摘要Background Writer's cramp is a type of task specific idiopathic focal dystonia and has an incompletelyunderstood pathophysiology. The present study utilized functional magnetic resonance imaging (fMRI) toinvestigate what type of brain activity correlates with writer's cramp and its physiological mechanism.Methods Ten patients with writer's cramp were age and gender matched with ten healthy control subjects in ablock design. Subjects were scanned by fMRI while performing three consecutive, visually instructive, tasks withMR Vision 2000: (1) suppositional writing, (2) writing with finger and (3) writing with a pencil. Data wasanalysed using AFNI software for groups of patients and controls.Results The patients with writer's cramp showed significant activations of contralateral basal ganglion(especially the putamen), motor cortex (primary sensorimotor cortex, supplementary motor cortex, premotorcortex) and ipsilateral cerebellar hemisphere in writing with a pencil compared with controls; whereas there wasno obvious difference between patients and controls during writing with finger. Furthermore, these differencesexist in the subtractive activated maps for "writing with a pencil" minus "writing with finger" of patients, whenthe activation of subcortical area and insula in controls disappeared.Conclusions Abnormal activations of contralateral basal ganglion, motor cortex and ipsilateral cerebellarhemisphere of the patients with writer's cramp suggest dysfunction of basal ganglion and subcortical-corticalloop might play a pathophysiological role in writer's cramp.