Department of Exercise Sciences


Corticospinal tract integrity correlates with knee extensor weakness in chronic stroke survivors

Sangeetha Madhavan, Chandramouli Krishnan, Arun Jayaraman, William Z. Rymer, James W. Stinear
Published in Clinical Neurophysiology 122 (2011) 1588-1594


Introduction

Muscle weakness develops rapidly after stroke, adversely affecting motor performance, and contributing to reduced functional ability. While the contributions of structural and functional alterations in skeletal muscle to post-stroke weakness have been well described, it is not clear if there is a relationship between motor pathway integrity, measured using both radiological and electrophysiological techniques, and post-stroke muscle weakness.

Aim

This study sought to determine the role of corticospinal tract (CST) integrity on knee extensor weakness in chronic stroke survivors.

Method (Figure 1)

  • Participants: nine chronic stroke subjects with radiologically documented ischaemic cortical and/or subcortical lesions. 
  • Knee extensor strength and activation was performed at 90o of knee flexion using an interpolated triplet technique. 
  • CST integrity was evaluated using data obtained from Diffusion Tensor Imaging and transcranial magnetic stimulation (TMS)
Madhavan_Figures

 

 

 

 

 

 

 

 

Results

  • Recordings in nine stroke subjects indicated substantial knee extensor weakness and activation deficits in the paretic legs of the stroke survivors (Figure 2). 
  • Regression analysis revealed that asymmetry in CST integrity was strongly related to between-leg differences in knee strength (Figure 3A) where knee strength was lower in subjects with greater CST damage.

Interpretation

This study potentially provides an understanding of the mechanisms underlying post-stroke muscle weakness at the structural level of motor pathways. The results of this study indicate that both structural and physiological integrity of the CST are important for optimal quadriceps strength after stroke. We found significant voluntary activation deficits in both the paretic and non-paretic legs indicating that bilateral neural impairments that are commonly reported early after stroke do not recover and persist years after stroke.

The findings of this study have meaningful implications to clinicians and researchers who focus on improving muscle performance after stroke.

Acknowledgements

This work was supported in part by K01HD056216, R21HD059287, NIDRR H133F090009, and NIDRR H133E070013. The authors would like to thank T. George Hornby, PT, PhD for providing access to his laboratory facility for data collection.