Changes in cerebral activity after decreased upper-limb hypertonus: an EMG-fMRI study

Magn Reson Imaging. 2010 Jun;28(5):646-52. doi: 10.1016/j.mri.2009.12.023. Epub 2010 Feb 1.

Abstract

Objective: Whereas several studies have used functional magnetic resonance imaging (fMRI) to investigate motor recovery, whether therapy to decrease post-stroke hypertonus alters central motor patterns remains unclear. In this study, we used continuous electromyography (EMG)-fMRI to investigate possible changes in movement-related brain activation in patients receiving Botulinum toxin (BoNT-A) for hand-muscle hypertonus after chronic stroke.

Methods: We studied eight stroke patients all of whom had hemiparesis and associated upper-limb hypertonus. All patients underwent an fMRI-EMG recording and clinical-neurological assessment before BoNT-A and 5 weeks thereafter. The handgrip motor task during imaging was fixed across both patients and controls. The movements were metronome paced, movement amplitude and force were controlled with a plastic orthosis, dynamometer and EMG recording. An age-matched control group was recruited from among healthy volunteers underwent the same fMRI-EMG recording.

Results: Before BoNT-A, while patients moved the paretic hand, fMRI detected wide bilateral activation in the sensorymotor areas (SM1), in the supplementary motor area (SMA) and cerebellum. After BoNT-A blood oxygenation level-dependent (BOLD) activation decreased in ipsilateral and contralateral motor areas and became more lateralized. BOLD activation decreased also in ipsilateral cerebellar regions and in the SMA.

Conclusion: Changes in peripheral upper-limb hypertonus after BoNT-A were associated to an improvement in active movements and more lateralized and focalized activation of motor areas. The clinical and EMG-fMRI coregistration technique we used to study hand-muscle hypertonus in patients receiving BoNT-A after chronic stroke should be useful in future studies seeking improved strategies for post-stroke neurorehabilitation.

MeSH terms

  • Aged
  • Arm / physiopathology*
  • Brain Mapping / methods*
  • Electromyography / methods*
  • Evoked Potentials, Motor*
  • Female
  • Humans
  • Magnetic Resonance Imaging / methods
  • Male
  • Middle Aged
  • Motor Cortex / physiopathology*
  • Movement*
  • Muscle Hypertonia / diagnosis
  • Muscle Hypertonia / physiopathology*