title: Increased variability in spiral drawing in patients with functional (psychogenic) tremor.
abstract: Increased variability is a characteristic clinical and physiologic feature of functional (psychogenic) tremor. In this study, we use computerized spiral analysis to show that the variability of a motor task is a quantifiable characteristic of functional tremor. We compare functional tremor patients to phenomenologically similar dystonic tremor patients and to normal controls. We used the spiral severity score, a measure that does not incorporate spiral tightness, as a marker of spiral drawing performance, and inter-spiral tightness variability (based on the 25-75%(ile) range in tightness across ten spirals) to evaluate the effects of functional tremor on drawing spirals. The spirals of 74 participants: 22 functional tremor, 21 dystonic tremor, and 31 normal controls were analyzed. Spiral severity was higher in both tremor groups compared to controls, but did not differentiate them. Inter-spiral variability, however, was higher in the functional tremor group compared to both other groups. Thus, spiral analysis captures variability of a motor task and may be used as an objective test for functional tremor. The effect of functional tremor in other motor tasks should be investigated.
authors.affiliation: Department of Neurology, Clinical Motor Physiology Laboratory, Columbia University Medical Center, New York, NY, USA.
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Hess
authors.affiliation: Department of Neurology, Clinical Motor Physiology Laboratory, Columbia University Medical Center, New York, NY, USA.
authors.forename: Annie W
authors.initials: AW
authors.lastname: Hsu
authors.affiliation: Department of Neurology, Clinical Motor Physiology Laboratory, Columbia University Medical Center, New York, NY, USA.
authors.forename: Qiping
authors.initials: Q
authors.lastname: Yu
authors.affiliation: Department of Neurology, Beth Israel Medical Center, New York, NY, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Ortega
authors.affiliation: Department of Neurology, Clinical Motor Physiology Laboratory, Columbia University Medical Center, New York, NY, USA. Electronic address: sp31@columbia.edu.
authors.forename: Seth L
authors.initials: SL
authors.lastname: Pullman
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D020821:Dystonic Disorders / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009048:Motor Skills / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D015203:Reproducibility of Results; D014202:Tremor / Q000503:physiopathology*
keywords: Dystonia; Functional; Movement disorders; Psychogenic; Spiral analysis; Spirography; Tremor