title: How to assess motor impairment in writer's cramp.
abstract: Writer's cramp is a task-specific hand dystonia affecting handwriting. Clinical scores such as the Arm Dystonia Disability Scale (ADDS) or Writer's Cramp Rating Scale (WCRS) as well as kinematic analysis of handwriting movements have been used to assess functional impairment in affected patients. In 21 patients with writer's cramp and healthy controls, we analyzed the kinematics of writing and cyclic drawing movements. We rated the severity of dystonia using the ADDS and WCRS and correlated the clinical scores with movement kinematics. Mean stroke frequency was significantly reduced in dystonic patients. Drawing movements showed more frequently a decrease in stroke frequency than handwriting movements. During circle drawing, mean vertical peak velocity was more variable in patients relative to controls, indicating an impaired ability to reproduce the same kinematic pattern over time. An increase in vertical writing pressure was only observed during handwriting but not during circle drawing and may reflect a compensatory effort to stabilize the pencil. Kinematic measures and individual ADDS and WCRS scores did not correlate with each other. The lack of correlation is not surprising as ADDS, WCRS, and kinematic analysis probe different aspects of motor impairment. The ADDS characterizes how dystonia affects a set of fine manual tasks, whereas the WCRS scores the manifestation of dystonia during handwriting. Therefore, the clinical scores and kinematic analysis of handwriting provide complementary insights into motor impairment. Future studies need to address which combination of clinical scores and kinematic measures are most appropriate to quantify impairment in writer's cramp.
authors.affiliation: Department of Neurology, Christian Albrechts University Kiel, Kiel, Germany. k.zeuner@neurologie.uni-kiel.de
authors.forename: Kirsten E
authors.initials: KE
authors.lastname: Zeuner
authors.forename: Martin
authors.initials: M
authors.lastname: Peller
authors.forename: Arne
authors.initials: A
authors.lastname: Knutzen
authors.forename: Iris
authors.initials: I
authors.lastname: Holler
authors.forename: Alexander
authors.initials: A
authors.lastname: Münchau
authors.forename: Mark
authors.initials: M
authors.lastname: Hallett
authors.forename: Günther
authors.initials: G
authors.lastname: Deuschl
authors.forename: Hartwig R
authors.initials: HR
authors.lastname: Siebner
mesh_terms: D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D004185:Disability Evaluation; D004421:Dystonia / Q000175:diagnosis / Q000503:physiopathology; D020821:Dystonic Disorders / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D006236:Handwriting; D006801:Humans; D008297:Male; D008875:Middle Aged; D009069:Movement Disorders / Q000175:diagnosis* / Q000503:physiopathology*; D010300:Parkinson Disease / Q000175:diagnosis / Q000503:physiopathology; D011795:Surveys and Questionnaires