Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical energy applicator
Patent
1998-11-13
1999-11-16
Kamm, William E.
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical energy applicator
607152, 29825, A61N 105
Patent
active
059873612
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to the biomedical arts. It finds particular application in conjunction with cuff electrodes for stimulating nerves and will be described with particular reference thereto. It will be appreciated, however, that the present invention is also applicable to other types of implanted electrodes and biomedical devices.
Many types of nerve tissue damage do not heal. Such injuries leave a patient permanently without an appropriate nerve path for electrical signals or action potentials which travel from the brain to muscles or other biological tissue to cause a biological response. Similarly, such a discontinuity prevents action potentials from carrying sensory information or other biological feedback from the tissues to the brain. Moreover, there is also a tendency for action potentials to commence propagating naturally from below the injury site to the biological tissue causing an unconscious and unwanted biological response. Analogously, action potentials can propagate from above the injury site to the brain causing pain and erroneous sensory feedback.
Electrical potentials can be applied to nerve trunks and fibers to block the propagation of action potentials and for controllably initiating the propagation of action potentials in an upstream direction, a downstream direction, or both. Neural electrodes, such as illustrated in U.S. Pat. No. 4,602,624 to Naples, Sweeney, and Mortimer, and U.S. Pat. No. 5,324,322 to Grill, Jr., Creasey, Ksienski, Veraart and Mortimer controllably initiate and/or block action potentials in the nerves.
Although the prior art neural electrodes have proven effective, they do have drawbacks. Initially, certain types of prior art neural electrodes are labor intensive to manufacture, requiring the hand of a skilled fabricator to weld conducting wires to foil and fitting these foil conductors to silicone rubber coverings. Hand fabrication results in various problems, including the tendency of the foil conductors buckling when the metal-silicone structure is flexed. The flexure causes the foil to work harden and ultimately become a source for mechanical failure, stress corrosion, cracking and/or subsequent conduction failure.
Also, for neural electrodes whose patterns are formed with a metal deposition on a flexible substrate (e.g., silicone rubber or polyamide) there is a tendency for the metal to crack. The cracks on the surface appear as "cracked mud" at a microscopic level. Such cracks have the tendency to fill with uncured polymer when pressure is applied to a metal-polymer structure. This causes the uncontrolled formation of metal "islands," separated by the nonconducting polymer. Nonconducting polymer between "islands" eliminates electrical conduction along a trace by causing multiple open circuits.
The present invention provides a new and improved neural electrode and method of manufacture which overcomes the above-referenced problems and others.
SUMMARY OF THE INVENTION
A neural stimulating electrode comprises a sheet of metal foil having holes formed at predetermined locations. The holes are positioned to form patterns which allow the metal foil to flex without buckling when subjected to compressive forces. The holes also define a plurality of discrete electrodes on the metal foil when the foil is cut. A first polymeric base layer covers a first face of the metal foil. A second polymeric base layer covers a second face of the metal foil. The first and second polymeric base layers fill the holes in the metal foil. A third polymeric base layer covers both the first and second polymeric base layers. The third polymeric base layer has portions defining pairs of holes. Each pair of holes is associated with one of the discrete electrode structures. Each hole in each of the pairs of holes exposes a different portion of the discrete electrode structure for contacting tissue, passing current and/or measuring voltage.
In accordance with one aspect of the invention, the three polymeric base layers are laser cutable.
In accordance
REFERENCES:
patent: 4763660 (1988-08-01), Kroll et al.
patent: 4940065 (1990-07-01), Tanagho et al.
patent: 5324322 (1994-06-01), Grill, Jr. et al.
Axon Engineering, Inc.
Evanisko George R.
Kamm William E.
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