Objective: To characterize various presentations of pseudo-dystonia and features that distinguish it from dystonia based on review of 12 video cases and the published literature.

Background: Dystonia is characterized by abnormal muscle contractions, sustained or intermittent, that result in involuntary movements and postures (Albanese et al. Mov Disord 2013). It can be inherited, acquired, or idiopathic (Albanese et al. Mov Disord 2013). Pseudo-dystonia, also called fixed dystonia, may appear similarly to dystonia, but has distinct features and is typically due to other identifiable causes (Schrag et al. Brain 2004). These include complex regional pain syndrome and peripheral nerve injury, muscle weakness, stiff limb syndrome, orthopedic pathology, compensatory mechanisms (such as head tilt with a cranial nerve IV palsy or head rotation with a retropharyngeal abscess), and other movement disorders. It can be difficult to distinguish between dystonia and pseudo-dystonia clinically; attention to particular features is essential to differentiating these.

Methods: We reviewed 12 video cases of patients who presented with pseudo-dystonia, obtaining clinical information from the medical records. Each was characterized by age of onset, gender, symptom progression, affected body region, fixed versus dynamic nature, associated symptoms, triggering events, and diagnosis.

Results: The age of onset varied widely among our subjects, ranging from birth to 65 years old with a mean of 30. Both genders were affected, 5 females and 7 males. Onset was acute in 3/12, sub-acute or gradual in 7/12, and present at birth in 2/12 patients. Body regions involved were the neck, foot, leg, hand, and finger. Presentation was focal in 10/12 cases and segmental in 2/12. In 8/12 patients posturing was fixed, while in 4/12 it was episodic at onset. The most common associated symptom was pain (6/12), the next weakness (3/12). Triggering events were present in 3/12 cases. The underlying etiology varied, including complex regional pain syndrome, complex motor tics, stiff limb syndrome, ligament laxity, myotonic dystrophy, muscle fibrosis, arthritis, and myopathy.

Conclusions: Our series highlights the wide range of etiology responsible for pseudo-dystonia. Regardless of the cause, distinct features distinguish this presentation from true dystonia. Recognizing this can help guide appropriate work-up and treatment for these patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/distinguishing-pseudo-dystonia-from-dystonia-a-case-series/