Geneva: Three paralysed patients have been able to walk again, thanks to precise electrical stimulation of their spinal cords via a wireless implant, Swiss scientists said.
According to the study published in the journals Nature and Nature Neuroscience, after a few months of training the patients with chronic paraplegia were able to control previously paralysed leg muscles even in the absence of electrical stimulation.
The study, called STIMO (STImulation Movement Overground), establishes a new therapeutic framework to improve recovery from spinal cord injury, said researchers from the Ecole Polytechnique Federale de Lausanne (EPFL) and the Lausanne University Hospital (CHUV) in Switzerland.
All patients involved in the study recovered voluntary control of leg muscles that had been paralysed for many years, they said.
Unlike the findings of two independent studies published recently in the US on a similar concept, neurological function was shown to persist beyond training sessions even when the electrical stimulation was turned off.
"Our findings are based on a deep understanding of the underlying mechanisms which we gained through years of research on animal models. We were thus able to mimic in real time how the brain naturally activates the spinal cord," said EPFL neuroscientist Gregoire Courtine.
"All the patients could walk using body weight support within one week. I knew immediately that we were on the right path," said CHUV neurosurgeon Jocelyne Bloch, who surgically placed the implants in the patients.
"The exact timing and location of the electrical stimulation are crucial to a patient's ability to produce an intended movement. It is also this spatiotemporal coincidence that triggers the growth of new nerve connections," said Courtine.
This study achieves an unprecedented level of precision in electrically stimulating spinal cords, researchers said.
"The targeted stimulation must be as precise as a Swiss watch. In our method, we implant an array of electrodes over the spinal cord which allows us to target individual muscle groups in the legs," said Bloch.
The new rehabilitation protocols based on this targeted neurotechnology lead to improved neurological function by allowing the participants to actively train natural overground walking capabilities in the lab for extensive periods of time, as opposed to passive training like exoskeleton-assisted stepping.
During rehabilitation sessions, the three participants were able to walk hands-free over more than one kilometer with the help of targeted electrical stimulation and an intelligent bodyweight-support system.
Moreover, they exhibited no leg-muscle fatigue, and so there was no deterioration in stepping quality, researchers said.
These longer, high-intensity training sessions proved crucial for triggering activity-dependent plasticity -- the nervous system's intrinsic ability to reorganise nerve fibres -- which leads to improved motor function even when the electrical stimulation is turned off.
