Doctors implanted electrodes in the spine of three paralyzed patients, thanks to which they can now stand, walk, swim, ride a bicycle or canoe, and more. The development is a complex of flexible electrodes controlled wirelessly via a tablet. The patient selects the type of activity on the tablet, after which the corresponding signals are sent through the electrodes to the spinal cord, activating the movement of the limbs.
The technology is called Epidural electrical stimulation (EES). The electrodes are placed in the space between the spine and the spinal cord, after which, in accordance with the given command, the nerve fibers are selectively activated. Thanks to this, it is possible to imitate the natural signals of the nervous system entering the limbs from the brain. EES has shown itself very well in matters of rehabilitation and restoration of motor functions in paralyzed patients. For example, in 2017, a study was published in Scientific Reports showing how a patient was able to move their legs again after using EES along with a special training program.
The researchers took the already existing experience with EES as a basis and modernized it. Two programs were developed - with the help of one, the scientists slightly revised the location of the electrodes, with the help of the second, they provided a quick setting of stimulation commands for specific activities that reproduced the natural activation of motor neurons during various activities.
The image above shows a flexible base (bar) with 16 electrodes, developed by the authors during the study. On the left is the new bar, on the right is the previous version, which was used in 2017. Before installation, doctors do CT and MRI to personalize the location of the electrodes. On their basis, a three-dimensional anatomical atlas of the spine was created, where the electrodes are planned to be installed - a section of the spinal column from T10 to L5.
After that, the obtained data was run through 15 computational models. They showed that additional personalization of the electrode placement is required, and added more data to the simulation about the movement of the legs and the processes that occur in response to a signal to the legs from the nervous system. In total, three people participated in the study, and for each of them a personalized atlas was compiled with its own model. As practice has shown, personalized models showed significantly higher rates than general ones. To enable neurons to be controlled remotely, the authors supplemented the Activa RC implantable pulse generator with wireless communication modules. Activa RC was implanted into the abdominal cavity and electrodes were connected to it.
During the experiments, the extensor muscles were supplied with a pulsed current with a frequency of 20 Hz, the flexors - 100 Hz. At first, the patient was in a supine position to facilitate fine-tuning. The researchers then began experimenting with firing combinations of neurons to recreate the natural firing patterns of neurons during walking. Remarkably, on the first day, all three participants were able to walk on the treadmill on their own. After additional optimization of the model, the gait became more confident already on the third day. All patients moved with the support of special devices such as walkers.
In the end, three study participants completed a 5-month neurorehabilitation program during which EES allowed them to stand, walk, and perform a wide range of exercises four or five times a week. The authors developed a simplified software interface for them, which made it possible to switch between activity-dependent stimulation programs and fine-tune the key parameters of these programs. Auxiliaries have been fitted with ergonomically designed buttons that launch EES programs at will.
All participants gradually regained full weight-bearing capacity, resulting in the ability to stand independently (using a walker). One participant even regained the ability to climb stairs and navigate difficult terrain. Thanks to EES and exercise, patients regained muscle mass in paralyzed limbs, which significantly improved the results of therapy.
The results of the study can be read in .epdf - Activity-dependent spinal cord neuromodulation rapidly restores trunk and leg motor functions after complete paralysis.
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