Cerebral activation patterns in patients with writer's cramp: a functionalmagnetic resonance imaging study

Functional MRI (fMRI), visualizing changes in cerebral blood oxygenation, h as to date not been performed either in patients with writer's cramp or in healthy subjects during writing. We compared the cerebral and cerebellar ac tivation pattern of 12 patients with writer's cramp during writing with a g roup of 10 healthy subjects performing the same tasks over 30-s periods of rest or writing. Sixty echo planar imaging multislice datasets were analyse d using SPM96 software. Data were analysed for each subject individually an d groupwise for patients vs. controls. Healthy subjects showed a significan t activation of the ipsilateral dentate nucleus, contralateral cerebellar h emisphere, contralateral primary sensorimotor cortex, and contralateral pre central gyrus during writing. Patients with writer's cramp showed significa ntly greater activation of the ipsilateral cerebellar hemisphere than contr ols. Also the activation in the primary sensorimotor cortex extended furthe r caudally and anteriorly towards the premotor association area. Activation was observed in the thalamus during writing only among the patients. Our r esults indicate an increased basal ganglia output via the thalamus to the m otor and premotor cortical areas in dystonia patients and support the notio n of disinhibition of the motor cortex leading to cocontractions and dyston ic postures.