title: Interhemispheric and ipsilateral connections in Parkinson's disease: relation to mirror movements.
abstract: Mirror movements (MM) occur in early, asymmetric Parkinson's disease (PD). To examine the pathophysiology of MM in PD, we studied 13 PD patients with MM (PD-MM), 7 PD patients without MM (PD-NM), and 14 normal subjects. Cross-correlogram did not detect common synaptic input to motoneuron pools innervating homologous hand muscles in PD-MM patients. Transcranial magnetic stimulation studies showed no significant difference in ipsilateral motor-evoked potentials between PD-MM patients and normal subjects. The MM side of PD-MM patients showed a slower increase in ipsilateral silent period area with higher level of muscle contraction than the non-MM side and normal subjects. There was less interhemispheric inhibition (IHI) at long interstimulus intervals of 20 to 50 ms in PD-MM than PD-NM. IHI reduced short interval intracortical inhibition in normal subjects and PD-NM, but not in PD-MM. IHI significantly increased intracortical facilitation in PD-MM and PD-NM patients, but not in normal subjects. Our results suggest that MM in PD is due to activation of the contralateral motor cortex. PD-MM patients had reduced transcallosal inhibitory effects on cortical output neurons and on intracortical inhibitory circuits compared to PD-NM patients and controls. These deficits in transcallosal inhibition may contribute to MM in PD patients.
authors.affiliation: Division of Neurology, Department of Medicine, Toronto Western Research Institute, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Jie-Yuan
authors.initials: JY
authors.lastname: Li
authors.forename: Alberto J
authors.initials: AJ
authors.lastname: Espay
authors.forename: Carolyn A
authors.initials: CA
authors.lastname: Gunraj
authors.forename: Pramod K
authors.initials: PK
authors.lastname: Pal
authors.forename: Danny I
authors.initials: DI
authors.lastname: Cunic
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Lang
authors.forename: Robert
authors.initials: R
authors.lastname: Chen
mesh_terms: D001921:Brain / Q000503:physiopathology*; D003337:Corpus Callosum / Q000033:anatomy & histology / Q000503:physiopathology; D004576:Electromyography; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009069:Movement Disorders / Q000503:physiopathology*; D010300:Parkinson Disease / Q000503:physiopathology*; D012016:Reference Values