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The complex syndrome of functional neurological disorder

Published online by Cambridge University Press:  07 January 2022

Zuzana Forejtová ,
Tereza Serranová Open the ORCID record for Tereza Serranová [Opens in a new window] ,
Tomáš Sieger Open the ORCID record for Tomáš Sieger [Opens in a new window] ,
Matěj Slovák ,
Lucia Nováková ,
Gabriela Věchetová ,
Evžen Růžička Open the ORCID record for Evžen Růžička [Opens in a new window]  and
Mark J. Edwards Open the ORCID record for Mark J. Edwards [Opens in a new window]
Zuzana Forejtová
Affiliation:
Department of Neurology and Centre of Clinical Neuroscience, General University Hospital and First Faculty of Medicine, Charles University, Prague, 128 21, Czech Republic
Tereza Serranová*
Affiliation:
Department of Neurology and Centre of Clinical Neuroscience, General University Hospital and First Faculty of Medicine, Charles University, Prague, 128 21, Czech Republic
Tomáš Sieger
Affiliation:
Department of Neurology and Centre of Clinical Neuroscience, General University Hospital and First Faculty of Medicine, Charles University, Prague, 128 21, Czech Republic Department of Cybernetics, Faculty of Electrical Engineering, Czech Technical University, Prague, 166 27, Czech Republic
Matěj Slovák
Affiliation:
Department of Neurology and Centre of Clinical Neuroscience, General University Hospital and First Faculty of Medicine, Charles University, Prague, 128 21, Czech Republic
Lucia Nováková
Affiliation:
Department of Neurology and Centre of Clinical Neuroscience, General University Hospital and First Faculty of Medicine, Charles University, Prague, 128 21, Czech Republic
Gabriela Věchetová
Affiliation:
Department of Neurology and Centre of Clinical Neuroscience, General University Hospital and First Faculty of Medicine, Charles University, Prague, 128 21, Czech Republic
Evžen Růžička
Affiliation:
Department of Neurology and Centre of Clinical Neuroscience, General University Hospital and First Faculty of Medicine, Charles University, Prague, 128 21, Czech Republic
Mark J. Edwards
Affiliation:
Neuroscience Research Centre, Institute of Molecular and Clinical Sciences, St George's University of London, London, SW17 0RE, UK
*
Author for correspondence: Tereza Serranova, E-mail: Tereza.Serranova@vfn.cz
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Abstract

Background

Patients with functional neurological disorders (FND) often present with multiple motor, sensory, psychological and cognitive symptoms. In order to explore the relationship between these common symptoms, we performed a detailed clinical assessment of motor, non-motor symptoms, health-related quality of life (HRQoL) and disability in a large cohort of patients with motor FND. To understand the clinical heterogeneity, cluster analysis was used to search for subgroups within the cohort.

Methods

One hundred fifty-two patients with a clinically established diagnosis of motor FND were assessed for motor symptom severity using the Simplified Functional Movement Disorder Rating Scale (S-FMDRS), the number of different motor phenotypes (i.e. tremor, dystonia, gait disorder, myoclonus, and weakness), gait severity and postural instability. All patients then evaluated each motor symptom type severity on a Likert scale and completed questionnaires for depression, anxiety, pain, fatigue, cognitive complaints and HRQoL.

Results

Significant correlations were found among the self-reported and all objective motor symptoms severity measures. All self-reported measures including HRQoL correlated strongly with each other. S-FMDRS weakly correlated with HRQoL. Hierarchical cluster analysis supplemented with gap statistics revealed a homogenous patient sample which could not be separated into subgroups.

Conclusions

We interpret the lack of evidence of clusters along with a high degree of correlation between all self-reported and objective measures of motor or non-motor symptoms and HRQoL within current neurobiological models as evidence to support a unified pathophysiology of ‘functional’ symptoms. Our results support the unification of functional and somatic syndromes in classification schemes and for future mechanistic and therapeutic research.

Keywords

Cluster analysisconversion disordercorrelationfunctional movement disordersfunctional neurological disordergap statisticsmedically unexplained symptomsmotor phenotypes
Type
Original Article
Information
Psychological Medicine , Volume 53 , Issue 7 , May 2023 , pp. 3157 - 3167
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Copyright
Copyright © The Author(s), 2022. Published by Cambridge University Press

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Footnotes

*

These authors contributed equally to this work.

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