Idiopathic adult‐onset dystonia has motor and non‐motor symptoms. Research of non‐motor symptoms, particularly cognitive impairment, is difficult to interpret given contradictory outcomes, stemming from heterogeneous populations, small samples and comorbidities, including poor sleep and depression. Studies of social cognition focus on cervical dystonia (CD) and use testing measures often requiring time or tools impractical in the outpatient setting. 1 , 2 , 3 , 4 , 5 We aimed to perform a pilot investigating social cognition using a clinically applicable tool in CD and blepharospasm (BSP).
We performed a cross‐sectional study evaluating social cognition in CD (n = 29), BSP (n = 26) and healthy controls (HC, n = 18). Participants with deficits in global cognition, depression, or anxiety, dystonic spread or combined forms, were excluded. We assessed the social behavior subcategory of social cognition using the Social Norms Questionnaire (SNQ‐22), an easily performed test that assesses appropriateness in hypothetical social scenarios. The total score is the summation of correct responses, and errors result from breaking norms or over adhering to perceived norms.
We found no differences between groups in sex, age, education, income, global cognition, or anxiety (Table 1 ). HADS‐D was different across groups (F = 9.73, P = .0003), driven by higher depression scores in CD (P = .0003) and BSP (P = .012) than controls.
TABLE 1.
Demographics and clinical features of study participants
| Variable | CD (n = 29) | BSP (n = 26) | HC (n = 18) | P‐value* |
|---|---|---|---|---|
| Age | 62.51 (9.12) | 66.23 (7.67) | 65.67 (8.56) | 0.25 |
| Female | 20 (69%) | 22 (85%) | 11 (61%) | 0.19 |
| College Graduate | 23 (79%) | 18 (69%) | 14 (78%) | 0.67 |
| MoCA | 27.69 (1.11) | 27.58 (1.47) | 28.17 (1.15) | 0.31 |
| HADS‐A | 5.48 (2.73) | 4.58 (2.73) | 4.00 (2.57) | 0.17 |
| HADS‐D | 4.24 (2.60) | 3.38 (2.25) | 1.56 (1.76) | 0.0003 |
| TWSTRS | 27.76 (11.31) | – | – | – |
| BSP Rating Scale | – | 5.85 (4.06) | – | – |
| Tremor Present | 19 (66%) | – | – | – |
Demographics and clinical characteristics across the study groups were compared using chi‐squared and F‐tests as appropriate. Values (percentages) shown for categorical variables, means (SD) for continuous variables.
Abbreviations: CD, cervical dystonia; BSP, blepharospasm; HC, healthy controls; SD, standard deviation; MoCA, Montreal Cognitive Assessment; HADS‐A, Hospital Anxiety and Depression Scale‐Anxiety; HADS‐D, Hospital Anxiety and Depression Scale‐Depression; TWSTRS, Toronto Western Spasmodic Torticollis Rating Scale.
SNQ‐22 scores were different across groups (20.17 ± 1.30 (CD), 20.92 ± .89 (BSP), 21.06 ± .94 (HC), F = 4.64, P = .015). Using an ANCOVA‐type model, adjusting for HADS‐D resulted in no significant changes (F = 6.15, P = .0042). Pairwise comparisons revealed differences between CD and BSP (t = 2.63, P = .03) and between CD and HC (t = 2.80, P = .02), but not between BSP and HC (t = .47, P = .89).
In a post‐hoc analysis comparing CD participants with (n = 19) and without head tremor (n = 10), SNQ‐22 scores did not differ (t = 1.75, P = .09).
This is the first report to identify impairment in any aspect of social cognition in patients with CD not present in those with BSP. Correlational analyses between social cognition, demographics, mood, global cognition, and sleep did not identify alternative explanations for our findings. Our study supports differences in social cognition across distinct phenotypes of dystonia. A Canadian study, however, found less impairment on the SNQ‐22 in their CD cohort. 5 This discrepancy may be due to cultural differences or other study differences and highlights the need for more expansive studies.
Limitations in our study include our limited cognitive assessment, small sample size, and the resultant inability to control for varying treatments. Future studies could benefit from inclusion of additional focal dystonia phenotypes, utilization of imaging to strengthen relationships between clinical and pathophysiological abnormalities, and broader cognitive assessments, which may identify larger absolute differences in other areas of social cognition.
Our pilot study is the first to identify a deficit in social cognition in CD, not present in BSP. This finding suggests distinct neural network dysfunction between these two forms of focal dystonia and raises the possibility that those with CD may benefit from deep brain or transcranial stimulation targeting unique from BSP. To best serve our patients with dystonia, we must understand the breadth and variability of non‐motor phenotypes amongst the various types of focal dystonia to best address their clinical needs and improve quality of life.
Author Roles
(1) Research project: A. Conception, B. Organization, C. Execution; (2) Statistical Analysis: A. Design, B. Execution, C. Review and Critique; (3) Manuscript: A. Writing of the first draft, B. Review and Critique.
J.F.: 1A, 1B, 1C, 2A, 2B, 2C, 3A, 3B
B.H.: 1B
S.H.: 1A, 2C, 3B
S.S.: 2A, 2B, 2C, 3B
B.B.: 1A, 1B, 2A, 2C, 3B
Disclosures
Ethical Compliance Statement: The study was approved by the Colorado Multiple Institutional Review Board and all participants provided informed consent before taking part in the study. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work in consistent with those guidelines.
Funding Sources and Conflicts of Interest: University of Colorado Movement Disorder Center Pilot Grant funded this research. The authors declare that there are no conflicts of interest relevant to this work.
Financial Disclosures for the Previous 12 Months: J.F. has received research grant support from the University of Colorado and the Mowry Fund. B.B. has received research grant support from the Dystonia Coalition (receives the majority of its support through NIH grant NS065701 from the Office of Rare Diseases Research in the National Center for Advancing Translational Science and National Institute of Neurological Disorders and Stroke), Benign Essential Blepharospasm Research Foundation, Colorado Clinical & Translational Science Institute and Center for Neuroscience, Tools4Patient, Parkinson's Foundation, and Virginia Commonwealth University School of Medicine. He is on the medical advisory board of the Benign Essential Blepharospasm Research Foundation and the National Spasmodic Torticollis Association. Brian Berman received research grant support within last 12 months from the Dystonia Coalition (through NIH grant NS065701 from the Office of Rare Diseases Research in the National Center for Advancing Translational Science and National Institute of Neurological Disorders and Stroke), Parkinson's Foundation, VCU School of Medicine, the Administration for Community Living and Dystonia Medical Research Foundation; honoraria from the MedLink Corporation and the International Parkinson and Movement Disorder Society; and consultancies from AbbVie Inc. Dr. Holden has received grant funding from the Michael J. Fox Foundation for Parkinson's Research and a loan repayment award from the National Institute of Neurological Disorders and Stroke (L30 NS103315). B. Heffernan has received a pilot grant through the Movement Disorder Center at the University of Colorado.
Acknowledgment
The authors thank the participants of this study and the University of Colorado Movement Disorders Center for providing financial support for this project. Additionally, we would like to thank Isabelle Buard, Benzi Kluger and those at the MEG Lab at the University of Colorado for providing space to conduct this study.
References
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