Comparison of threshold behaviour on long-term implantation of stimulating electrodes in longitudinal and transverse direction to the skeletal muscle
David, E.; Kaduk, B.; Mund, K.; Rao, J.R.; Richter, G.; Weidlich, E.
Biomedizinische Technik. Biomedical Engineering 32(10): 236-240
1987
ISSN/ISBN: 0013-5585 PMID: 3689863 Document Number: 293327
The application of implantable stimulating electrode within the scope of cardiac pacing, stereotactic pain treatment and other methods of stimulation is already routine today. Nevertheless, the influence of threshold is of importance to the efficiency of treatment with electrical stimulation. The threshold is determined by the minimum current leading to the excitation and contraction of the musculature. The electrical field distribution at the muscular membrane is decisive for excitability, and is in turn determined by an anisotropy of the electrical resistance in the vicinity of the electrode. The influence of anisotropy has been verified by an experimental investigation of the nature of excitability of skeletal muscle using pairs of glassy carbon electrodes implanted parallel and transverse to the direction of the fibre. Glassy carbon was used since it is an inert material and has less affinity towards the growth of connective tissue. On implantation of the electrodes a lower resistance was observed in the fibre direction than in transverse directions. After four weeks of implantation, the resistances of the electrodes become equal and decrease in general. The tissue alterations in the immediate vicinity of the electrode cannot be responsible for the change in resistance. The pathogenesis of the threshold change is discussed.