Psychogenic (Functional) Jaw-Opening Dystonia: Three Case Reports and a Comparison of Symptomatic Jaw-Opening Dystonia Associated with Organic Causes in the Literature

Background: Jaw-opening dystonia is very rarely reported, and involuntary jaw-opening dystonia as an initial manifestation of psychogenic (functional) movement disorder has not yet been reported. This study aimed to report unusual cases of psychogenic (functional) jaw-opening dystonia and to compare the clinical patterns between organic and psychogenic (functional) jaw-opening dystonia. Method: We enrolled three psychogenic (functional) movement disorder patients presenting involuntary severe jaw-opening dystonia as an initial manifestation. Moreover, we review previously reported cases and analyze the clinical pattern of organic psychogenic (functional) jaw-opening dystonia in comparison with our cases. Results: Among 10 cases, including our cases, the most common pattern of organic jaw-opening dystonic symptoms was the sustained pattern. By contrast, all three patients with psychogenic (functional) jaw-opening dystonia presented with a paroxysmal pattern. The major neuro-radiologically associated localizations of organic jaw-opening dystonia were the cerebellum and basal ganglia. Sensory feedback or “sensory tricks” were only observed in organic jaw-opening dystonia. Conclusion: The results of this clinically investigative study may provide support for the differential diagnosis of jaw-opening dystonia between organic and psychogenic (functional) etiologies. Additionally, if paroxysmal jawopening dystonia combined with inconsistent, incongruous hyperkinetic movement symptoms is present, diagnosis of a psychogenic (functional) movement disorder should be considered.