Neuropsychiatric phenotypes in functional movement disorder

Abstract

Objective Functional movement disorder (FMD), the motor-dominant subtype of functional neurological disorder, is a complex neuropsychiatric condition. Patients with FMD also manifest non-motor symptoms. Given that patients with FMD are diagnosed based on motor phenotype, the contribution of non-motor features to the neuropsychiatric syndrome is not well characterized. The objective of this hypothesis-generating study was to explore potential novel, neuropsychiatric FMD phenotypes by combining movement disorder presentations with non-motor comorbidities including somatic symptoms, psychiatric diagnoses, and psychological traits. Methods This retrospective chart review evaluated 158 consecutive patients with a diagnosis of FMD who underwent deep phenotyping across neurological and psychiatric domains. Demographic, clinical, and self-report features were analyzed. A data-driven approach using cluster analysis was performed to detect patterns when combining the movement disorder presentation with somatic symptoms, psychiatric diagnoses, and psychological factors. These new neuropsychiatric FMD phenotypes were then tested using logistic regression models. Results Distinct neuropsychiatric FMD phenotypes emerged when stratifying by episodic vs. constant motor symptoms. Episodic FMD was associated with hyperkinetic movements, hyperarousal, anxiety, and history of trauma. In contrast, constant FMD was associated with weakness, gait disorders, fixed dystonia, activity avoidance, and low self-agency. Pain, fatigue, somatic preoccupation, and health anxiety were common across all phenotypes. Conclusion This study found patterns spanning the neurological-psychiatric interface that indicate that FMD is part of a broader neuropsychiatric syndrome. Adopting a transdisciplinary view of illness reveals readily identifiable clinical factors that are relevant for the development and maintenance of FMD.

Factors Influencing Triage to Rehabilitation in Functional Movement Disorder

“…Constant FMD tends to present as gait disorders, weakness, and/or fixed dystonia, that can be targeted with motor retraining physiotherapy. 6 , 16 By contrast, episodic FMD presents as intermittent, hyperkinetic movements, and is associated with anxiety and hyperarousal. 16 This requires a fundamentally different therapeutic approach.…”

“… 6 , 16 By contrast, episodic FMD presents as intermittent, hyperkinetic movements, and is associated with anxiety and hyperarousal. 16 This requires a fundamentally different therapeutic approach. Borrowing techniques and concepts used in functional seizures can be helpful including trigger identification, recognizing and countering avoidance patterns, anxiety treatment and sympathetic nervous system regulation, and modified cognitive behavioral therapy.…”

“…Hyperarousal is often identified as part of a mental status exam, commonly associated with hyperkinetic FMD. 16 A dysregulated arousal/stress response is implicated in the pathophysiology of FMD, and is readily treatable using body relaxation techniques. 22 , 23 People‐pleasing traits reflect a behavioral pattern of deprioritizing one's own needs at the expense of others and a tendency for poor boundaries.…”

Altered brain network dynamics in motor functional neurological disorders: The role of the right temporo-parietal junction.

“…On the other hand, FND is characterized by diverse phenotypes and studies including a heterogeneous patient cohort might prevent clear results. Evidence for common features 22 and shared pathophysiology 5 across subtypes has recently been opposed by highlighted inter-patient diversity of clinical characteristics (e.g., symptom onset, gender distribution) 23 including neuropsychiatric features 24 or biological mechanisms underpinning different symptom manifestations 25 . A division based on symptom phenotype was proposed in Mueller, et al 26 , which applied different network centrality measures in resting-state fMRI and found distinct pathophysiological mechanisms for patients with pronounced functional weakness compared to patients with motor symptoms (tremor, myoclonus, dystonia, gait disorder), particularly a stronger network centrality of the left TPJ and precuneus.…”

Abnormalities of the Descending Inhibitory Nociceptive Pathway in Functional Motor Disorders

“…In a large population of FMD patients, pain was reported in a high percentage and often associated with some FMD phenotypes. 1 Pathophysiology of pain in FMD postulates biological factors and psychobehavioral mechanisms, but the precise mechanisms are still not completely clear. 2 The large brain network accessed during nociceptive processing is now commonly referred to as the "pain matrix", and it includes both the ascending lateral and medial pain systems and the descending inhibitory pain pathway.…”