The aim of the study is to investigate the effectiveness of a new rehabilitation technology for paralysis that occurs after stroke or spinal cord injury. The research will jointly use a prototype neurorehabilitation orthosis, in which a robotic device moves a paralyzed arm at the command of a non-invasive brain-computer interface to perform a game life-like task augmented using a virtual-reality display, as well as an electrical stimulation device that activates the spinal cord and/or muscles of the paralyzed arm.

Investigators expect that a portion of the patients participating in the study will have an improvement in arm mobility by the end of the study.

Participants who express their special written consent will have venous blood tests conducted three times for subsequent analysis of lipid biomarkers, in order to further evaluate the effectiveness of rehabilitation methods based on biochemical analysis.

The aim of the study is to investigate the effectiveness of a new rehabilitation technology for paralysis that occurs after stroke or spinal cord injury. The research will jointly use a prototype neurorehabilitation orthosis, in which a robotic device moves a paralyzed arm at the command of a non-invasive brain-computer interface to perform a game life-like task in virtual reality (for example, aiming a hand-held virtual toy gun at a target), as well as an electrical stimulation device that activates the spinal cord and/or muscles of the paralyzed arm.

The study is carried out to collect data on the role of central and spinal mechanisms in the plasticity of neuronal circuits that determine the effect of combined spinal neurostimulation and robotic rehabilitation under the control of non-invasive neural interfaces in patients in early and late rehabilitation period after acute cerebrovascular accident and in patients after trauma of the cervical and upper thoracic spinal cord.

The study will use two technologies - neural interfaces and transcutaneous electrical stimulation of the spinal cord. Neural interfaces are a rapidly developing area at the intersection of medicine, neuroscience, biology, engineering, robotics, physics, mathematics, and materials science, which aims to reproduce and supplement brain functions and correct these functions in cases of neurological lesions. The possibility of using neural interfaces for the treatment of neurological disorders, including disorders resulting from spinal cord and brain injuries, epilepsy, strokes, and neurodegenerative diseases, such as Parkinson's disease, has been demonstrated.

Transcutaneous spinal cord stimulation (tSCS) is a method for non-invasive control of the activity of human spinal neural networks used to restore locomotor functions after spinal cord injury (SCI). The published research results show that tSCS modulates the activity of not only spinal but also cortical neuronal networks.

It is expected that the use of tSCS in conjunction with the use of neural interfaces will increase the effectiveness of neural interfaces for the rehabilitation of neurological lesions, including stroke, and SCI.

Biochemical monitoring will be applied for objective monitoring of the physiological conditions of patients, such as the physiological state of muscle tissue and the level of neuropathic pain. This method is based on the identification of metabolic and lipid compounds associated with physiological parameters in blood plasma samples, and the subsequent use of these compounds as biomarkers to assess the effectiveness of rehabilitation techniques carried out using the neural interface, as well as to optimize them. This monitoring will be helpful for each individual patient, as it will provide additional information about the course of rehabilitation. Blood sampling and follow-up testing will only be performed for patients who gave their written consent for this procedure. The analysis results will be stored in anonymized form.

The study participants will receive up to 12 rehabilitation procedures, each lasting about one hour, within two-four weeks. During the procedure, the activity of the brain (electroencephalogram) and muscles (electromyogram) will be recorded using non- invasive electrodes placed on the scalp and body. Also, during the study, electrical stimulation will be performed with non-invasive electrodes placed on the body.

During the exercise, participants focus their attention on the target of movement and/or imagine that their arms perform a movement. If the task is completed correctly, the robot will move the arm towards the target. This movement can additionally be accompanied with functional electrical stimulation using disposable electrodes glued to the skin on the back and/or the arms. The strength of the stimulation will be adjusted so as not to cause discomfort. Participants will be randomly assigned to groups, and participants in some groups will receive tSCS and some will not.

On the day of inclusion in the study, as part of Visit 1 (screening), anamnesis will be collected, and there will be performed assessment on the study scales, BCI testing, an EMG study with registration of muscle activity (rhomboid, pectoralis major, biceps, deltoid) and / or visual determination of tSCS thresholds.

After Visit 1, patients in the study groups will undergo 12 procedures of BCI-driven robotic rehabilitation accompanied by tSCS.

Visit 2 is carried out the next day after the end of the study to assess the study scales and conduct the EMG study described above.

Visit 3 is carried out one month after the end of the study to assess the study scales and conduct an EMG study.

Throughout the study, adverse events (AEs) will be monitored. Sessions will be held daily in 6/1 or 5/2 mode, in a rehabilitation room or at patients' homes, with a session duration of about 60 minutes. The duration of Visits 1-3 will be approximately 2 hours.

Investigators expect that a portion of the patients participating in the study will have an improvement in voluntary arm movements by the end of the study.

Patient data will be recorded and stored in anonymized form. Only research team members will have access to this information. If it is necessary to publish individual results on study scales, diagnoses, anamnesis, and age of participants, participants will be identified with codes. The study data is supposed to be stored for 10 years on a protected file storage with limited access.

Criteria for inclusion in the study of patients:

1. Signed written informed consent.
2. Men or women aged 18 to 60 years after a first occurred acute cerebrovascular accident or in the recovery period after injury of the cervical and upper thoracic spinal cord.
3. Early or late rehabilitation period of acute cerebrovascular accident by the type of ischemic stroke or the consequences of SCI in the late recovery period
4. Diagnosis of "acute ischemic cerebrovascular accident", or a condition after spinal cord injury at the C3-C7 level, moderate or high severity ASIA A and ASIA B, according to the discharge summary, MRI or CT.
5. For groups of patients with stroke: the degree of severity of paresis of the upper limb from 3 points to 0 (according to the 6-point MRC muscle strength scale https://cpd-program.ru/methods/mrc.htm)
6. The patient's ability and willingness to comply with the requirements of this protocol.
7. Expressed patient motivation for rehabilitation.

Inclusion criteria for healthy volunteers:

1. Signed written informed consent.
2. Men or women between the ages of 18 and 40
3. Absence of somatic and psychiatric diseases (according to the reports of the subject and according to the examination of a medical specialist before the start of the study)
4. Ability and willingness to comply with the requirements of this protocol.

Exclusion Criteria:

1. Severe cognitive impairment (<10 points on the Montreal Cognitive Assessment Scale).
2. The score on the Hamilton scale is above 18 points.
3. The rating on the Rankin scale is higher than 4 points.
4. Concomitant diseases that cause a decrease in muscle strength or an increase in muscle tone in the upper limbs (for example, cerebral palsy, brain damage as a result of trauma) or rigidity (for example, Parkinson's disease, contracture).
5. Late stages of arthritis or significant limitation of range of motion.
6. The absence of a part of the upper limb due to amputation caused by various reasons.
7. Any medical condition, including mental illness or epilepsy, that may affect the interpretation of the test results, the conduct of the test, or the safety of the patient.
8. Alcohol abuse, medical marijuana use, or light drug use in the previous 12 months.
9. Use of experimental drugs or medical devices within the previous 30 days prior to Visit 1.
10. Inability to comply with research procedures, according to the researcher.
11. The severity of the patient's condition according to the data of the neurological or somatic status, which does not allow full rehabilitation
12. Visual acuity less than 0.2 in the weakest eye according to the table of visual acuity of Sivtsev.
13. Unstable angina and / or heart attack during the previous month
14. History of stroke (for patients with spinal cord injury) or recurrent stroke (for patients with acute cerebrovascular accident).
15. Uncontrolled arterial hypertension.
16. Ataxia.
17. Pacemaker and / or other implanted electronic devices.
18. Taking muscle relaxants.
19. Peripheral neuropathy.
20. Concomitant diseases in the stage of exacerbation or decompensation, requiring active therapy.
21. The presence of allergic reactions and / or other skin lesions at the place of application of the heart rate electrodes at the time of the study.
22. Acute urinary tract infections.
23. Acute thrombophlebitis.
24. All forms of epilepsy.
25. Benign and malignant neoplasms.

Only selected research team members will have access to individual participant data. The research team will not be sharing or releasing any IPD to third parties.

Patients rehabilitation outcomes will be assessed by blinded assessors. In Neva Arm some patients will receive sham tSCS, with gradient decrease of the stimulation intensity from threshold level to 0 during one minute, as described in PMID 29335430 and PMID: 31996455