Primary motor cortex excitability during recovery after stroke: implications for neuromodulation

'May' is not useful at all for what survivors need to recover. Doing a half-assed job doesn't help survivors one bit. 

Primary motor cortex excitability during recovery after stroke: implications for neuromodulation

Cathy M. Stineara,b, Matthew A. Petoea,b, Winston D. Byblowb,c,*a Department of Medicine, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand b Centre for Brain Research, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand c Department of Sport & Exercise Science, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand a r t i c l e i n f o  Article history: Received 14 March 2015 Received in revised form 27 May 2015 Accepted 22 June 2015 Available online xxx Keywords: Stroke Sub-acute Upper limb Transcranial magnetic stimulation Motor cortex

Abstract 

Background:  Non-invasive brain stimulation techniques may be useful adjuvants to promote recovery after stroke. They are typically used to facilitate ipsilesional cortical excitability directly, or indirectly by suppressing contralesional cortical excitability and reducing interhemispheric inhibition from the contralesional to ipsilesional hemisphere. However, most of the evidence for this approach comes fromstudies of patients at the chronic stage of recovery.
Hypothesis:  We hypothesized that corticomotor excitability and interhemispheric inhibition wouldinitially be asymmetric, with greater interhemispheric inhibition from contralesional to ipsilesional M1. We also hypothesized that balancing of corticomotor excitability and interhemispheric inhibition would be associated with greater improvements in paretic upper-limb impairment and function.
Methods:  We conducted a retrospective analysis of longitudinal data collected from 46 patients during the  first six months after stroke. Transcranial magnetic stimulation was used to measure rest motor threshold, stimulus-response curves, and ipsilateral silent periods from the extensor carpi radialis muscles of both upper limbs. Analyses of variance and linear regression modeling were used to evaluate the effect of time on corticomotor excitability and interhemispheric inhibition in both hemispheres, and associations between these effects and improvements in paretic upper-limb impairment and function.
Results:  All participants had subcortical damage and only two had motor cortex involvement. As ex-pected, ipsilesional corticomotor excitability was initially suppressed and increased over time, and this increase was associated with improved upper-limb impairment and function. However, interhemisphericinhibition was symmetrical and stable over time, and there was no evidence for a decrease in contralesional corticomotor excitability.
Conclusions:  Neuromodulation interventions applied during spontaneous recovery may be more beneficial if they facilitate ipsilesional corticomotor excitability directly.