Possible Contributions of Ipsilateral Pathways From the Contralesional Motor Cortex to the Voluntary Contraction of the Spastic Elbow Flexors in Stroke Survivors: A TMS Study.
Yen-Ting Chen, Shengai Li, Craig DiTommaso and 2 others
PMID 30672773WHAT IT FOUND
In mild-to-moderate stroke, brain stimulation of the uninjured motor cortex produced extra elbow flexor force during light contraction, associated with spasticity, not weakness.
It did not appear to contribute to voluntary elbow flexion strength.
Key findings
01During 10% MVC tasks, stroke subjects showed greater TMS-induced force increment (15.49% ± 17.70%) than healthy subjects (1.01% ± 0.46%).
02In stroke subjects, higher reflex torque was associated with greater TMS-induced force increment (R2 = 0.52, p = 0.03), but weakness was not (R2 = 0.008, p = 0.82).
03Normalized MEP amplitude on the resting opposite biceps was larger during 60% MVC than during 10% and 30% MVC, with no significant group difference.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The healthy and stroke groups were not age-matched: healthy adults averaged 30.5 years and stroke patients averaged 65.3 years. The sample was small: 11 healthy adults and 10 stroke patients. One stroke subject was excluded from the correlation analysis because they could not relax during passive stretch. The study did not include stroke survivors with severe impairment or severe spasticity. No neuronavigation was used to guide TMS, although the researchers repeatedly checked the hotspot. Ipsilateral EMG responses were not analyzed; the authors state the induced force was small and EMG bursts were captured only in some patients.
Declared interests
The authors reported no competing interests and no financial benefits to the authors.
The easy way to misread this
Do not read the extra force increment at 10% MVC as evidence that contralesional pathways improve voluntary elbow flexion. The increment was associated with reflex torque, not weakness, and the study did not show that it contributed to voluntary strength.