The myth of the 'unaffected' side after unilateral stroke: Is reorganisation of the non-infarcted corticospinal system to re-establish balance the price for recovery?

S. Graziadio, L. Tomasevic, G. Assenza, F. Tecchio, J. A. Eyre

Research output: Contribution to journalArticle

Abstract

Background: Bilateral changes in the hemispheric reorganisation have been observed chronically after unilateral stroke. Our hypotheses were that activity dependent competition between the lesioned and non-lesioned corticospinal systems would result in persisting asymmetry and be associated with poor recovery. Methods: Eleven subjects (medium 6.5. years after stroke) were compared to 9 age-matched controls. The power spectral density (PSD) of the sensorimotor electroencephalogram (SM1-EEG) and electromyogram (EMG) and corticomuscular coherence (CMC) were studied during rest and isometric contraction of right or left opponens pollicis (OP). Global recovery was assessed using NIH score. Findings: There was bilateral loss of beta frequency activity in the SM1-EEGs and OP-EMGs in strokes compared to controls. There was no difference between strokes and controls in symmetry indices estimated between the two corticospinal systems for SM1-EEG, OP-EMG and CMC. Performance correlated with preservation of beta frequency power in OP-EMG in both hands. Symmetry indices for the SM1-EEG, OP-EMG and CMC correlated with recovery. Interpretation: Significant changes occurred at both cortical and spinomuscular levels after stroke but to the same degree and in the same direction in both the lesioned and non-lesioned corticospinal systems. Global recovery correlated with the degree of symmetry between corticospinal systems at all three levels - cortical and spinomuscular levels and their connectivity (CMC), but not with the absolute degree of abnormality. Re-establishing balance between the corticospinal systems may be important for overall motor function, even if it is achieved at the expense of the non-lesioned system.

Original languageEnglish
Pages (from-to)168-175
Number of pages8
JournalExperimental Neurology
Volume238
Issue number2
DOIs
Publication statusPublished - Dec 2012

Keywords

  • Corticomuscular coherence
  • Corticospinal
  • EEG
  • EMG
  • Homeostatic plasticity
  • Motor
  • Recovery
  • Reorganisation
  • Stroke
  • Symmetry

ASJC Scopus subject areas

  • Neurology
  • Developmental Neuroscience

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