Roles of Lesioned and Nonlesioned Hemispheres in Reaching Performance Poststroke.
Rachael M Harrington, Evan Chan, Amanda K Rounds and 4 others
PMID 31858870WHAT IT FOUND
Briefly disrupting a nonlesioned premotor area slowed affected-arm reaching in chronic stroke patients with severe arm impairment.
In milder impairment, disrupting lesioned motor cortex slowed reaching. This was a brain-stimulation experiment, not a therapy trial.
Key findings
01In the severe group, perturbing the nonlesioned hemisphere's dorsal premotor cortex slowed reaching more than perturbing the nonlesioned hemisphere's primary motor cortex.
02In the mild group, perturbing the lesioned hemisphere's primary motor cortex slowed reaching more than perturbing the lesioned hemisphere's dorsal premotor cortex.
03In the mild group, perturbing the nonlesioned hemisphere's dorsal premotor cortex produced a small faster movement time.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
Only 20 patients were studied, and the supplied text does not state how many were in each impairment group. The study measured immediate movement-time changes during a laboratory reaching task, not recovery of arm function or daily-life outcomes. TMS was used to disrupt activity, not to deliver a rehabilitation intervention, so it does not show that stimulation helps patients. For many severe patients, the lesioned hemisphere primary motor cortex site could not be confirmed by motor evoked potentials and was placed by mirror-image anatomy. Double-pulse TMS affects a region within a network, so a slowing effect may reflect connected areas as well as the targeted site. The reaching task did not require finger movement, so the findings may not apply to grasp or hand tasks. The supplied text does not give the actual magnitude of the movement-time changes, so it is hard to judge how large the effects were.
Declared interests
The authors declared no conflict of interest. The supplied publication types indicate NIH extramural and non-U.S. government research support.
The easy way to misread this
Do not conclude that TMS to the nonlesioned premotor area improves reaching. The study temporarily disrupted activity and measured slower movement times. It did not test facilitation, rehabilitation, or functional recovery.