September 2016: Volz LJ, Rehme AK, Michely J, Nettekoven C, Eickhoff SB, Fink GR and Grefkes C. (2016) Shaping early reorganization of neural networks promotes motor function after stroke. Cerebral Cortex, 26(6), 2882-2894 10.1093/cercor/bhw034
Abstract: Neural plasticity is a major factor driving cortical reorganization after stroke. We here tested whether repetitively enhancing motor cortex plasticity by means of intermittent theta-burst stimulation (iTBS) prior to physiotherapy might promote recovery of function early after stroke. Functional magnetic resonance imaging (fMRI) was used to elucidate underlying neural mechanisms. Twenty-six hospitalized, first-ever stroke patients (time since stroke: 1–16 days) with hand motor deficits were enrolled in a sham-controlled design and pseudo-randomized into 2 groups. iTBS was administered prior to physiotherapy on 5 consecutive days either over ipsilesional primary motor cortex (M1-stimulation group) or parieto-occipital vertex (control-stimulation group). Hand motor function, cortical excitability, and resting-state fMRI were assessed 1 day prior to the first stimulation and 1 day after the last stimulation. Recovery of grip strength was significantly stronger in the M1-stimulation compared to the control-stimulation group. Higher levels of motor network connectivity were associated with better motor outcome. Consistently, control-stimulated patients featured a decrease in intra- and interhemispheric connectivity of the motor network, which was absent in the M1-stimulation group. Hence, adding iTBS to prime physiotherapy in recovering stroke patients seems to interfere with motor network degradation, possibly reflecting alleviation of post-stroke diaschisis.
As I said in my post, this is such impressive research because it’s so “cutting edge”! These researchers have investigated intermittent theta-burst stimulation that’s applied just before physiotherapy targeting upper limb recovery. What they were asking was, did this improve functional outcomes and what was the brain’s response?
They recruited 26 participants with first-ever, ischemic stroke who were all less than 2 weeks post-stroke. They excluded those with severe aphasia, apraxia and neglect. The two groups were similar in age and severity of hand function. The stimulation in combination with the physiotherapy was applied for 5 consecutive days and participants were assessed the day before and the day after. All participants received stimulation, but those in the intervention group had the stimulation applied to the ipsilesional (same side of the lesion) primary motor cortex (M1) and those in the sham group had the stimulation applied to parieto-occipital vertex.
Cortical excitability was measured in motor evoked potentials…now I know that here is where I’ll start to lose some of you…and I completely understand. The neuroplasticity literature can be really, really hard to understand, sometimes; but my advice is to simply keep reading. The more you read this literature, the more you’ll start to understand it. As the researchers state, they measured the excitability or responsiveness of the brain, and where that response occurred. Motor evoked potentials or MEP are a measure of that responsiveness – yes? Still with me?
What they found was that all patients experienced significant improvement in upper limb function, which is exactly what they would have expected. However, what they also found was that this priming approach in the group that received stimulation to the primary motor cortex (M1), “significantly enhanced recovery of grip strength compared with control stimulation in subacute stroke”. The researchers theorized that “M1-stimulation induced a network-level effect beyond the induction of synaptic plasticity,..[and this] probably contributed to the recovery of motor function”. As they go on to say, neuroplasticity does not just occur in the region around the lesion or stroke (perilesional); it occurs across the brain’s networks.
In the next few years, we are going to hear more and more about how the brain’s networks respond after damage caused by stroke and in turn, how recovery interventions impact the brain’s response at a network level. I’m so looking forward to learning more about this as I think it will start to significantly influence what we do in which patients. As always, this is just my humble opinion. To critique this evidence for yourself, please read it – it’s freely available.
PS. To understand stroke recovery, I’d suggest that you’ll need to understand the neuroplasticity literature, so, it’s worth reading it more and more. I found that over time, I started to better understand it. Well worth the effort, (in my post-script humble opinion,) if you’re prescribing and applying healthcare to people recovering from a recent stroke. (My thanks to those who read right through to here!!)
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