# Cervicomedullary motor evoked responses in individuals with severe chronic hemiparesis post-stroke: a feasibility study

## TL;DR

This study explores a new method to assess motor recovery potential in stroke patients who show no response to traditional brain stimulation techniques.

## Contribution

The study introduces cervicomedullary electrical stimulation as a feasible alternative to transcranial magnetic stimulation for assessing motor pathways in post-stroke individuals.

## Key findings

- Most participants classified as MEP− with TMS were found to be CMEP+ in multiple upper limb muscles.
- Cervicomedullary electrical stimulation is feasible in individuals with severe chronic hemiparesis post-stroke.
- The findings suggest potential for clinical translation and further exploration of post-stroke recovery mechanisms.

## Abstract

Understanding the neural mechanisms underlying upper limb motor recovery after stroke remains a significant challenge in rehabilitation research. It has been proposed that individuals who show no motor-evoked potential (MEP) response to transcranial magnetic stimulation (TMS) and are thus classified as MEP negative (MEP−) have limited potential for recovery in part due to damage of the corticospinal pathway. In this study, we investigate how individuals categorized as MEP− with TMS respond to stimulation of the corticospinal pathway at a subcortical level. We describe the methodology for eliciting MEPs by using cervicomedullary electrical stimulation (CMEP) in post-stroke individuals with severe upper limb hemiparesis. MEP status (+/−) of the more affected arm was assessed using TMS and cervicomedullary electrical stimulation in stroke survivors with severe upper extremity hemiparesis. While most of the participants were classified as MEP−, all individuals were categorized as CMEP+ in the biceps brachii, extensor carpi radialis, and first dorsal interosseous muscles. Importantly, we report the first testing of CMEPs in a small cohort of individuals with stroke. This technique is feasible in this population and has potential for application in clinical translation settings. Our findings provide a foundation for future studies to replicate and expand upon this approach, enabling the exploration of new hypotheses related to post-stroke rehabilitation and recovery.