title: Different mechanisms may generate sustained hypertonic and rhythmic bursting muscle activity in idiopathic dystonia.
abstract: Despite that deep brain stimulation (DBS) of the globus pallidus internus (GPi) is emerging as the favored intervention for patients with medically intractable dystonia, the pathophysiological mechanisms of dystonia are largely unclear. In eight patients with primary dystonia who were treated with bilateral chronic pallidal stimulation, we correlated symptom-related electromyogram (EMG) activity of the most affected muscles with the local field potentials (LFPs) recorded from the globus pallidus electrodes. In 5 dystonic patients with mobile involuntary movements, rhythmic EMG bursts in the contralateral muscles were coherent with the oscillations in the pallidal LFPs at the burst frequency. In contrast, no significant coherence was seen between EMG and LFPs either for the sustained activity separated out from the compound EMGs in those 5 cases, or in the EMGs in 3 other cases without mobile involuntary movements and rhythmic EMG bursts. In comparison with the resting condition, in both active and passive movements, significant modulation in the GPi LFPs was seen in the range of 8-16 Hz. The finding of significant coherence between GPi oscillations and rhythmic EMG bursts but not sustained tonic EMG activity suggests that the synchronized pallidal activity may be directly related to the rhythmic involuntary movements. In contrast, the sustained hypertonic muscle activity may be represented by less synchronized activity in the pallidum. Thus, the pallidum may play different roles in generating different components of the dystonic symptom complex.
authors.affiliation: The Movement Disorders and Neurostimulation Unit, Charing Cross Hospital and Division of Neuroscience and Mental Health, Imperial College London, 11L15 East Block, Charing Cross Hospital, Fulham Palace Road, London W6 8RF, UK. x.liu@ic.ac.uk
authors.forename: Xuguang
authors.initials: X
authors.lastname: Liu
authors.forename: John
authors.initials: J
authors.lastname: Yianni
authors.forename: Shouyan
authors.initials: S
authors.lastname: Wang
authors.forename: Peter G
authors.initials: PG
authors.lastname: Bain
authors.forename: John F
authors.initials: JF
authors.lastname: Stein
authors.forename: Tipu Z
authors.initials: TZ
authors.lastname: Aziz
mesh_terms: D000328:Adult; D000368:Aged; D046690:Deep Brain Stimulation; D020821:Dystonic Disorders / Q000503:physiopathology* / Q000628:therapy*; D004576:Electromyography / Q000379:methods; D005260:Female; D007839:Functional Laterality; D005917:Globus Pallidus / Q000503:physiopathology / Q000528:radiation effects; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology* / Q000528:radiation effects; D010507:Periodicity