Computerized 22-channel stimulator for limb movement.

The Nucleus multichannel implantable hearing prosthesis (Nucleus Ltd., Sydney, Australia) has been modified by computer programming (MOCO, Inc., Scituate, Mass.) into a 22-channel neural stimulator for use in functional electrical stimulation (FES). Individual or multiple channels can be sequenced and adjusted for their individual pulse amplitude, width and frequency so that activation of single and multiple nerves can be achieved. Anesthetized rabbits' sciatic nerve branches (lateral and medial) were stimulated to produce single, or co-contraction at the ankle and simultaneous bilateral joint movements. The spiral (helix) electrode was also found suitable in these experiments. In planning for the stimulator's use in paraplegic subjects, information was obtained for human lower extremity peripheral nerves. In 9 patients undergoing lower extremity amputation, threshold and maximal levels of stimulation plus nerve diameters were obtained on 21 nerves. The design for the wearable ambulation unit to control the 22-channel stimulator and electrode tresses with helix electrodes has been completed.