A Functional MRI Study On Writer's Cramp

Background: Writer's cramp is the most common task-specific idiopathic focal dystonia with incompletely understood pathophysiology. It is characterized by excessive cocontractions of agonist and antagonist hand and forearm muscles during writing .Recently, a lot of research had been done to find out the etiopathogenesis of the dysfunction. These findings are still debated. Therefore ,a further research is necessary.Objective In this study ,we performed a functional magnetic resonance imaging (fMRI) study with block design to find out which brain areas activity correlates with writer's cramp and provide a possible frame of reference for further etiology treatment.Method We use fMRI block design . The stimulate form is "stimulate — rest — stimulate" ,which is designed by Presentation software. Ten right-handed patients with unilateral writer's cramp and ten age- and gender-matched control subjects participated in this study. Subjects were scanned at 1.5 Tesla magnetic resonance imaging scanner while they were performing three visually instructive tasks with MR Vision 2000: (1) suppositional writing; (2) writing with finger; (3) writing with pencil. Image date were co-registered to correct head motion, spatial normalized , deconverlution and then analyzed for group wise of patients vs. controls, using AFNI software. We also got functional activated maps for "writing with pencil" minus "writing with finger" and "writing with pencil" minus "suppositional writing" with general linear analyzed. Finally, we got the interesting area by observing the match of stimulating and area activated.Result Compared with controls, we found patients with writer's cramp showed greater activation of contra lateral basal ganglion (esp. putamen), ipsilateral cerebellar hemisphere, and contralateral sensorimotor, supplementary motor , premote, primary sensory cortex in the task of writing with pencils than controls. There is no obvious difference in the task of writing with finger between two groups. And we find these difference also exsit in the functional activated maps for "writing with pencil" minus "writing with finger", while the activation of subcortical area and insula in controls disappeared.Conclusion These results indicates that the dysfunction of basal ganglion and subcortical-cortical loop might play a role in the pathophysiology of writer's cramp. And the change of motor cortex, sensory cortex and thalamus maybe is secondary.