Impaired performance of patients with writer's cramp in complex fine motor tasks.

OBJECTIVE: Writer's cramp (WC) is a task-specific focal dystonia. WC is characterized by involuntary contractions of muscles of the hand and arm during handwriting, resulting in impaired writing with exaggerated finger forces. The generalization of symptoms to other fine motor tasks is widely discussed. The aim of the study was to determine affected fine motor aspects with an extensive testing battery. METHODS: Twelve people with WC and twelve healthy controls were examined. Performance in the Jebsen-Taylor Hand Function Test, Nine-Hole-Peg Test and 2-point discrimination was evaluated. To analyze object manipulation skills, we examined grip forces, temporal measures and other aspects of force control during (1) lifting actions with variations of weight and surface (2) cyclic movements (3) visuomotor tracking (4) fast force changes and (5) grip strength. In addition, correlation between the dependent variables of the fine motor tasks and the handwriting deficits was assessed. RESULTS: WC patients had impaired performance in the visuomotor tracking task (root mean square error (RMSE), p = 0.03 and time lag, p = 0.05) and the fast force changes (frequency, p = 0.01). There were no statistically significant group differences in the other tasks. We found a correlation between the RMSE of the tracking task and the time needed to write the test sentence (r = 0.643, p = 0.01). CONCLUSION: WC patients revealed abnormalities in complex fine motor performance in tasks with high demands on coordination and visual components, specifically in tracking and fast force changes. SIGNIFICANCE: This suggests a deficit in visuomotor integration, coordination and cognitive aspects related to movement processing particularly with respect to low forces. These insights may prove useful in the development of targeted training approaches.

Significance of finger forces and kinematics during handwriting in writer's cramp.

Muscular hyperactivity during handwriting, irregular and jerky scripts, as well as awkward and slowed pen movements are the cardinal symptoms of writer's cramp. Accordingly, impaired kinematics and increased force have been reported in writer's cramp. However, the relationship between these symptoms has rarely been investigated. In addition, measurements of finger forces have been restricted to the vertical pen pressure. In the present study, the pen of a graphic tablet was equipped with a force sensor matrix to measure also the grip force produced against the pen barrel despite highly variable pen grips of the patients. Kinematics of writing movements, vertical pen pressure, and grip force were compared in 27 patients with writer's cramp and normal control writers during writing of a test sentence. As expected, all measures revealed a significantly worse writing performance in the patients compared to the control subjects. Exaggerated forces were more frequent than abnormal kinematics, and evidenced by prolonged movement times and reduced writing frequencies. Correlations were found neither between kinematics and force measures nor between the two forces. Interestingly, patients relaxed the grip force during short periods of non-writing by the same relative amount as control subjects. The finding of a large heterogeneity of performances patterns in writer's cramp may reflect the variability of dystonic symptoms as well as the highly variable compensatory strategies of individual patients. Measurements of finger force and in particular of the grip force are valuable and important descriptors of individual impairment characteristics that are independent of writing kinematics.

Effects of modified pen grip and handwriting training on writer's cramp.

OBJECTIVE: To evaluate the use of a modified pen grip and subsequent handwriting training in patients with writer's cramp (WC). DESIGN: Handwriting performance with normal and modified pen grip was examined once in healthy controls and repeatedly in patients with WC (2 baseline tests before training, directly after training, after a 3-month follow-up). SETTING: Ambulatory care for motor writing disorders. PARTICIPANTS: Patients with WC (n=26) and healthy controls (n=14). INTERVENTION: Seven sessions of handwriting training with various motor exercises were conducted by an occupational therapist. During training, the patients always used a modified pen grip (stabilized between index and middle finger). MAIN OUTCOME MEASURES: Writing frequency and fluency, grip force on the pen, writing pressure, Fahn dystonia scale, visual analog scales for impairment and pain. RESULTS: Patients with WC showed increased writing pressure and grip force before training. Using the modified pen grip caused in both patients with WC and controls a decrease in pressure and grip force. Handwriting training resulted in a further improvement of both parameters in patients with WC. Grip force reduction remained stable over follow-up. CONCLUSIONS: Results suggest that patients with WC benefit from the use of the modified pen grip in combination with handwriting training.

Auditory grip force feedback in the treatment of Writer's cramp.

STUDY DESIGN: Pre-post, single-group. INTRODUCTION: Writer's cramp (WC) is a focal dystonia causing impairments in daily life. Behavioral treatment approaches have been shown to improve handwriting performance, though outcomes remain sub-optimal. PURPOSE OF THE STUDY: To examine the effects of the handwriting training and auditory grip force feedback in seven patients with WC. METHODS: Handwriting performance was examined before and after treatment. Writing frequency, fluency, and pressure were recorded with a digitizing tablet and grip forces during handwriting were recorded. Subjective writing performance and pain were rated on visual analog scales. RESULTS: The treatment resulted in significant reductions in writing pressure and pain, while writing performance was significantly improved. CONCLUSIONS: Patients in this study with WC, who exhibit grip force and pressure problems, benefit from feedback-supported handwriting training.

Modified pen grip in the treatment of Writer's Cramp.

Writer's Cramp (WC) is a focal, action-related dystonia, which induces hypertonic co-contractions and severely impairs handwriting. One behavioral treatment approach is the handwriting training developed by Mai and Marquardt (1999), [Mai, N., & Marquardt, C. (1999). Schreibtraining in der neurologischen Rehabilitation. In EKN-Materialien für die Rehabilitation. Dortmund: Borgmann] which includes among various motor exercises the use of a modified pen grip (stabilized between index and middle finger). This pen grip has proven particularly successful in clinical practice. The current study aims at elucidating the immediate effects of the modified pen grip on writing in 23 WC patients and 11 healthy controls. All participants wrote a sentence with their usual and also with the modified pen grip. Movement and pressure were recorded with a digitizing tablet. Pressure, movement time for the whole sentence, script size and writing fluency were analyzed. When writing with their usual pen grip, pressure in the WC patients was elevated, and writing speed was decreased compared to healthy controls. Changing over to the modified pen grip reduced the pressure significantly in WC patients and controls, but left other aspects of their writing unaffected. This shows that the use of the modified pen grip is an effective way to normalize pen pressure in WC patients, thereby providing the best conditions for the training of speed and fluency.