement Disorders (FMD) consultations and the impact of the COVID‐19 pandemic.

Methods

Retrospective analysis of FMD new consultations (2014–2024) at a tertiary movement disorders clinic. Trends and the COVID‐19 impact were analyzed with linear and segmented regression. Patient characteristics in the pre‐ and post‐pandemic periods were compared.

Results

Among 14,587 new consultations, 162 were FMD (79% female, mean age at onset 44.7 ± 18.3 years). FMD consultations increased slowly over time, with a marked surge after 2021. The significant rise was observed during the three years post‐pandemic, followed by a return to the pre‐pandemic slope. Pre and post‐pandemic groups’ characteristics were almost similar.

Conclusions

FMD consultations increased over time and significantly after the COVID‐19 pandemic. This underscores the influence of increased awareness and external factors.

Functional movement disorders (FMD) are a subtype of functional neurological disorders (FND) that encompass both hyperkinetic (eg, tremor) and hypokinetic disorders (eg, parkinsonism). They represent around 3–10% of patients referred to movement disorders services. ¹ , ² Growing interest in FMD has emerged in recent years, driven by the advances in the understanding of their mechanisms, their notable prevalence, improvements in diagnostic accuracy, and the development of therapeutic approaches. ³ , ⁴ This heightened awareness is likely associated with an increased number of diagnoses in movement disorders clinics. ⁵ Additionally, other external events have been observed to cause a transitory increase in certain FMD, ⁶ particularly in the case of the COVID‐19 pandemic and functional tics. ⁷ , ⁸ Consequently, we conducted a retrospective chart review of patients diagnosed with FMD in the past 10 years at a movement disorders clinic to ¹ : assess trends over time, ² evaluate the influence of the COVID‐19 pandemic, and ³ compare patients’ clinical and demographic characteristics before and after the pandemic.

Methods

We conducted a retrospective analysis of new cases of FMD among adult patients from a single center (a tertiary movement disorders clinic in Buenos Aires, Argentina), between January 2014 and December 2024. Patients were seen directly from the center where the clinic is located, as well as from other neurological facilities in Argentina through referrals, or they sought an expert opinion independently.

Patients were included if they were diagnosed with an FMD by the movement disorders specialist based on the features of inconsistency and incongruence, which aligns with the criteria of Gupta & Lang. ⁹ FMD diagnosis was supported by complementary recommendations ¹⁰ and the Espay & Lang phenotypic criteria. ¹¹ Additionally, a clear ruling out of any known neurological disorder responsible for the observed pattern was required. Patients with an uncertain diagnosis were excluded.

We extracted demographic and clinical variables related to the phenomenology of FMD and comorbidities. History of FMD, other FNDs, precipitating factors, and accompanying symptoms were gathered from the free‐text sections of the medical records. Data were validated through qualitative thematic analysis by researchers to ensure reliability, as no specific scales were used.

To evaluate the trend in the incidence of new FMD consultations, we plotted the six‐month number of newly diagnosed FMD patients based on the date of the first appointment and adjusted for the total number of new patients evaluated at the clinic. To explore the tendency of the slope over time, we used simple linear regression with time as the independent variable and the number of newly diagnosed FMD patients as the dependent variable.

To assess the changes in the incidence of FMD consultations in the post‐pandemic period, we used an interrupted time series (ITS) analysis through segmented linear regression. This model evaluates changes in the slopes before and after one event (the pandemic), and level change (intersection of the two slopes). The intersection was set in the first six months of 2021 (post‐quarantine), since after that, there was more regular access to health services. Finally, we compared patients’ demographic and clinical variables before (2018–2019) and after the pandemic (2021–2022).

Continuous variables were summarized by mean, median, standard deviation, and interquartile range, based on distribution. Categorical variables were expressed as absolute frequencies and proportions. Means were compared with Student's t‐test or the Mann–Whitney U test. Proportions were compared with Chi‐square or Fisher's exact test. Analyses were performed using R software. A P‐value <0.05 was considered significant.

Results

Among 14,587 new consultations in the period evaluated, 162 (1.11%) were FMD, with 129 (79.6%) being female and a mean age at onset of 44.7 ± 18.3 years. The most common FMDs were mixed 42 (25.1%), tremor 24 (14.4%), and dystonia 16 (9.6%) (Table 1).

TABLE 1.

Demographic and clinical characteristics

Variable	All patients (2014–2024) n = 162	Pre‐pandemic (2018–2019) n = 22	Post‐pandemic (2021–2022) n = 51	P‐value
Sex, n (%)
Female	129 (79.6)	21 (95.5)	37 (72.5)	0.03
Male	33 (20.4)	1 (0.5)	14 (27.5)
Age at onset, years, mean ± SD	44.7 ± 18.4	44.5 ± 23.5	41.8 ± 17.4	0.64
Time from onset to diagnosis, months, median (IQR)	24 (9–48)	18 (5.5–66)	24 (11.5–36)	0.81
FMD phenotype, n (%)
Mixed	41 (25.3)	4 (18.2)	13 (25.5)	0.49
Tremor	24 (14.8)	3 (13.6)	7 (13.7)	1
Dystonia	15 (9.3)	3 (13.6)	6 (11.8)	1
Parkinsonism	22 (6.8)	0 (0)	4 (7.8)	0.31
Gait abnormality	10 (6.2)	1 (4.5)	1 (2)	0.54
Myoclonus	9 (5.6)	5 (22.7)	2 (3.9)	0.02
Oromandibular movements	7 (4.3)	0 (0)	2 (3.9)	1
Tics	7 (4.3)	1 (4.5)	1 (2)	0.52
Undifferentiated	27 (16.7)	5 (22.7)	10 (19.6)	0.76
Other	6 (3.7)	0 (0)	2 (3.9)	0.55
Other FND, n (%)
FDS	28 (17.3)	4 (18.2)	10 (19.6)	1
Cognitive	14 (8.6)	3 (13.6)	5 (9.8)
Sensory	5 (3.1)	1 (4.6)	2 (3.9)
PPPD	5 (3.1)	2 (9.1)	0 (0)
Visual	3 (1.9)	1 (4.6)	1 (2)
Neurological comorbidity, n (%)	76 (46.9)	9 (40.9)	19 (37.3)	0.76
Psychiatric comorbidity, n (%)	93 (65.5)	11 (73.3)	32 (72.7)	1
Non‐motor symptoms, n (%)
Fatigue	46 (28.8)	5 (23.8)	10 (19.6)	0.69
Sensory	43 (26.9)	6 (28.6)	14 (27.5)	0.92
Pain	83 (51.9)	9 (42.9)	24 (47.1)	0.75
Headache	47 (29.4)	5 (23.8)	13 (25.5)	0.88
Cognitive	57 (36.6)	8 (38.1)	16 (31.4)	0.58
Persistent dizziness	24 (15)	6 (28.6)	5 (9.8)	0.07
Sleep problems	78 (48.8)	10 (47.6)	21 (41.2)	0.62
Anxiety	102 (63.7)	14 (66.7)	34 (66.7)	1
Low mood	93 (58.1)	11 (52.4)	30 (58.8)	0.62

Abbreviations: FND, Functional neurological disorder; FMD, Functional movement disorder; FDS, Functional/dissociative seizures; PPPD, Persistent Postural‐Perceptual Dizziness.

The referral source of patients was: within our center in 45 patients (27.7%), outside our center in 70 (43.2%), self‐referred in 11 (6.8%), and unknown in 20 (12.3%). Additionally, 16 patients (9.9%) were already being followed in the movement disorders clinic prior to the diagnosis of FMD (Table S1). The referrals within our center were for confirmation of diagnosis, mainly from general neurology (37.8%), other neurological specialties (22.2%), and the epilepsy clinic (17.8%). Of the outside referrals, seven (10%) were from psychiatrists, four (5.7%) from neurologists, three (4.3%) from other physicians, and not specified in the remaining 56 patients (80%).

The number of new consultations of FMD patients increased progressively over time (Fig. 1A). In 2014, there were two FMD patients (0.13 per 100 new patients with other movement disorders), while in 2024, there were 24 patients (1.81 per 100 new patients with other movement disorders). A consistent upward trend in newly diagnosed FMD cases was observed since 2014, with a notable acceleration in 2021. A simple linear regression analysis demonstrated a significant increase in new FMD diagnoses over the study period (Fig. 1B). In the segmented linear regression, there was weak pre‐pandemic upward trend in FMD new patients (slope 0.05), a sudden rise in the level of the intersection point (level change: 1.1; P < 0.05, 95% CI: 1.49–7.68), and an apparent tendency to return to pre‐pandemic rates (slope − 0.09) (Fig. 1C).

Figure 1.

(A) Line chart of FMD patients displaying new FMD consultations per 100 new patients. Historical milestones in diagnostic criteria, task forces, dedicated study groups, and the foundation of FNDS are summarized over time. The size of the circles is proportional to the number of milestones each year. The shaded area is for the COVID‐19 pandemic. (B) Linear regression. (C) Segmented linear regression. The first slope represents the trend before the pandemic, and the second slope represents the post‐pandemic trend. Espay & Lang, criteria for FMD phenotypes; FMD, Functional Movement Disorders; FNDS, Functional Neurological Disorders Society; HD, Huntington's Disease; IAPRD, International Association of Parkinsonism and Related Disorders; MDS, Movement Disorders Society; MSA, Multiple System Atrophy; PD, Parkinson's disease; PSP, Progressive supranuclear palsy; S‐FMDRS, MDS Simplified Functional Movement Disorder Rating Scale.

There were 22 (13.6%) and 51 (31.5%) patients in the pre‐pandemic and post‐pandemic groups, respectively. Most of the clinical and demographic characteristics were similar between both groups (Table 1 and S2); however, there was a significantly greater proportion of male patients in the latter group (0.5% vs 27.5%, P = 0.03), and functional myoclonus in the former (22.7% vs 3.9%, P = 0.02). Of the post‐pandemic group, 12 (23.5%) patients reported the onset of their symptoms in the pandemics, and eight (15.7%) reported a precipitant factor related to the pandemic: quarantine in four cases (50%), mild COVID‐19 infection in two (25%), or the COVID‐19 vaccination in two (25%).

Discussion

The main finding of this single‐center study is the progressive increase over the past decade in the number of newly diagnosed FMD adult cases. We also found a significant increase after the COVID‐19 pandemic, which persisted in the first post‐pandemic years. Additionally, we found no significant differences in the clinical and demographic characteristics of FMD patients between the immediate pre‐ and post‐pandemic years.

Before further discussion, we should disclose that the present work is limited by its retrospective nature, which restricts our ability to establish causality and may introduce biases arising from the data collection process, as some crucial information needed for further conclusions is missing. Inherent referral bias in tertiary care facilities must also be considered, especially since half of the patients were referred from outside our center, and medical information for referral was not available in 80% of them, as referral letters are not usually used, or the information was not added to the clinical record. This may limit our capacity to rule out shifts in referral patterns as a driver of the observed trend. Moreover, the single‐center design of this study is an important limitation to its generalizability, particularly given the highly variable healthcare infrastructure across Argentina and the differences in access to specialists.

Noteworthy, the frequency of FMD in our cohort remains low but approaches the 3–10% incidence reported in other cohorts. ¹ , ² Although a lower incidence of FMD in the general Argentinian population due to demographic differences cannot be ruled out, several other factors may explain this discrepancy, such as low referral rates from neurologists and a diminished awareness of FMD among movement disorder specialists. It is important to note that the low frequency of FMD in this cohort represents a low starting point, and that subsequent slope changes may appear steeper and statistically significant despite reflecting only small increases in the number of FMD consultations. Therefore, some caution is needed when interpreting the trend. Additionally, we cannot exclude the possibility that changes in diagnostic awareness or case capture may better explain the findings.

Our findings suggest a general increasing trend in consultations for FMD, although we cannot realistically disentangle the reasons for this upward tendency, as the statistical analysis only considered the total number of consultations and did not adjust for other significant variables that may have influenced them (eg, behavior of patients seeking care or referrals from clinicians). Moreover, we cannot isolate the influence of social media, particularly during the pandemic and post‐pandemic periods, when there was a surge in consultations for FMD, especially in functional tics. ⁵ , ⁷ For the aforementioned reasons, we cannot reliably interpret the trend in FMD consultations as being caused by a single factor, nor can we quantify the individual contribution of each factor. Further prospective studies are needed to explore whether these trends represent an increase in the incidence of FMD or an enhancement in awareness within the general neurology setting or population. We also encourage future studies to adopt a multicentric approach to increase the number of cases.

Several milestones in the past decade may explain the increasing number of FMD diagnoses. These include the development of more robust diagnostic criteria, ⁹ , ¹¹ the refinement of criteria for other movement disorders, the creation of dedicated groups for the study of FMD, and the emergence of organizations such as the Functional Neurological Disorders Society (FNDS) (Fig. 1A). Taken together, these factors may explain the growing awareness of FMD among general neurologists and movement disorder specialists.

FMD have historically shown episodic increases in association with major life events such as war, or the so‐called mass psychogenic illness. ⁶ This phenomenon has already been described during pandemics and in response to the COVID‐19 vaccination. ¹² Previous studies have also found an association between major life events and the development of other neurological diseases, such as Parkinson's disease. ¹³ Our study broadens the understanding of the impact of these events by demonstrating a sustained increase in new FMD cases over the three years following the pandemic. Although we cannot entirely exclude the effects of diagnostic awareness, patient‐seeking behavior, or the influence of social media, the rise and sustained number of FMD consultations post‐pandemic might, to some extent, reflect the cumulative psychosocial burden experienced during the pandemic period. ¹⁴ Nevertheless, it is important to note that psychological stressors are not a mandatory criterion for the diagnosis of FMD, and in many cases, no such stressors are identified.

We did not find significant differences in most clinical and demographic characteristics when comparing the immediate pre‐pandemic (2018–2019) and post‐pandemic (2021–2022) groups, except for a greater representation of male patients in the latter, which aligns with the demographic characteristics of FMD previously reported. ¹⁵ Furthermore, unlike in the pediatric population, ¹⁶ we did not observe differences in the incidence of functional tics in adults. However, there were a small number of patients in the pre‐pandemic period (n = 22) compared to the post‐pandemic period (n = 51); hence, our power to detect subtle clinical or demographic differences may have been limited due to the sample size imbalance. It is possible that a more in‐depth characterization of patients’ clinical and neuropsychiatric profiles may better identify differences between the groups.

In conclusion, albeit with a lower incidence than reported in the literature, in this first Argentine series of FMD, the number of FMD cases consulting a movement disorders clinic has increased over time, with a significant and sustained rise observed since the COVID‐19 pandemic. Although this tendency may have been influenced by several factors, such as patient‐seeking behavior and referral patterns, it underscores an emerging trend and the impact of a major external factor on the proportion of FMD consultations.

Author Roles

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

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

G.L.: 1A, 1B, 2C, 3C

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

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

Disclosures

Ethical Compliance Statement: The study protocol complied with the Helsinki Declaration principles and was approved by the local Institutional Review Board. Informed consent was not required for this work. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines.

Funding Sources and Conflict of Interest: No specific funding was received for this work. The authors declare that there are no conflicts of interest relevant to this work.

Financial Disclosures for the Previous 12 Months: DSM‐M is supported by the Edmond J. Safra Foundation Fellowship in Movement Disorders (Class of 2027).

Supporting information

Supplemental Table S1. Prior diagnosis in the patients followed at the movement disorders clinic before the FMD diagnosis (n = 16)

Supplemental Table S2. Characteristics of the FMD and detailed comorbidities

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.