Spinal cord neuromodulation restores trunk and leg function… : Neurology Today

By Mark Morane

March 3, 2022

Article in brief

An optimized spinal cord stimulation approach quickly restored independent walking and other motor activities, such as cycling and swimming, in three men with complete sensorimotor paralysis within a single day. Spinal cord injury and rehabilitation experts said the results, while very promising, need to be replicated in other trials.

Timeline of sit-to-stand, swimming, leg press, and motorized exercises through activity-specific stimulation programs.

Epidural Electrical Stimulation (EES) that targets specific dorsal roots involved in leg and trunk movement during specific activities enabled three people with complete sensorimotor paralysis to stand, step, cycling, swimming and controlling core movement with support in a single day, according to an article published online Feb. 7 in natural medicine.

Ongoing neurorehabilitation has led to improvement sufficient to restore these activities in community settings, opening a realistic pathway to support daily mobility with SEA in people with spinal cord injury, wrote lead author Gregoire Courtine. , PhD, and colleagues at the Center for Neuroprosthetics and Brain. Institute, Ecole Polytechnique Fédérale Suisse and the department of clinical neurosciences of the University Hospital of Lausanne in Switzerland, and other institutions.

They noted that although the three participants could move independently, they did not regain their natural movements. Still, this recovery was enough to perform various activities for long periods of time. Additionally, two participants were able to modulate leg movements during the EES, suggesting that the stimulation stimulated residual descending pathway signals, according to the report.

In an interview with neurology today, co-author Robin Demesmaeker, PhD, head of the clinical/therapeutic development division at the Defitech Center for Interventional Neurotherapies (NeuroRestore) in Lausanne, said that this achievement marks a refinement of previous spinal cord SEA methods in three ways. : Larger implantable paddle probe with an electrode arrangement targeting all of the dorsal roots involved in leg and lower trunk movement; software developed to facilitate the design and execution of activity-specific stimulation sequences that recruit the right muscles at the right time; and the use of personalized computer models based on magnetic resonance imaging (MRI), functional MRI, and computed tomography to guide electrode placement and mimic each patient’s specific nerve-muscle configuration as closely as possible.

“We know from previous clinical work that when we stimulate the spinal cord, and in particular the dorsal root entry areas where sensory fibers enter the spinal cord, we can recruit muscles,” said he declared. “At the same time, we know that if we look at the innervation of different leg and trunk muscles, some muscles are innervated by certain nerves, other muscles by other nerves.”

“Furthermore, every movement has a time sequence of muscle activation. If you stimulate the right dorsal roots in the right time sequence, we can selectively recruit those muscle groups for a specific activity.

He and his colleagues demonstrated the proof of concept in a 2018 paper in Nature in patients who still had muscle movement. “Now we’re going a step further with the electrodes placed in a way that optimizes the outcome for patients with complete sensory motor paralysis.” MRI imaging of the spinal cord allowed the team to build an “atlas” of 15 computer models associated with different possible configurations of the spinal cord and nerves to “customize” electrode placement as close to each as possible. of the three patients.

Expert commentary

The experts who reviewed the document for neurology today agreed that this was a potentially significant advance for patients with severe spinal cord injury. However, few centers worldwide currently perform this type of sophisticated SEA, and the technique and results need to be replicated in larger studies with patients with a range of spinal cord injuries.

“Over the past ten years, a number of small experiments using epidural stimulation of the dorsal roots in the lumbar region in people with severe cervical or thoracic spinal cord injury have revealed that if there are enough pathways residual supraspinal cords, you can get people to bear weight and take action,” explained Bruce H. Dobkin, MD, FAAN, professor of clinical neurology in the Neurorehabilitation Program at UCLA.

“The authors refined the technique by stimulating the dorsal roots specific to the flexor and extensor muscles of the lower paraspinals and legs to create sequential step-like movements,” he said. “The fact that they could replicate the stimulation for patients to pedal or swim motions tells you that they really had excellent muscle group control.”

Dr. Dobkin said the best candidates for this type of therapy are people who have residual neural pathways – sensations or a bit of voluntary movement but are unable to make them useful. “But the authors of this paper extended that to people with no clinically apparent sensorimotor control,” he said. “With the right timing and stimulation sequences, it appears that they too can be made to walk slowly with a walker for distances of at least 300 feet at seemingly low energy cost. Two of the three participants studied had enough latent supraspinal input to the motor pools to even make voluntary corrections to their steps.

Michael E. Selzer, MD, PhD, FAAN, professor of neural sciences at Temple University’s Lewis Katz School of Medicine, agreed. “I think it’s a realistic technology if further testing on a larger number of patients shows that the claims are valid: that the new paddle probe design and improved software to activate nerve roots individual electrodes work better than the previously available electrode array and software. ,” he said neurology today. “The stimulator is small enough to be implanted in the body and the control module is wireless.”

“Patients should have preserved nerve pathways between the brain and spinal cord below the injury,” Dr. Selzer said. “The system acts as a sort of amplifier for the motion control system. But there must be something to amplify. If the injury is anatomically complete, the system probably won’t work. The patient must always use the control module, which makes it very difficult for quadriplegic patients. »

“I suspect most users would be paralyzed in the legs, but not the arms,” Dr. Selzer continued. “Furthermore, although the system can generate motor patterns, it does not restore sensation or sensory feedback to the brain, so a patient would not be able to balance without additional assistance, such as a walker. .”

Dr. Selzer noted that the authors acknowledged that the movements were not perfectly normal. “Activation of individual dorsal roots can be imperfect due to variability in patient anatomy, so it may be necessary to customize paddle leads and even increase the number of electrodes in a lead. More importantly again, each muscle is innervated by multiple segments, and each segment contributes to the activity of multiple muscles, so even with perfect control of the dorsal root stimulation pattern, it may not be possible to obtain patterns normal engines with this technology.

Dr Demesmaeker said the team is now looking to apply the technology to other conditions linked to spinal cord injury, such as the wide variability in blood pressure in patients. And they want to test the technique in patients much sooner after spinal cord injury. “At present, the patients have been out for at least a year since their injury, and some for eight or nine years. This begs the question: what might happen if you applied this technique shortly after injury to exploit the window of neuroplasticity? »

The technique seems to be far from being widely available in the clinic. But the natural medicine paper marks a milestone in hope for patients with severe spinal cord injury.

Dr Dobkin said: “These neuromodulation techniques are advancing in ways that I never would have imagined 20 years ago.”

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