title: Abnormal plasticity of the sensorimotor cortex to slow repetitive transcranial magnetic stimulation in patients with writer's cramp.
abstract: Previous studies demonstrated functional abnormalities in the somatosensory system, including a distorted functional organization of the somatosensory cortex (S1) in patients with writer's cramp. We tested the hypothesis that these functional alterations render S1 of these patients more susceptible to the "inhibitory" effects of subthreshold 1 Hz repetitive transcranial magnetic stimulation (rTMS) given to S1. Seven patients with writer's cramp and eight healthy subjects were studied. Patients also received rTMS to the motor cortex hand area (M1). As an outcome measure, short-latency afferent inhibition (SAI) was tested. SAI was studied in the relaxed first dorsal interosseous muscle using conditioning electrical stimulation of the index finger and TMS pulses over the contralateral M1. Baseline SAI did not differ between groups. S1 but not M1 rTMS reduced SAI in patients. rTMS had no effects on SAI in healthy subjects. Because SAI is mediated predominantly at a cortical level in the sensorimotor cortex, we conclude that there is an abnormal responsiveness of this area to 1 Hz rTMS in writer's cramp, which may represent a trait toward maladaptive plasticity in the sensorimotor system in these patients.
authors.affiliation: Department of Neurology, University of Hamburg, Hamburg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bäumer
authors.forename: Cüneyt
authors.initials: C
authors.lastname: Demiralay
authors.forename: Ute
authors.initials: U
authors.lastname: Hidding
authors.forename: Rosalia
authors.initials: R
authors.lastname: Bikmullina
authors.forename: Rick C
authors.initials: RC
authors.lastname: Helmich
authors.forename: Silke
authors.initials: S
authors.lastname: Wunderlich
authors.forename: John
authors.initials: J
authors.lastname: Rothwell
authors.forename: Joachim
authors.initials: J
authors.lastname: Liepert
authors.forename: Hartwig R
authors.initials: HR
authors.lastname: Siebner
authors.forename: Alexander
authors.initials: A
authors.lastname: Münchau
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001931:Brain Mapping; D020821:Dystonic Disorders / Q000473:pathology* / Q000503:physiopathology*; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009433:Neural Inhibition / Q000528:radiation effects; D009473:Neuronal Plasticity / Q000528:radiation effects*; D011601:Psychophysics; D011930:Reaction Time / Q000187:drug effects; D012684:Sensory Thresholds / Q000528:radiation effects; D012867:Skin / Q000294:innervation; D013003:Somatosensory Cortex / Q000503:physiopathology* / Q000528:radiation effects; D050781:Transcranial Magnetic Stimulation