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Angelo Quartarone, MD,1* Sergio Bagnato, MD,1,2 Vincenzo Rizzo, MD,1 Francesca Morgante, MD,1 Antonino Sant’Angelo, MD,1 Domenica Crupi, MD,1 Marcello Romano, MD,3 Corrado Messina, MD,1 Alfredo Berardelli, MD,2 and Paolo Girlanda, MD1

1Department of Neurosciences, Psychiatric and Anaesthesiological Sciences, University of Messina, Messina, Italy 2Department of Neurological Sciences, and Istituto Neurologico Mediterraneo Neuromed IRCCS, Pozzilli (IS), University of Rome La Sapienza, Rome, Italy
3Divisione di Neurologia, Ospedale Villa Sofia, Palermo, Italy

Abstract

Motor imagery (MI) is the mental rehearsal of a motor act without overt movement. Using transcranial mag- netic stimulation (TMS), we tested the effect of MI on corti- cospinal excitability in patients with writer’s cramp. In 10 patients with writer’s cramp and 10 healthy controls, we ap- plied focal TMS over each primary motor area and recorded motor evoked potentials (MEPs) from contralateral hand and arm muscles while participants imagined a tonic abduction of the index finger contralateral to the stimulated hemisphere. In healthy controls and patients, the MEP amplitude in the relaxed first dorsal interosseus muscle (FDI) showed a muscle-specific increase during MI; however, the increase was less pronounced in patients than in healthy controls. In addition, in patients but not in controls, the MEP amplitude also increased in hand and forearm muscles not involved in the imagined movement. This abnormal spread of facilitation was observed in the affected and unaffected upper limb. MI of simple hand movements is less efficient and less focussed in patients with writer’s cramp than it is in normal subjects. © 2005 Movement Disorder Society
Key words: writer’s cramp; motor imagery; transcranial magnetic stimulation (TMS); dystonia