Anastasia Shulga, Helsinki University Hospital, Helsinki, Finland

Long-term paired associative stimulation for incomplete spinal cord injury patients

Funded in: 2019, 2020, 2021, 2022

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Problem: How to enhance learning and adaptation mechanisms inherent to the central nervous system

Target: Driving signal transmission between upper and lower motoneuronal pools towards a more effective state and a better motor performance

Goal: Bring Paired associative stimulation (PAS) from experimental stage into actual clinical practice


Two types of neurons are essential for voluntary movement. Upper motor neurons transmit the signals from the brain to the spinal cord, and lower motor neurons from spinal cord to the muscles. After spinal cord injury the connections between these neuronal populations are impaired and voluntary intention to move is not transmitted to the muscles effectively.

Paired associative stimulation (PAS) is a technique where noninvasive transcranial magnetic brain stimulation (TMS) is synchronized with peripheral nerve electrical stimulation (PNS). TMS activates the upper and PNS the lower motor neurons. Learning and adaptation mechanisms inherent to the central nervous system dictate that simultaneously active neuronal populations develop strengthened connections. Through this mechanism, PAS presumably drives the signal transmission between the upper and lower motoneuronal pools towards a more effective state, leading to better motor performance in patients with incomplete spinal cord injury.

The scientists have developed their own, clinically feasible modification of PAS, and applied it to chronic SCI patients as a long-term treatment with successful outcomes. They show that PAS induces clinically relevant and long-term therapeutic effects. The applicability of this method at the subacute stage of SCI is yet unexplored. It is plausible that subacute patients would benefit even more, since there is greater potential for adaptive changes right after injury, before development of severe muscle loss.

During funding period, the team will further develop the method, and, most importantly, apply it at the subacute stage of SCI. They will conduct double-blind randomized sham-controlled study enrolling in total 20 subacute tetraplegic patients. They will investigate the impact of upper limb PAS on hand function and, ultimately, on the independence of patients in daily life activities.

The ultimate goal of the project is to bring their approach from the experimental stage into actual clinical practice.