A Finite Element Study

The advantages of using nerve cuff electrodes (NCE‟s) over surface or intramuscular electrodes are that NCE‟s have lower threshold currents, power efficiency, due it hold the stimulating contacts close to the nerve trunk and less power is used between the electrode and nerve trunk. Existing techniques for surgically or pharmacologically blocking the nerve have shown serious side-effects that could be permanently destructive to the nerve. The ability to use High frequency alternating current (HFAC) to initiate and reverse the block is promising; however, the technique requires large charge injection that could lead to nerve and electrode damage. Several designs such as the round spiral electrode or the flat interface nerve electrode (FINE) have shown such ability. However, charge density and charge per phase have been proven to be cofactors in neural injury induced by electrical stimulation. Using computer simulations we will test different hypothesis for minimizing the charge injection; like changing the cross section of a nerve from a round to a flat configuration, different contact separations, that implies different lengths of the cuff and different electrode types. Stimulating parameters like waveform, frequency also has an impact on the safety. The calculations involve a threedimensional finite element model to represent the electrical properties of the nerve and cuff. The blocking threshold was found to be significantly higher for the circular cuff than the flat cuff. The lowest threshold could be obtained with large contact separations. The results could facilitate designing of cuff electrodes to be used with HFAC for safe clinical applications. Keyword: nerve conduction block, charge density, electrical stimulation. En studie med finita elementmetoden av elektrodkonfigurationen för nervblockering