The aim of the PREHENS-STROKE study is to propose a functional replacement device to restore grip capacities in patients with hemiparesis after stroke, unable to actively open the hand to seize objects. The main objective is to evaluate the impact of the use of a self-controlled prehension neuroprosthesis on the ability to perform a standardized grasping task, consisting of grasping, relocating and releasing a glass (palmar grasp) or a spoon (key-pinch), compared to a condition without the use of the prehension neuroprosthesis.

Stroke is the leading cause of motor impairment acquired after 40 years. Of the affected patients, 50% do not recover active finger extension and there is no satisfactory solution for functional recovery of the grip in these patients. The use of wearable exoskeletons to improve the grip is limited by their size and cost. An alternative is the use of functional electrical stimulation of the grasping muscles, named prehension neuroprosthesis, well developed in the spinal cord injured patient. In the adult hemiplegic patient, only about ten studies concerned the functional impact of a prehension neuroprosthesis, which have shown potential to perform a correct hand opening linked with a significant functional gain. Nevertheless, one of the major problems concerns the definition of the optimal modalities to control the prehension neuroprosthesis, modalities which until now have proved unsuitable for post-stroke patients: an open-loop control with manual triggering of the neuroprosthesis (press-button type) is not suitable with daily living use; control with the contralateral upper-limb is also not suitable for everyday use where bimanual tasks are required; and finally, the use of the residual voluntary electromyographic activity of the targeted muscle limits the opening of the fingers and the reliability of the control by promoting the occurrence of spastic cocontractions of the flexors of the fingers.

In this context, the present project proposes to evaluate the functional contribution of a closed-loop controlled prehension neuroprosthesis that will restore an extension of the fingers and the thumb in order to improve the grip function.

Each patient is evaluated 5 times during visits lasting between 1h30 and 2 hours. Patients are already admitted to standard care for a period of at least 5 consecutive days in the Rehabilitation Center. The visit (Day 1) will include the patient and collect the Action Arm Research Test (ARAT) and Upper Limb Performance Assessment (ULPA) scores achieved with the inactive prehension neuroprosthesis. The visit T1 (day 2) will select the preferred control mode of the neuroprosthesis. The visit T2 (day 3) and T3 (day 4) will allow learning and training in the use of the neuroprosthesis. The visit T4 (day 5) will evaluate the functional impact of the neuroprosthesis: the patients will perform the standardized primary and secondary gripping tasks with the activated or inactivated neuroprosthesis, then the ARAT and ULPA with activated neuroprosthesis, and finally the Psychosocial Impact of Assistive Devices Scale and the Device subscale of the Quebec User Assessment of Satisfaction with Assistive Technology questionnaire will be completed. The end of the visit T4 corresponds to the end of the patient's inclusion in the research protocol.

Inclusion Criteria:

• Concerning the study population: Paresis of an upper limb from a single ischemic or hemorrhagic, hemispheric or brainstem stroke, as evidenced by brain imaging (CT or MRI); Stroke more than one month old; Impossibility to actively expand the fingers 2 to 5 (opening of the hand) to intentionally grab an empty glass (identical to the material used for the Action Research scale Arm Test), with a palmar grip (cylindrical grip), while the subject can hold the glass passively placed in the hand and/or the thumb to voluntarily grab the handle of a tablespoon (flat, like a wrench) with a key-grip (identical to that of the Wolf Motor Function Test), while the subject can hold the spoon previously placed passively between thumb and index; Ability to sit on a chair at least during 1h30.
• Concerning legislative aspects: Free, informed and written consent signed by the participant and the investigator (at the latest on the day of inclusion and before any investigation required by the research); Affiliate or beneficiary of the French health insurance system; The person is of age (at least 18 years old); Women and men are included; The patient is available for a follow-up of 5 days as part of his hospitalization performed as part of routine care.

Exclusion Criteria:

• Concerning the study population: The person is parturient, or is breastfeeding; The person is pregnant, the diagnosis being guided by the interrogation (date of the last menstruation, desire of pregnancy, contraception) and possibly confirmed by a blood test (beta hCG); Musculotendinous retractions or joint stiffness of the fingers and wrist preventing passive opening of the hand sufficient to perform at least one of the functional tasks evaluated; Limitation of the approach which does not make it possible to carry out the task of gripping in front of the trunk, the subject sitting; Upper limb pain limiting achievement of the primary standardized grasping task; Major sensory disorders corresponding to a sub-score Somesthesia of the modified Erasmus Nottingham Sensory Assessment French version (EmNSA-F) for the upper limb <10/44; Severe aphasia with aphasia severity scale of the Boston Diagnostic Severity Aphasia Examination, indicating that there may be a clear decrease in verbal fluency or ease and speed of understanding, with no significant limitation expression or communication; Unilateral spatial negligence highlighted with the bells test if the difference between the omissions in the left and right fields is greater than or equal to 6; Extensor digitorum communis muscle and/or pollicis extensor longus muscle not stimulable with the neuroprosthesis, i.e. a sufficient extension of fingers and/or thumb for grasping tasks is not obtained with an electrical stimulation well supported by the patient.
• Concerning the associated pathologies: The person is carrying a pacemaker; Presence of unstable epilepsy; Presence of unstable cardio-vascular disease (coronary heart disease, major hypertension, heart failure); Presence of a dermatological problem against indicating the application of surface electrodes.
• Concerning associated treatments: The person should not receive an injection of botulinum toxin in the upper limb during the period of inclusion in the protocol, or in the 30 days prior to inclusion.
• Concerning legislative aspects: The person is participating in another research protocol including an exclusion period still in progress; The person is under the protection of justice or guardianship; The person refuses to sign the consent; It is not possible to give the person informed information and to make sure of the subject's compliance due to impaired physical and/or psychological health.