Multielectrode spiral cuff for selective stimulation of nerve fibres.

In this paper we present the modelling, design, and initial experimental testing of a nerve cuff multielectrode system for selective stimulation of fibres in superficial peripheral nerve trunk regions which is capable of making a selective activation of multiple muscles. The developed multielectrode nerve cuff consists of 14 platinum stimulating electrodes embedded within a self-curling sheet of biocompatible insulation, exhibiting a spiral transverse cross-section. The spiral shape of the system is such that the number of stimulating electrodes which can be utilized depends on the diameter of the stimulated nerve. Nerves with a greater diameter automatically make use of more electrodes than thin ones. The development was based on results obtained by a histological examination of the peripheral nerves which were planned to be stimulated, and on models of excitation of myelinated nerve fibres. The modelling objectives were to determine the electric field that would be generated within a nerve trunk by a specific electrode. Moreover, the extent of initial excitation of the nerve fibres within the superficial region of the dog sciatic nerve elicited by a certain discrete stimulating electrode was predicted. For this purpose a calculation of activating function for six positions where the nerve fibres were supposed to lie within the longitudinally dissected sciatic nerve was performed. In two acute experiments on the sciatic nerve of the dog the objective was to characterize the effectiveness of the multielectrode system in monopolar selective stimulation of the superficial regions, innervating the gastrocnemius and tibialis anterior muscle. A selectivity preliminary tested by measuring the myoelectric activity of the gastrocnemius and tibialis anterior muscle after 2 months showed good results in both animals.

Implantable stimulator for selective stimulation of the common peroneal nerve: a preliminary report.

We present details of the modelling, design, and experimental testing of an implantable system with a monopolar half-cuff electrode for selective stimulation of fibres within certain superficial regions of the human common peroneal nerve which is capable of making a selective activation of muscles, thus contributing to strong dorsal flexion and moderate eversion of the hemiplegic foot. The development of the cuff electrode was based partly on data obtained from histological examination of human common peroneal nerves, and from previously described models of excitation of myelinated nerve fibres. The modelling objectives were to determine the electric field that would be generated within the deep peroneal branch of the nerve by a monopolar half-cuff electrode installed on the nerve behind the lateral head of the fibula. The extent of initial excitation of the nerve fibres within the superficial region of the deep peroneal branch elicited by a monopolar half-cuff electrode was predicted. In the past 6 months two systems were implanted. In both patients significant improvements of gait dynamics were observed.

Multielectrode spiral cuff for ordered and reversed activation of nerve fibres.

In this paper we present the modelling, design, and experimental testing of a nerve cuff multielectrode system for selective activation of fibres in superficial peripheral nerve trunk regions which is capable of activating fibres in physiological order. The multielectrode system consists of 45 platinum electrodes embedded within a self-curling spiral silicone sheet organized in fifteen longitudinal groups consisting of three electrodes spaced equidistally around the circumference of the cuff. Electrodes in the centre band acted as stimulating cathodes while the two electrodes of the same group in the two outer bands were connected together and corresponded to the position of a particular cathode, serving as anodes to block the nascent action potentials by membrane hyperpolarization. The interpolar distance was 6 mm on both sides, resulting in a total cuff length of about 20 mm. The cuff was constructed with a diameter to fit the size of the dog sciatic nerve. Preliminary animal testing of the nerve cuff was performed on the sciatic nerve of a Bigley female dog. In the 45-electrode stimulation system, biphasic cathodic first pulses with quasitrapezoidal-shaped cathodic and square anodic parts were delivered through the particular group of tripolar electrodes to effect both selective stimulation of motor axons within the gastrocnemius muscle fascicle, and differential block by membrane hyperpolarization. The test was repeated using rectangular cathodic first biphasic current pulses delivered monopolarly on the central electrode of the same group while connected anodes were replaced by a common anode situated elsewhere in the surrounding tissue. In both experiments an isometric torque in the ankle joint elicited by the gastrocnemius muscle was measured and compared.(ABSTRACT TRUNCATED AT 250 WORDS)