GDF15 - A potential novel biomarker of cognitive impairment in cervical dystonia.

Introduction: Cervical dystonia (CD) is a chronic movement disorder characterized by motor symptoms and a spectrum of non-motor features, including cognitive difficulties, which may affect quality of life. To date, no biomarker exists to identify or monitor cognitive impairment in CD. Growth differentiation factor 15 (GDF15) has been associated with cognitive decline in several neurodegenerative diseases and movement disorders, providing a rationale for its investigation in CD. This study aimed to evaluate whether plasma GDF15 concentrations are associated with cognitive performance in individuals with CD and to assess examine the potential of GDF15 as a biomarker of cognitive decline in CD. Methods: Plasma GDF15 levels were measured in patients with CD before and after botulinum toxin (BoNT) treatment and compared with healthy controls. Correlations between GDF15 concentration, cognitive performance (MoCA total and domain scores), and clinical characteristics-including age, disease duration, and TWSTRS motor severity-were analyzed using Spearman's and Pearson's coefficients. Results: GDF15 concentrations were significantly higher in individuals with CD compared with healthy controls. However, GDF15 levels showed no association with age, disease duration, symptom severity, or treatment response, and remained stable following botulinum toxin administration. No correlations were found between GDF15 and global cognitive performance, with the exception of a correlation with the visuospatial MoCA sub score. Discussion: While GDF15 concentrations were elevated in CD, they did not demonstrate consistent relationships with clinical features or cognitive outcomes. These findings suggest that GDF15 cannot currently be considered a reliable biomarker of cognitive impairment in CD. Given the limited sample size, this study should be regarded as preliminary.