Objective: We evaluated patients with FMD and identified those with troublesome or even disabling symptoms or complications due to the treatment of the condition.

Background: Functional neurologic disorders, including functional movement disorders (FMD) are historically thought to be “benign” and self-limited conditions.

Method: A retrospective cohort study included patients evaluated at a pediatric movement disorders clinic with a diagnosis of functional neurologic symptom disorder (based on ICD10 codes and/or documentation in the clinical note) from 2015-2021 . Demographics, phenomenology, medical history, brain imaging, electroencephalograms, and medical reports were reviewed. Malignant functional movement disorders were defined as a condition resulting in at least one of the following: (1) invasive procedure(s); (2) morbidity/mortality; (3) more than one admission to the hospital for management of functional symptoms or management of complications related to the management of functional symptoms.

Results: total of 211 charts were queried with 89 patients meeting inclusion criteria for FMD (77.5% female). Of these patients, 18 met the criteria for malignant FMD (20.2%). The dominant phenomenologies of FMD included myoclonus (24.7%), tremor (38.2%), dystonia (19.1%), tics (30%), stereotypy (15.7%), gait abnormality (9%), and others (29%). In patients with malignant FMD, the most common phenomenology was dystonia (41.2%), but many patients had a combination of different hyperkinetic movement disorders. Psychiatric comorbidities were common in patients with FMD (65%) and were slightly more common in patients with malignant FMD (72.2%). Suicidal ideation and/or attempts were common within this cohort (24.7% N=22 in all and 27.7% N=5 in malignant FMD). Patients with chronic use of assistive devices such as wheelchairs were more likely to have malignant FMD (8.5% vs 27.7%). Morbidity associated with malignant FMD included subdural hematoma, subconjunctival hemorrhage, concussions, traumatic rhabdomyolysis, spinal fracture, and laryngomalacia. One patient underwent below the knee amputation while another received intrathecal baclofen pump.

Conclusion: Although most patients with FMD have a benign course, a small percentage of patients experience severe, long-term complications due to this condition, termed malignant FMD, and warrant close monitoring and prompt treatment to prevent morbidity.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/malignant-functional-movement-disorders-in-children-experience-from-a-tertiary-care-center/