Characteristics of two distinct clinical phenotypes of functional (psychogenic) dystonia: follow-up study
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The fixed dystonia phenotype was originally established as a prototype of functional dystonia. Nevertheless, in recent reports different functional dystonia phenotypes have been recognized with dystonic movement comprising phasic instead of tonic contraction.
To examine clinical characteristic in all patients with dystonia who fulfilled the criteria for functional movement disorders irrespective of phenotype in an attempt to determine parameters of clinical presentations that might impact the disease progression pattern and outcome.
Patients presented with dystonia features incompatible with organic disease without other features required for the diagnosis of functional movement disorders were analyzed and prospectively followed-up. The two-step cluster analysis was performed to obtain the subgroups of dystonia phenotypes.
The two-step cluster analysis extracted two subgroup of patients. Patients of the first cluster (68.8%) presented with “mobile” dystonia (84.9%), of cranial/neck/trunk localization (90.9%), fluctuated clinical course (69.7%), with frequent additional movement or other functional neurological disorders (63.6%) during follow-up. In the second cluster (31.2%) all of the patients presented with “fixed” dystonia of extremities, and the clinical course was characterized by either the disease progression (60%), or continuous without improvement (26.7%), and rare occurrence of additional functional neurological disorders (13.3%).
In terms of clinical and demographic features as well as pattern of disease progression there are two clinical phenotypes in patients with functional dystonia. Distinctive features of incongruence and inconstancy are characteristic for “mobile” functional dystonia subgroup of patients.
KeywordsFunctional Dystonia Mobile Follow-up
Compliance with ethical standards
This study was supported by the Ministry of Education and Science of the Republic of Serbia (Grant no. 175090).
Conflicts of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
All persons gave their informed consent prior to their inclusion in the study. The manuscript does not contain clinical studies or patient data.
Supplementary material 1 (MP4 2286 kb) Video 1. Illustrative case with “mobile” subtype of functional dystonia. Segment 1: Action induced intermittent muscle contraction of the right arm causing abnormal repetitive movements and postures; Segment 2: Additional functional movement disorders: ipsilateral facial and neck jerks
Supplementary material 2 (MP4 5266 kb) Video 2. Illustrative case with “mobile” subtype of functional dystonia. Segment 1: Minimal dystonia of left feet in the rest and during the shoe, with worsening during walk. Segment 2: Disease progression with right hand functional tremor
Supplementary material 3 (MP4 3825 kb) Video 3. Illustrative case with “fixed” subtype of functional dystonia with characteristic disease progression: “fixed” dystonia of the right foot at presentation with dystonia spreading to the left foot and right hand
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