Functional neuromuscular stimulation neuroprostheses for the tetraplegic hand.

Functional neuromuscular stimulation (FNS) of the C5 and C6 tetraplegic upper extremity has been shown to be a valid clinical tool for restoring controlled movement in the paralyzed hand. The current clinical system consists of a shoulder position transducer controlling an external microprocessor-based stimulator, which excites paralyzed muscle via the peripheral nerve using percutaneous leads or a multichannel, implantable stimulator. Tendon transfer surgery of paralyzed but innervated muscle may augment the neurologically deficient upper extremity by allowing the substitution of stronger motors or the addition of new motors where flaccid paralysis (dennervation) eliminates the usual muscle from a grasp pattern. Sensory feedback in the form of machine state and cognitive information can be provided to the normally innervated C5 dermatome skin by subcutaneous electrodes. C5- and C6-level tetraplegics using FNS can independently perform single-hand manipulative tasks at a level similar to that of subjects with intact C7 roots, although they lack the elbow control.