Thanks to innovative high-frequency electrical stimulation aimed at reducing muscle spasticity, two patients with paralysis caused by spinal cord injuries have shown improvement in rehabilitation efforts to regain walking capabilities.
Recent research indicates that stimulating the spinal cord electrically holds potential for restoring walking abilities post-spinal cord injury. However, for patients experiencing muscle spasms, the effectiveness of these stimulation protocols is often limited due to the erratic nature of the spasticity-related muscle stiffness. Nearly 70% of individuals with spinal cord injuries are affected by muscle spasticity.
Researchers from EPFL, Università San Raffaele, and Scuola Sant’Anna have made significant strides in tackling and alleviating muscle spasticity in patients with incomplete spinal cord injuries. They have employed high-frequency electrical stimulation to the spinal cord, which helps to mitigate the irregular muscle contractions. This novel high-frequency approach allows patients dealing with spasticity to engage in rehabilitation methods that were once unavailable to them, yielding impressive clinical results. These findings are reported in the latest issue of Science Translational Medicine.
“Our research reveals that when high-frequency spinal cord stimulation is combined with traditional continuous low-frequency stimulation, it proves effective during rehabilitation following a spinal cord injury, leading to a reduction in muscle stiffness and spasms in paralyzed patients while also assisting them in movement,” states Silvestro Micera, a professor at EPFL’s Neuro X Institute and Scuola Sant’Anna.
“This method is a safe and effective surgical option that presents new possibilities for treating patients with severe spinal cord injuries. We plan to broaden its applications to various clinical conditions over the upcoming months. We sincerely appreciate the trust that our patients have placed in us,” adds Pietro Mortini, who leads the Neurosurgery and Stereotactic Radiosurgery Unit at IRCCS Ospedale San Raffaele in Milan and is a full professor of Neurosurgery at the Vita-Salute San Raffaele University.
Electrical stimulation of the spinal cord serves as an indirect method to activate the motor neurons responsible for muscle movements. This is because sensory neurons located in the back of the spinal cord interact with the motor neurons. In cases of muscle spasticity, these spinal sensory-motor circuits become overly reactive. The spinal cord typically demonstrates a natural sensitivity to stimuli, which is beneficial for quick reflexes; however, this sensitivity is usually regulated by the brain, which helps inhibit the motor circuits. Patients with spinal cord injuries lose these inhibitory signals from the brain. By stimulating the motor circuits indirectly, the research team discovered that high-frequency stimulation of the spinal cord can artificially and safely regulate this over-sensitivity without causing discomfort to the patients.
During the clinical trial at San Raffaele Hospital, led by Mortini and Micera, Simone Romeni, the study’s primary author and a researcher at EPFL and Università San Raffaele, introduced the concept of high-frequency stimulation inspired by prior research involving high-frequency kilohertz blocks of motor circuits using peripheral nerve stimulation.
“At this moment, we can only hypothesize that high-frequency stimulation functions like a kilohertz block that inhibits muscle spasticity,” says Micera.
“The clinical results from the two patients suggest that incorporating high-frequency stimulation may significantly reduce muscle stiffness and spasms in paralysis cases. Further experiments are necessary to validate the potential of this approach,” concludes Mortini.
