title: Asymmetric corticomotor excitability correlations in early Parkinson's disease.
abstract: We studied corticomotor excitability (CE) between the more and less affected sides in early Parkinson's disease (PD) patients using transcranial magnetic stimulation (TMS). Sixteen-PD patients within the first 3 years of diagnosis were studied with single-pulse TMS over each motor cortex with intensities from 40% to 100% stimulator output. Active motor evoked potentials (MEP) and cortical silent period durations (CSP) were recorded, fitted with sigmoid curves, summarized as maximal MEP/CSP, maximal MEP/CSP slope, and intensity where MEP/CSP is half-maximal (MEP/CSP-Int50), and correlated with Unified Parkinson's Disease Rating Scale scores (UPDRS). On the more affected side, higher (worse) UPDRS scores were correlated with shorter maximal CSP (r=-0.51, P=0.046). On the less affected side, higher UPDRS scores were correlated with higher MEP-Int50 (r=0.51, P=0.043) and CSP-Int50 (r=0.54, P=0.029). For the less affected side, altered CE, as indexed by higher MEP or CSP-Int50 intensities, may contribute to early clinical symptoms. On the more affected side, increases in CE, indexed by shorter CSP, may account for a greater proportion of PD symptoms. These findings are consistent with an evolution of neurophysiologic correlates in early PD patients from a less to more symptomatic state.
authors.affiliation: Department of Neurology, David Geffen School of Medicine, University of California Los Angeles (UCLA), Los Angeles, California 90095-1769, USA. allanwu@mednet.ucla.edu
authors.forename: Allan D
authors.initials: AD
authors.lastname: Wu
authors.forename: Giselle M
authors.initials: GM
authors.lastname: Petzinger
authors.forename: Chien-Ho J
authors.initials: CH
authors.lastname: Lin
authors.forename: Myron
authors.initials: M
authors.lastname: Kung
authors.forename: Beth
authors.initials: B
authors.lastname: Fisher
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D010300:Parkinson Disease / Q000175:diagnosis* / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation