A case series of functional movement disorders in paediatric population-phenomenology and clinical characteristics

Literature on functional movement disorders (FMD) in paediatric age group is scarce.

To study the phenomenology and characteristics of FMDs in paediatric age group.

The study included 13 children (8 girls and 5 boys) from a tertiary-care centre. Assessment of FMD was based on Fahn and Williams criteria. Data included phenomenology, socioeconomic background, electrophysiological, and imaging investigations.

Mean age of onset was 12.1 ± 2.3 years. Sudden onset and triggers like minor injuries and stressors were common precipitants. 68% of the children were from urban areas, 61% belonged to low socioeconomic status and 61.5% had intellectual disability. 72% had a precipitating factor. The most common phenomenology was myoclonus (38%), followed by tremor (30%), dystonia (23%), and abnormal gait (15%). Clues to suggest a functional etiology were, isolated or predominant involvement of the dominant upper limb, distractibility, and entrainment in the case of tremor. Significant variability in frequency, amplitude, and distribution of the FMD by distracting manoeuvres were helpful in establishing the diagnosis. Tremor and dystonia predominated in girls, while myoclonus manifested more often in boys. Ten subjects (76%) presented with an isolated movement disorder, while 3 patients (24%) had a combination of ≥ 2. Nine patients had other sensory symptoms most commonly headache.

FMDs were more common in children with intellectual disability than in those with normal IQ. Myoclonus was the most observed phenomenology. Among other comorbidities headache was the most common and depression followed by generalised anxiety were the most common psychiatric associations. Complete recovery is often possible with early intervention.