Neural Stimulation for Hand Grasp in People With Tetraplegia
Condition: Tetraplegia
MeSH terms: Quadriplegia
Study type: Interventional

Summary: 
      A selective neural stimulation as the investigators propose allows to stimulate several
      muscles via a single electrode. Neural stimulation requires less energy for muscle
      activation. In our approach, 2 electrodes will be implanted above the elbow on the median,
      the ulnar and the radial nerves. This considerably reduces the number of implanted elements
      and therefore i) the risk of infection, ii) the risk of failure, iii) the surgical risk
      through minimally invasive surgery.

      Our main hypothesis is that multipolar neural electrical stimulation of the median and the
      ulnar nerve (flexion) and the radial nerve (extension) allows:

        -  on the one hand, a selective, individualized motor activation (muscle by muscle)

        -  on the other hand, a synergistic motor activation (association of several muscles) for
           the purpose of production of functional movements.
    

Detailed description: 
      Electrical stimulation of the muscles has been used for decades in rehabilitation units
      specializing in the treatment of spinal cord injuries. It has been shown to be effective in
      building muscle and preventing muscle atrophy following spinal cord injury (SCI) or stroke.
      It can also be used to reduce spasticity and above all to promote functionally useful motor
      control. It is then a Functional Electric Stimulation (FES). In the quadriplegic person
      marked by a severe motor deficiency of the upper limbs, FES is today the only technique
      allowing to restore a functional gripping movements in the case where the active muscular
      resources below the elbows are missing or too weak to allow tendon transfer surgery.

      Like "Freehand", all the devices using FES directly stimulate the muscles (surface,
      intramuscular or epimysial electrodes) and therefore require a high number of internal
      components with a theoretical risk of infection and greater rejection. since each muscle must
      be activated via an electrode (up to 12 in the case of "FreeHand"). The investigators propose
      instead selective neural stimulation as it allows stimulating several muscles via a single
      electrode. Neural stimulation requires less energy for muscle activation. In our approach,
      three electrodes will be implanted above the elbow on the median, the ulnar and the radial
      nerves. This considerably reduces the number of implanted elements and therefore i) the risk
      of infection, ii) the risk of failure, iii) the surgical risk thanks to minimally invasive
      surgery. The procedure consisted of placing a multi-contact cuff electrode around the radial,
      ulnar or median nerves and observing the effects of electrical neural stimulation in terms of
      muscle selectivity, force produced and movement induced. In a previous study, the
      investigators already proved through acute intra operative testing (under Ethics Committee
      approval, #NCT03721861) that:

      No failure of the electrodes or of the stimulator was noted. For all of the 8 subjects, it
      was possible to selectively stimulate muscle groups to obtain the opening of the thumb and
      fingers, or the flexion of the thumb, fingers and obtaining possibly functional grip like the
      forceps with opposition of the thumb or palmar grip.

      A second feasibility study (Ethics committee registration #2016-A00711-50) with 17
      quadriplegic patients assessed the subject's ability to use voluntary contractions of sus
      lesional muscles (EMG recordings in 8 subjects) or voluntary movements of shoulders (inertial
      recordings in 9 subjects) to control the movements of a robotic hand or the triggering of an
      electrical surface stimulation of the muscles of the forearm. All of the patients managed to
      master the proposed interface after a short familiarization period.

      On the basis of the results of these two studies, the investigator wish to take an additional
      step in the development of a gripping assistance device for patients with spinal cord injury
      by proposing the implantation of three cuff electrodes with percutaneous connection on the
      arm of people with tetraplegia. The electrodes will be kept in place for a period of 1 month
      before being definitively explanted. An implanted cable will connect the electrodes to an
      external connector. A preliminary study based on the implantation of only 2 electrodes (on
      the median and the radial nerve) was conducted in 2020 in 2 patients.vNeither of the 2
      participants showed general and local comorbidity. Acceptability was optimal. None of the
      stimulation configurations generated contradictory movements. The success rate in task
      execution by the electro-stimulated hand exceeded the target of 50% (54% and 51% for patient
      1 and 2 respectively). The compliance rate of the control orders in both patients was > 90%
      using motion IMU-based detection and 100% using EMG-based detection in patient 1. These
      results support the relevance of neural stimulation of the tetraplegic upper limb with a more
      selective approach, using multi-contact epineural electrodes with 9 and 6 contact points for
      the median and radial nerve respectively.
    

Intervention name(s): Neurostimulation
Intervention type(s): Other
Intervention description(s): Implantation of 3 multicontact cuff electrodes in the upper limb of patients with tetraplegia and control of the stimulation by contralateral shoulder movements
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Tetraplegia; Neural stimulation