Moving Beyond Movement: Diagnosing Functional Movement Disorder

Abstract

Functional movement disorder (FMD) is a complex neuropsychiatric syndrome, encompassing abnormal movements and weakness, and is a common cause of potentially disabling neurological symptoms. It is vital to recognize that FMD is a syndrome, with nonmotor manifestations negatively affecting a patient's quality of life. This review highlights a diagnostic algorithm, where a history suggestive of FMD is combined with the presence of positive signs on examination and appropriate investigations to make the diagnosis. Positive signs indicate internal inconsistency such as variability and distractibility, and clinical findings that are incongruent with other known neurological disease. Importantly, the clinical assessment acts as the first opportunity to allow patients to understand FMD as the cause for their symptoms. Accurate and early diagnosis of FMD is necessary given that it is a treatable and potentially reversible cause of disability, with significant risk of iatrogenic harm associated with misdiagnosis.

Neuropsychiatric phenotypes in functional movement disorder

“…4,5 Taken together, these findings reinforce the concept of an FMD syndrome that is not sufficiently defined based on motor phenotype alone. 2,4,34 Our results confirm previous reports of a mean diagnostic delay of 6 years, and invalidating healthcare experiences experienced by patients. 21,35 We also identified a precipitating trigger for motor symptom onset in 83% of individuals, which is higher than other reports (48%-80%).…”

“…, 5 Taken together, these findings reinforce the concept of an FMD syndrome that is not sufficiently defined based on motor phenotype alone 2 4 , 34 …”

Factors Influencing Triage to Rehabilitation in Functional Movement Disorder

“…Functional motor symptoms were further classified as episodic or constant (Table 1). 16 FMD-relevant factors and rehabilitation-relevant factors are recurrent behavioral patterns observed in FMD drawn from the literature and subspecialist clinical experience. 10,17,18 These factors were identified based on interprofessional clinical impression at the time of the assessment, with findings explicitly documented during the history and examination.…”

“…9 In partnership with movement disorders clinics, specialist FMD clinics provide in-depth interprofessional patient assessments, education, triage, treatment planning, and rehabilitation, and tend to focus on aspects outside of traditional neurological or psychiatric consultation. 12 Such clinics are therefore uniquely poised to explore the various factors influencing treatment suitability and outcomes. 7 FMD is unique among neurological disorders in that it is diagnosed by neurologists, yet is often treated by other disciplines, including psychiatry and allied health.…”

Global Epidemiology of Movement Disorders: Rare or Underdiagnosed?

“…Patients who have FNDs have examination findings that demonstrate preserved neurologic function despite perceived deficits, for example, distractibility, variability, and entrainment of movements. 102 FNDs involve symptoms including tremor, paralysis, muscle cramping, dissociative symptoms, and seizure-like episodes (e.g., psychogenic nonepileptic spells or PNES). FNDs cause considerable distress and disability to those affected, and treatment is focused on rehabilitating motor function with physical and occupational therapy.…”