Recognizing Uncommon Presentations of Psychogenic (Functional) Movement Disorders
Background: Psychogenic or functional movement disorders (PMDs) pose a challenge in clinical diagnosis. There are several clues, including sudden onset, incongruous symptoms, distractibility, suggestibility, entrainment of symptoms, and lack of response to otherwise effective pharmacological therapies, that help identify the most common psychogenic movements such as tremor, dystonia, and myoclonus.
Methods: In this manuscript, we review the frequency, distinct clinical features, functional imaging, and neurophysiological tests that can help in the diagnosis of uncommon presentations of PMDs, such as psychogenic parkinsonism, tics, and chorea; facial, palatal, and ocular movements are also reviewed. In addition, we discuss PMDs at the extremes of age and mass psychogenic illness.
Results: Psychogenic parkinsonism (PP) is observed in less than 10% of the case series about PMDs, with a female–male ratio of roughly 1:1. Lack of amplitude decrement in repetitive movements and of cogwheel rigidity help to differentiate PP from true parkinsonism. Dopamine transporter imaging with photon emission tomography can also help in the diagnostic process. Psychogenic movements resembling tics are reported in about 5% of PMD patients. Lack of transient suppressibility of abnormal movements helps to differentiate them from organic tics. Psychogenic facial movements can present with hemifacial spasm, blepharospasm, and other movements. Some patients with essential palatal tremor have been shown to be psychogenic. Convergence ocular spasm has demonstrated a high specificity for psychogenic movements. PMDs can also present in the context of mass psychogenic illness or at the extremes of age.
Discussion: Clinical features and ancillary studies are helpful in the diagnosis of patients with uncommon presentations of psychogenic movement disorders.