Functional and organic dystonia : a psychological and kinematic study

Newby, Rachel Elizabeth

Abstract

Since David Marsden’s studies on dystonia, it has generally been considered a disorder of the basal ganglia. His ideas steadily supplanted psychogenic models of dystonia, which held sway for much of the 20th century. Yet dystonia still sits in a borderzone between neurology and psychiatry. Patients with organic dystonia have elevated rates of psychopathology, and can be difficult to distinguish from those with functional dystonia (FD). Diagnostic criteria for FD with heavy psychological emphasis have poor inter-rater reliability, and a significant minority of patients with functional movement disorders (FMDs) have normal scores on psychological scales. The purpose of this study was to explore the psychological and kinematic character of these two subtypes of dystonia, with a view to developing better diagnostic criteria.

Thirty-three patients with organic dystonia, 13 with FD and 29 healthy controls were recruited. Self-rating questionnaires for anxiety and depression, obsessive-compulsion, fatigue, pain and depersonalisation were completed by subjects. Several finger tapping tasks—freestyle, with and without geste, and metronomeguided—were performed whilst subjects wore electromagnetic sensors on thumb and index finger. Separable components of movement (such as rhythm, speed and amplitude) were derived from a comparison of the coordinates of each sensor.

Patients with organic and FD could not be reliably distinguished according to any of the psychological or kinematic variables assessed. Those with FD had higher scores across all self-rated psychological scales, compared to healthy controls, whereas patients with organic dystonia displayed elevated scores for depression and pain only. A higher proportion of patients with FD (39%) than organic dystonia (10%) had ‘moderate’ to ‘extreme’ obsessive-compulsive symptoms. In organic dystonia, movements were slower and more halting. Both dystonia groups displayed reduced maximal opening deceleration.

These findings suggest there is significant overlap between functional and organic dystonia, with a commonality in both their motor and psychological characteristics.

Citation

Newby, R. E. (2019). Functional and organic dystonia : a psychological and kinematic study. (Thesis). Hull York Medical School, the University of Hull and the University of York. Retrieved from https://hull-repository.worktribe.com/output/4221709

• Thesis Type: Thesis
• Deposit Date: Aug 1, 2019
• Publicly Available Date: Feb 23, 2023
• Keywords: Medicine
• Public URL: https://hull-repository.worktribe.com/output/4221709
• Additional Information: Hull York Medical School, The University of Hull and The University of York
• Award Date: Jan 1, 2019