Objective: The coexistence of Parkinson’s disease (PD) and functional movement disorders (FMD) is increasingly recognized but remains underdiagnosed. Functional dyskinesia, a subtype of FMD, can mimic or overlap with levodopa-induced dyskinesia (LID) in PD patients, leading to diagnostic confusion and inappropriate treatment adjustments. Differentiating these conditions is crucial, as management strategies differ fundamentally: LID responds to dopaminergic modulation, whereas functional dyskinesia requires physiotherapy, psychotherapy, and patient education.

Background: To describe a case of functional dyskinesia in a patient with established PD, highlighting the diagnostic approach, therapeutic implications, and the importance of multidisciplinary management.

Method: A 68-year-old woman with a 10-year history of PD presented with increasingly complex, variable involuntary movements that were unresponsive to levodopa adjustments. Clinical evaluation included detailed history, neurological examination with video recording, and assessment using the Unified Parkinson’s Disease Rating Scale (UPDRS). Neuropsychological assessment and laboratory tests were performed to exclude other causes. The diagnosis of functional dyskinesia was based on validated criteria (Gupta & Lang, 2009), including inconsistency, incongruence with typical LID, distractibility, and response to placebo.

Results: The patient exhibited choreiform and dystonic movements that varied in distribution and timing, often exacerbated by attention and alleviated by distraction. Unlike LID, these movements did not correlate with levodopa dosing and were associated with non-motor symptoms such as anxiety and fatigue. After diagnosis, dopaminergic therapy was maintained unchanged, and a tailored rehabilitation program (physical therapy with motor reprogramming, cognitive-behavioral therapy) was initiated. Within 3 months, the patient reported a 50% reduction in dyskinesia severity and improved quality of life.

Conclusion: Functional dyskinesia can coexist with PD and should be suspected when involuntary movements deviate from typical LID patterns. Accurate diagnosis prevents unnecessary medication changes and enables effective non-pharmacological interventions. A multidisciplinary approach integrating neurology, psychiatry, and rehabilitation is essential for optimal outcomes.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/functional-dyskinesia-in-a-patient-with-parkinsons-disease-a-diagnostic-and-therapeutic-challenge/