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Abstract
BackgroundWe hypothesized that a selective neural electrical stimulation of radial and median nerves enables the activation of functional movements in the paralyzed hand of individuals with tetraplegia. Compared to previous approaches for which up to 12 muscles were targeted through individual muscular stimulations, we focused on minimizing the number of implanted electrodes however providing almost all the needed and useful hand movements for subjects with complete tetraplegia.MethodsWe performed acute experiments during scheduled surgeries of the upper limb with eligible subjects. We scanned a set of multicontact neural stimulation cuff electrode configurations, pre-computed through modeling simulations. We reported the obtained isolated and functional movements that were considered useful for the subject (different grasping movements).ResultsIn eight subjects, we demonstrated that selective stimulation based on multicontact cuff electrodes and optimized current spreading over the active contacts provided isolated, compound, functional and strong movements; most importantly 3 out of 4 had isolated fingers or thumb flexion, one patient performed a Key Grip, another one the Power and Hook Grips, and the 2 last all the 3 Grips. Several configurations were needed to target different areas within the nerve to obtain all the envisioned movements. We further confirmed that the upper limb nerves have muscle specific fascicles, which makes it possible to activate isolated movements.ConclusionsThe future goal is to provide patients with functional restoration of object grasping and releasing with a minimally invasive solution: only two cuff electrodes above the elbow.Ethics Committee / ANSM clearance prior to the beginning of the study (inclusion period 2016–2018): CPP Sud Méditerranée, #ID-RCB:2014-A01752–45, first acceptance 10th of February 2015, amended 12th of January 2016.Trial registration(www.clinicaltrials.gov): #NCT03721861, Retrospectively registered on 26th of October 2018.
Highlights
We hypothesized that a selective neural electrical stimulation of radial and median nerves enables the activation of functional movements in the paralyzed hand of individuals with tetraplegia
In a theoretical study combined with a preclinical trial we showed that several 3D-shapings were optimal, depending on the size and location of the targeted area within the nerve, and this was almost independent of the subject, except the global scale [28]
We determined the current intensity threshold for each subject and the predetermined configurations were automatically scanned with increasing intensities following pre-computed and subject-specific ranges
Summary
We hypothesized that a selective neural electrical stimulation of radial and median nerves enables the activation of functional movements in the paralyzed hand of individuals with tetraplegia. FES was used to recover grip movements in patients with high tetraplegia as early as 1963 [10,11,12] These devices used either intramuscular or epimysial electrodes, requiring one electrode for each muscle involved in the targeted movement. The second implant was mostly dedicated to elbow and shoulder movements with 2 intramuscular electrodes and the use of cuff electrodes limited to the best contact response among the 4 against a global reference leading to a monopolar like stimulation that is not the most selective one. The FreeHand device was commercialized but was limited by the complexity of the surgery due to the high number of muscle electrodes implanted over the arm/forearm/hand; the surgery was estimated to last 5 h with an access to all targeted muscles [15] and it is not commercialized since 2001
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