title: Altered dorsal premotor-motor interhemispheric pathway activity in focal arm dystonia.
abstract: Given the possible role of dorsal premotor cortex (PMd) in the pathophysiology of dystonia, we used transcranial magnetic stimulation (TMS) methods to study PMd and PMd-primary motor cortex (M1) interactions in patients with focal arm dystonia. Here, we tested the connectivity between left PMd and right M1 as well as the intracortical excitability of PMd in 11 right-handed patients with focal arm/hand dystonia and nine age-matched healthy controls. The results showed that excitability of the inhibitory connection between PMd and M1 was reduced in patients, but there was no significant difference to healthy subjects in the excitability of the facilitatory connection. A triple stimulation technique in which pairs of TMS pulses are given over PMd and their interaction measured in terms of the effect on the baseline PMd-M1 connection failed to reveal the usual pattern of interaction between the pairs of PMd stimuli. Indeed, the results in patients were similar to those seen in a group of young healthy subjects after the excitability of PMd had been changed by pretreatment with high-frequency rTMS. We suggest that reduced transcallosal inhibition from the PMd may be involved in the altered pattern of abnormal muscle contractions of agonists and antagonists (overflow).
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, Queen Square, London, United Kingdom.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Koch
authors.forename: Susanne
authors.initials: S
authors.lastname: Schneider
authors.forename: Tobias
authors.initials: T
authors.lastname: Bäumer
authors.forename: Michele
authors.initials: M
authors.lastname: Franca
authors.forename: Alexander
authors.initials: A
authors.lastname: Münchau
authors.forename: Binith
authors.initials: B
authors.lastname: Cheeran
authors.forename: Miguel
authors.initials: M
authors.lastname: Fernandez del Olmo
authors.forename: Carla
authors.initials: C
authors.lastname: Cordivari
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Rounis
authors.forename: Carlo
authors.initials: C
authors.lastname: Caltagirone
authors.forename: Kailash
authors.initials: K
authors.lastname: Bhatia
authors.forename: John C
authors.initials: JC
authors.lastname: Rothwell
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001132:Arm / Q000503:physiopathology*; D020821:Dystonic Disorders / Q000175:diagnosis / Q000503:physiopathology*; D004568:Electrodiagnosis; D019054:Evoked Potentials, Motor; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009433:Neural Inhibition; D009434:Neural Pathways / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation