WSC 2025 | Findings from the Phase I RETRAIN trial: transcutaneous electrical stimulation in ischemic stroke

This is a single-center prospective study in the UK, and this is on monitoring the effect of transcutaneous functional electrical stimulation of common peroneal nerve on cerebral hemodynamics in patients with ischemic stroke. So this study is a Phase I feasibility study where the primary objective was to investigate in stroke patients the impact of functional electrical stimulation, specifically transcutaneous lateral stimulation of the common peroneal nerve, which is a standard of care in venous thromboembolism prevention. So we evaluated the effect of this on brain hemodynamics at different stimulation levels and at three different postural positions. The primary aim was to identify the optimal stimulation level and the postural position for the best response of cerebral hemodynamics. That is with functional stimulation versus baseline, no stimulation, with regard to the changes in the total hemoglobin concentration, which is related to the cerebral blood volume. So what we found is, so this study we enrolled 18 ischemic stroke patients, and this was an observational study. And what we found in this small group of patients is that the semi-supine and the sitting positions were the best for the cerebral hemodynamic response to this common peroneal nerve transcutaneous electrical stimulation. Now, since this was a small group of patients, so we also ran a model-based analysis. So we used an open-source model, which is the Kitware’s pulse physiology model, or a similar model. And we modeled these different positions and found further insights. So what we found is that there is a role of the heart in the effect of the stimulation-related muscle contraction leading to the facilitation of venous return towards the brain hemodynamics. And also what we found is that there are two aspects to it. Since the common peroneal nerve is a mixed nerve, so there is essentially an efferent, so the motor fibers, which when you stimulate leads to the contraction of the muscles and that facilitates mechanically the venous return. That’s the return of blood back to the heart. But also there are sensory fibers. These are afferent fibers and stimulating them also has an effect on the brain. So in the study, we didn’t specifically delineate the two effects. However, that’s something that we have to focus in the future. So that kind of led to this insight from the model-based analysis of the data that we presented at the World Stroke Congress. So currently, what we are doing is we are now in the Phase II. So like I said, the Phase I is a feasibility to kind of understand and to find the optimal parameters for the Phase II study, which is essentially a comparison between this transcutaneous electical stimulation of the common peroneal nerve versus intermittent pneumatic compression so that’s mechanical compression of the muscle again leading to the venous return and the effect of these two on the cerebral hemodynamics. So yes that’s like Phase II which is the ongoing study currently.

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