Asymmetric corticomotor excitability correlations in early Parkinson's disease

Allan D. Wu*, Giselle M. Petzinger, Chien Ho J. Lin, Myron Kung, Beth Fisher

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)1587-1593
Number of pages7
JournalMovement Disorders
Issue number11
StatePublished - Aug 15 2007
Externally publishedYes


  • Cortical excitability
  • Motor evoked potentials
  • Parkinson's disease
  • Silent period
  • Transcranial magnetic stimulation

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology

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